It will not go back together

113 documented ways a firearm in this database resists reassembly, and what is actually wrong. Search by what you are seeing — "slide", "bolt will not", "pin" — or by the firearm.

Before anything else Stop and confirm the firearm is unloaded, again. A part that will not seat is a reason to put it down and read, not to push harder. Forcing a component is how firearms get damaged and how people get hurt.

113 problems

The firing pin retaining pin will not go in.

AR-15 (M16/M4 Pattern) · AR-15 Pattern (multiple manufacturers) high confidence

Why The cam pin is missing, or is in but not rotated 90 degrees.

Fix Drop the cam pin into its hole and rotate it a quarter turn, then seat the firing pin and fit the retaining pin.

Forcing it Never force the firing pin. If the cam pin is unrotated the bolt cannot lock and the rifle is unsafe to fire.
The cocking handle will not pull out of the breech bolt.

Beretta 1301 · Beretta high confidence

Why The bolt head is not pressed far enough for the groove on its neck to line up with the edge of the bolt body.

Fix Press the bolt head in until that groove aligns, hold it there, and pull the cocking handle straight out — once it is aligned it comes free with a firm tug.

Forcing it If it feels immovable, it is not aligned. Levering at it bends the handle.
The barrel will not come off, or the piston fell out with it.

Beretta 1301 · Beretta high confidence

Why The carrier stop pin was not pressed down first, or the piston was not held inside the gas cylinder.

Fix Press the carrier stop pin all the way down, pull the breech bolt back so it stays open, then hold the piston in the gas cylinder as you draw the barrel off.
The slide will not come off the frame.

Beretta 92FS · Beretta high confidence

Why The disassembly latch release button is not pressed while the lever rotates.

Fix Press the disassembly lever release button with your forefinger and rotate the lever downward with your thumb until it stops, then run the slide forward.
The bolt will not come out of the receiver.

Browning X-Bolt · Browning Arms Company high confidence

Why The safety is off. The X-Bolt releases its bolt with the safety ON.

Fix Leave the safety ON SAFE, press the bolt unlock button, rotate the handle up, then press the rear of the bolt stop on the left of the receiver.
The barrel will not turn to release the slide.

Colt Model 1903 Pocket Hammerless · Colt's Manufacturing Company high confidence

Why The slide is not at Colt's indicator position.

Fix Move the slide rearward until the perpendicular line on the slide at the arrow point lines up with the front edge of the frame, then turn the barrel left.

Forcing it Forcing the barrel against its ribs while they are still engaged can peen the locking recesses.
The slide goes onto the receiver but binds, or the pistol will not cycle.

Colt Model 1903 Pocket Hammerless · Colt's Manufacturing Company high confidence

Why The forward end of the retractor spring did not enter its recess in the lower part of the slide.

Fix Take the slide back off and refit it with the forward end of the retractor spring seated in its recess before drawing the slide back.

Forcing it Running the pistol with the retractor spring out of its seat bends the spring and its guide.
The barrel will not turn fully to the right on reassembly.

Colt Model 1903 Pocket Hammerless · Colt's Manufacturing Company high confidence

Why The slide is not at the indicator position, or the barrel ribs are not aligned with their recess.

Fix Draw the slide back to the indicator position and move the barrel very slightly until it engages, then turn it as far right as it will go.

Forcing it A barrel that is not turned fully right is not locked. Do not fire the pistol in that state.
The barrel will not go into the slide.

Colt Model 1903 Pocket Hammerless · Colt's Manufacturing Company high confidence

Why It is being offered up with the locking ribs in the wrong orientation.

Fix Enter the barrel with the locking ribs downward — visible as you look into the slide — then turn it more than a quarter turn so the ribs take up in the recess.
The base pin will not pull forward out of the frame.

Colt Single Action Army · Colt's Manufacturing Company high confidence

Why The base pin retaining catch is not held depressed, or this is a blackpowder-frame revolver whose base pin retaining screw is still fitted.

Fix Hold the catch on the left side of the frame depressed while pulling the pin. If the revolver has a screw in front of the frame instead, remove that screw first.

Forcing it Pulling against the catch or an unremoved screw bends the catch and scores the pin.
The cylinder will not come out, or catches on the way.

Colt Single Action Army · Colt's Manufacturing Company high confidence

Why It is being brought out past the loading gate and the ratchet is fouling it.

Fix Take the cylinder out to the right of the frame, easing it clear so the ratchet never touches the loading gate.

Forcing it Colt calls this contact out specifically. It damages the ratchet and the gate.
The cylinder is back in but will not rotate freely.

Colt Single Action Army · Colt's Manufacturing Company high confidence

Why The base pin is not fully home, or the cylinder is not correctly seated with the hammer at half-cock.

Fix Bring the hammer to half-cock, reseat the cylinder from the right, push the base pin fully home and secure it, then check rotation again before closing the gate.

Forcing it Firing with the cylinder not free to index is dangerous.
The hammer will not settle into the safety notch.

Colt Single Action Army · Colt's Manufacturing Company high confidence

Why It is being taken to the safety position directly from half-cock or full cock without releasing the trigger completely.

Fix Release the trigger fully first. Then with the thumb on the spur and the finger off the trigger, draw the hammer back about a quarter inch and ease it forward at the click.

Forcing it Colt warns the safety notch may not engage correctly otherwise — on a revolver with no transfer bar, that is the difference between safe and not.
The slide will not go back onto the frame.

CZ P-10 C · Česká zbrojovka (CZ) high confidence

Why The trigger is forward. On the P-10 the trigger must be held to the rear before the slide goes back on.

Fix Pull the trigger to the rear and hold it there, then fit the slide.

Forcing it CZ states that with the trigger forward the frame collides with the protrusion on the trigger bar. Forcing it damages the trigger bar.
The slide stop will not come out during takedown.

CZ P-10 C · Česká zbrojovka (CZ) high confidence

Why The slide is retracted too far, or not far enough. CZ specifies moving it back no more than 5 mm.

Fix Let the slide forward, pull the trigger so it stays rearward, then move the slide back only about 5 mm and press the disassembly plate down.
The slide will not pull forward off the frame.

FN 509 · FN Herstal high confidence

Why The striker has not been released, or was inadvertently recocked.

Fix With the chamber verified empty and the muzzle in a safe direction, keep the rear of the slide and frame aligned and press the trigger to release the striker, then pull the slide forward.
The barrel will not come out of the slide.

FN 509 · FN Herstal high confidence

Why It is being lifted straight out. The 509 barrel clears the extractor first.

Fix Grasp the barrel by its lug, lift it up and around the extractor, then slide it rearward out of the slide.
The slide will not go back onto the frame.

FN Five-seveN · FN Herstal high confidence

Why One of FN's three preconditions is unmet: the takedown lever must be rearward, the frame must hold no magazine, and the hammer must be cocked.

Fix Check all three, then hold the slide parallel above the frame and align its rear with the front of the frame's rear guide rails.
The barrel sits in the slide but feels loose, or accuracy has fallen off.

Heckler & Koch Mark 23 · Heckler & Koch high confidence

Why The O-ring near the muzzle is worn or missing. It is what holds the barrel tight in the front of the slide during firing.

Fix Fit a new O-ring. HK treats it as an inspect-or-replace item at every strip.

Forcing it A loose barrel is a accuracy problem, not a safety one, but it will not improve on its own.
The recoil/buffer spring assembly will not seat.

Heckler & Koch Mark 23 · Heckler & Koch high confidence

Why The guide rod has been put into the large hole meant for the barrel, or the angled locking surfaces are not aligned with those on the barrel locking block.

Fix The barrel goes through the large hole, the guide rod into the smaller one. Then align the opposing angled surfaces and push the rear of the assembly forward until the retainer catches the shelf on the locking block.
The slide release will not go back in.

Heckler & Koch Mark 23 · Heckler & Koch high confidence

Why The recess in the left side of the slide is not centred on the axle hole.

Fix Retract the slide until the recess lines up, hold it, and insert the slide release left to right until flush and locked.
The thread protector will not thread back on, or spins without tightening.

Heckler & Koch Mark 23 · Heckler & Koch high confidence

Why It has been cross-threaded or overtightened previously.

Fix Start it by hand counter-clockwise until you feel it drop into the thread, then turn clockwise until it stops. Do not force it.

Forcing it HK warns overtightening strips the threads.
The trigger group will not rotate up into the receiver.

Heckler & Koch MP5 · Heckler & Koch high confidence

Why The hammer is not cocked.

Fix Cock the hammer on the trigger group, then offer it up and rotate it into the receiver.

Forcing it Forcing it against a forward hammer bends the trigger group housing and the selector shaft.
The bolt head will not snap onto the locking piece.

Heckler & Koch MP5 · Heckler & Koch high confidence

Why The locking piece is not pressed fully into the carrier and turned to its assembly position, or the bolt head is not offered up with the extractor upwards.

Fix Press the locking piece fully in and hold it, turn it a quarter turn counter-clockwise, then fit the bolt head extractor-up and turn it a quarter turn counter-clockwise until it audibly snaps.
The gun goes together but does not lock up properly, or headspace feels wrong.

Heckler & Koch MP5 · Heckler & Koch high confidence

Why The locking piece has been fitted upside down.

Fix Strip the bolt group and refit the locking piece with its smooth side toward the bottom of the bolt.

Forcing it HK warns that improper assembly of this action compromises safety and functioning. Do not fire it to find out.
The handguard will not come off, or will not go back on.

Heckler & Koch MP5 · Heckler & Koch high confidence

Why It is being pulled straight off or pushed straight on.

Fix To remove, pull it towards the muzzle and then downwards. To fit, place it on the receiver from below and press it rearwards before inserting its pin.
The barrel will not come out of the slide.

Heckler & Koch P30 · Heckler & Koch high confidence

Why It is being lifted straight up. An HK barrel does not lift out.

Fix Pivot the barrel slightly forward and press down on the barrel locking block through the ejection port.
The recoil spring assembly will not stay in the slide, or springs back out while fitting the barrel.

Heckler & Koch USP · Heckler & Koch high confidence

Why The angled locking surfaces on the rear of the guide rod are not aligned with those on the bottom of the barrel locking block, so the recoil spring retainer never engages its shelf.

Fix Seat the guide rod's front in the hole at the front of the slide, line up the opposing angled surfaces, then push the rear of the assembly forward until the retainer catches the shelf on the front of the locking block.

Forcing it Levering the assembly in against the barrel bends the guide rod.
The slide will not go back onto the frame.

Heckler & Koch USP · Heckler & Koch high confidence

Why The sear axle is protruding from the side of the frame, or the rear of the slide is not pressing the disconnector down.

Fix Check the sear axle is flush on both sides of the frame, then set the rear of the slide above the front edge of the frame and draw it back slowly so it presses the disconnector down as the frame inserts enter the slide grooves.

Forcing it Forcing the slide over a proud sear axle shears it.
The slide release will not go back in.

Heckler & Koch USP · Heckler & Koch high confidence

Why The slide is not held at the point where the recess on its left side sits over the axle hole.

Fix Retract the slide until the recess lines up with the hole, hold it there, and insert the slide release from left to right until flush.
A compact USP feels wrong after reassembly, or the slide short-cycles.

Heckler & Koch USP · Heckler & Koch high confidence

Why The USP9 Compact and USP40 Compact recoil springs have been swapped.

Fix The USP9 Compact spring is coloured red. Fit the one that belongs to the calibre.
The slide will not go back onto the frame.

Heckler & Koch VP9 · Heckler & Koch high confidence

Why The disassembly lever has been rotated back up before the slide was fitted.

Fix Leave the disassembly lever pointing down at six o'clock until the slide is on and drawn rearward, then rotate it counter-clockwise.
The pistol will not come apart at all.

Heckler & Koch VP9 · Heckler & Koch high confidence

Why A magazine is still in the well. HK's disassembly lever doubles as a disassembly safety.

Fix Remove the magazine. The lever will not rotate forward with one inserted.
The breech bolt will not come out.

Hi-Point 995 Carbine · Hi-Point Firearms high confidence

Why The thumb safety is still on. Hi-Point's procedure requires it in the off (fire) position for the bolt to be removed.

Fix Confirm the carbine is unloaded, push the thumb safety fully down to off, and continue the strip.

Forcing it Levering the bolt against an engaged safety bears on the sear and the bolt.
The firing pin, springs or retainer fell out of the breech bolt.

Hi-Point 995 Carbine · Hi-Point Firearms high confidence

Why The bolt carries them loose once the retainer is released, and it was turned over.

Fix Hold the bolt muzzle-down and refit in order: firing pin, firing pin spring and assist spring, then the retainer with its spring guide facing forward.

Forcing it Reassembling with the retainer reversed leaves the striker unsupported.
The main recoil spring flew out during disassembly.

Hi-Point 995 Carbine · Hi-Point Firearms high confidence

Why The breech bolt is under spring tension as it comes off the barrel.

Fix Recover the spring and check it is not kinked before refitting. Keep a hand over the bolt as it releases next time.

Forcing it This is why Hi-Point requires safety glasses for this strip.
A part flew out of the frame after the bolt was removed.

Hi-Point 995 Carbine · Hi-Point Firearms high confidence

Why The trigger was pulled with the breech bolt out. The sear is under spring tension with nothing retaining it.

Fix Recover the sear and sear spring. Refitting them involves holding the sear cam clear of the disconnect arm and is fiddly — Hi-Point documents it, but it is not part of a routine clean.

Forcing it Hi-Point warns against this explicitly.
The bolt will not come out of the receiver.

Howa Model 1500 · Howa Machinery high confidence

Why On a three-position safety the lever is pushed fully rearward, which locks the bolt.

Fix Move the safety to the MIDDLE position — still ON, but the bolt is free to open — then depress the bolt stop with the bolt part way back.
The return spring will not come out, or will not go back in.

IWI Galil ACE · Israel Weapon Industries high confidence

Why It is being pulled straight up. IWI's motion is forward first, then up.

Fix Push the spring slightly forward to clear its seat in the receiver, then lift it out — and reverse that to refit.
The bolt will not separate from the carrier, or will not go back in.

IWI Galil ACE · Israel Weapon Industries high confidence

Why It is being rotated the wrong way. Counter-clockwise releases it.

Fix To remove, rotate the bolt counter-clockwise and pull it out. To fit, install it in the carrier and pull it forward while it rotates until it stops.
The bolt carrier group will not enter the receiver.

IWI Galil ACE · Israel Weapon Industries high confidence

Why The bolt is not in its forward position, or the piston is not lined up with the gas cylinder.

Fix Push the bolt fully forward in the carrier, then enter the group with the piston directed at the gas cylinder and the rear end towards its groove.
The gas cylinder is fitted but moves, or the rifle short-strokes.

IWI Galil ACE · Israel Weapon Industries high confidence

Why Its guides are not in the slot above the chamber, or its front end is not seated in the opening below the front sight.

Fix Refit the cylinder guides into the receiver slot and its front end below the front sight, push forward, and confirm it is solid in the gas block before firing.

Forcing it A gas cylinder that is not seated will not direct gas correctly and can work loose under fire.
The sear mechanism will not go back into the body.

IWI Tavor X95 · Israel Weapon Industries high confidence

Why The hammer is not cocked.

Fix Cock the hammer, then place the sear mechanism in, close the bolt carrier stop lever, and push the locking pins home.

Forcing it Forcing it against an uncocked hammer bears on the sear housing.
The hammer was released while the sear mechanism was out.

IWI Tavor X95 · Israel Weapon Industries high confidence

Why Nothing was retaining it.

Fix Inspect the housing for damage before reassembling. IWI states this damages the housing, so it is not something to assume got away with.

Forcing it IWI names this specifically as a damage mode.
A locking pin came all the way out of the rifle.

IWI Tavor X95 · Israel Weapon Industries high confidence

Why It was pulled past its stop. IWI's instruction is to pull only until it stops.

Fix Re-enter the pin from the left and push it back through until it seats. Check it moves to its stop and no further next time.
The bolt carrier stop assembly came out of the rifle.

IWI Tavor X95 · Israel Weapon Industries high confidence

Why It was disturbed while the sear mechanism was removed.

Fix Hold the bolt carrier stop lever open with your middle finger, slide the head of the bolt carrier stop under the step of the insert, then push upwards so it snaps into place.
The bolt will not come out of the carrier.

IWI Tavor X95 · Israel Weapon Industries high confidence

Why The recoil mechanism is not set into its rearward position, so the bolt guiding pin is not clear.

Fix Pull the bolt rotation control bar rearward until it snaps into the removal notch in the buffer — the rear of the bar should protrude about 1.43 inches — then push out the bolt guiding pin.
The bolt will not go into the receiver or onto the bolt carrier.

Kel-Tec KSG · Kel-Tec CNC Industries high confidence

Why The forend is not cycled completely rearward, or the bolt is being offered up upright.

Fix Cycle the forend fully rearward, then insert the bolt on its side and rotate it 90 degrees upright so its rear lip drops into the square cutout in the bolt carrier.

Forcing it Forcing the bolt in upright bears on the bolt lip and the carrier cutout.
The forend goes forward but there is no click, or the action feels wrong afterwards.

Kel-Tec KSG · Kel-Tec CNC Industries high confidence

Why The bolt is not pushed fully forward on the bolt carrier, so it is not locking with the barrel extension.

Fix Pull the forend back, push the bolt completely forward until there is no gap at the mating surfaces, then run the forend fully forward and listen for the definitive click.

Forcing it Firing without the bolt locked to the barrel extension is dangerous. If you do not get the click, stop.
The stock will not go back in.

Kel-Tec KSG · Kel-Tec CNC Industries high confidence

Why The forend is not completely forward, or the lifter axes are out of place.

Fix Run the forend fully forward first, then seat the stock with the lifter axes in position. Lifting up on the firing pin during insertion helps, as Kel-Tec notes.
The grip assembly will not sit down, or the assembly pins will not push through.

Kel-Tec KSG · Kel-Tec CNC Industries high confidence

Why The forward part of the grip assembly is not under the grip catch, so the pin holes do not line up.

Fix Insert the front of the grip assembly under the grip catch first, rotate the grip down into place, and only then push the pins through from their retaining holes.
A gap shows between the barrel extension and the receiver after joining the two assemblies.

Kel-Tec KSG · Kel-Tec CNC Industries high confidence

Why The two magazine bolts are not fully or not evenly tightened.

Fix Alternate between the two bolts a half turn at a time until both firmly resist. They thread into the same piece, so uneven tightening binds them before they are home.

Forcing it A gap or any travel between the assemblies means the shotgun is not safe to fire.
The assembly pin will not go back in.

Kel-Tec P-3AT · Kel-Tec CNC Industries high confidence

Why The pin is being pushed in straight, or the assembly pin hole is not aligned with the cut in the barrel.

Fix Hold the slide back, let the barrel run forward, and look into the pin hole until you can see the barrel cut lined up. Then start the pin at a slight angle so it pushes the assembly pin spring down, and push it fully in.

Forcing it Driving the pin in straight bends the assembly pin spring.
The slide will not go back onto the frame.

Kel-Tec P-3AT · Kel-Tec CNC Industries high confidence

Why The barrel or the recoil springs are not centred in the slide.

Fix Take the slide off, re-centre the barrel and both recoil springs, and refit. Kel-Tec names this as the thing to get right on reassembly.
A small part fell out when the slide came off and the pistol will not now eject.

Kel-Tec P-3AT · Kel-Tec CNC Industries high confidence

Why That part is the ejector, #115. Kel-Tec warns it falls out freely once the slide is removed.

Fix Refit the ejector into its seat in the frame before pushing the slide back on. The pistol will chamber and fire without it and fail to eject, so do not skip it.

Forcing it Running the pistol without the ejector produces a stoppage on every shot.
The assembly pin spring is missing after disassembly.

Kel-Tec P-3AT · Kel-Tec CNC Industries high confidence

Why Pressure was not kept on the grip around the assembly pin while it was pulled.

Fix The spring is a service part. Contact Kel-Tec rather than substituting a spring of approximate size.
The stock pin will not go back in.

Kel-Tec SUB-2000 · Kel-Tec CNC Industries high confidence

Why The slot in the buffer assembly, the chosen stock position and the receiver are not all aligned at once.

Fix Press the buffer assembly forward against spring tension, line up the buffer slot with the stock position hole and the receiver, then push the pin through. Kel-Tec notes this takes some adjusting of the parts.

Forcing it Driving the pin against misaligned holes burrs the pin and the stock.
The stock pin is lost.

Kel-Tec SUB-2000 · Kel-Tec CNC Industries high confidence

Why It is not captive once removed, which Kel-Tec warns about in capitals.

Fix It is a service part from Kel-Tec. Do not substitute a pin of approximate diameter — it carries the buffer and recoil spring load.
The operating handle will not go back in.

Kel-Tec SUB-2000 · Kel-Tec CNC Industries high confidence

Why The hole in the bolt is not lined up with the operating handle slot in the receiver.

Fix Slide the bolt until the handle hole sits over the slot, then insert the handle fully before fitting the recoil spring.
The rifle is assembled but will not function, and the hammer was dropped during cleaning.

Kel-Tec SUB-2000 · Kel-Tec CNC Industries high confidence

Why The hammer was released with the bolt assembly out.

Fix Kel-Tec states this makes the rifle inoperable and it is not something to correct by feel. Have it looked at rather than forcing the action.
Parts flew loose while removing the stock pin.

Kel-Tec SUB-2000 · Kel-Tec CNC Industries high confidence

Why Positive contact with the buffer assembly was lost while it was under recoil spring tension.

Fix Recover the buffer assembly, recoil spring and stock pin, and restart the strip keeping a hand on the buffer throughout.

Forcing it This is the step on this carbine where eye protection matters.
The stock will not come off, or will not go back on.

M1 Carbine · Springfield Armory (U.S. Government Arsenal) high confidence

Why The safety is not pushed to the left, so the receiver is still caught on the stock abutment.

Fix Push the safety to the left, then raise the muzzle end of the barrel out of the stock — or lower it in, refitting.

Forcing it Levering the barrel out against the abutment cracks the stock at the recoil shoulder.
The upper band will not slide off.

M1 Carbine · Springfield Armory (U.S. Government Arsenal) high confidence

Why The upper band screw was not loosened, or the upper band retaining spring is not depressed.

Fix Loosen the screw about 1/8 inch — do not remove it — then depress the retaining spring with the base of a cartridge and slide the band off over it.
The guard assembling pin will not start, or the trigger group will not come free.

M1 Carbine · Springfield Armory (U.S. Government Arsenal) high confidence

Why The hammer is not cocked, or the trigger group is being pulled downward instead of sideways.

Fix Cock the hammer first by cycling the operating slide. Start the pin with the small end of the guide rod, then slide the trigger group to the left out of its undercut grooves.

Forcing it Driving the pin against a forward hammer burrs the pin and the trigger housing.
The operating spring will not go back into the receiver well.

M1 Carbine · Springfield Armory (U.S. Government Arsenal) high confidence

Why It is being pushed straight in rather than entered from the left with the guide rod raised.

Fix Fit the spring onto the guide rod, enter the spring into its well from the left, then seat the rod's end into its seat in the operating slide.
The stock group will not separate from the barrel and receiver.

M1 Garand · Springfield Armory (U.S. Government Arsenal) high confidence

Why The rifle is being tapped rather than struck, or the trigger housing group is still in place.

Fix Remove the trigger housing group first, then lay the rifle sights up with the muzzle left, raise it by the rear of the receiver and give a firm downward blow on the small of the stock.

Forcing it Prying at the joint splits the stock at the receiver abutment.
The follower rod and operating rod spring came apart.

M1 Garand · Springfield Armory (U.S. Government Arsenal) high confidence

Why They were separated during removal. FM 23-5 instructs that they are not to be separated.

Fix Reassemble the spring onto the follower rod before refitting, and withdraw them as one unit next time.
The operating rod will not come off, or will not go back on.

M1 Garand · Springfield Armory (U.S. Government Arsenal) high confidence

Why Its lug is not aligned with the dismount notch in the receiver track.

Fix Move the operating rod fore and aft until the lug sits at the notch, then rotate the handle outward to lift it clear — and reverse that to refit.

Forcing it Springing the operating rod to force it past the track bends it, and a bent op rod is a known accuracy and function problem on this rifle.
The trigger housing will not latch back in.

M1 Garand · Springfield Armory (U.S. Government Arsenal) high confidence

Why The housing is not seated in the stock and receiver before the guard is swung closed.

Fix Seat the trigger housing group fully, then swing the trigger guard closed until it latches. It should close without heavy force.
The slide stop will not go back in.

M1911A1 / 1911 Government Model · M1911 Pattern (multiple manufacturers) high confidence

Why The barrel link is not upright, so the slide stop pin has nothing to pass through.

Fix Stand the barrel link vertical and line the slide stop pin up with the hole in it before pressing the stop home.
The bolt will not come out of the receiver.

Remington Model 700 · Remington Arms high confidence

Why The safety is not in the "S" position.

Fix Place the safety in "S", raise the bolt handle, pull it fully back, then push the bolt stop release in the trigger guard.
The bolt will not close after reinstalling it.

Remington Model 700 · Remington Arms high confidence

Why The integrated security system is still engaged. That is a separate mechanism from the safety.

Fix Disengage the security system — the red dot shows when it is off — then push the bolt handle down.
The stock cracked, or the barrelled action will not come out cleanly.

Ruger 10/22 · Sturm, Ruger & Co. high confidence

Why The safety was not centred. If it is not in the middle when the barrel and receiver leave the stock, the stock is damaged.

Fix Position the safety so an equal amount of button shows on each side before lifting the action out.

Forcing it Ruger states plainly that an off-centre safety damages the stock during removal.
The takedown screw will not come all the way out.

Ruger 10/22 · Sturm, Ruger & Co. high confidence

Why It is not meant to. Ruger's procedure loosens it, not removes it.

Fix Loosen the takedown screw with an Allen wrench and leave it in the stock.
The barrel assembly will not rotate far enough to lock, or the locking lever does not line up with the magazine well.

Ruger 10/22 Takedown · Sturm, Ruger & Co. high confidence

Why The adjustment knob is tightened too far, or the bolt is not locked back.

Fix Lock the bolt back, then loosen the adjustment knob clockwise, seat and rotate the barrel until the locking lever aligns with the magazine well, and retighten the knob counterclockwise.

Forcing it Ruger warns that firing without the barrel fully locked risks malfunctions, damage to the rifle, and injury or death.
The rifle goes together but the barrel has play at the joint.

Ruger 10/22 Takedown · Sturm, Ruger & Co. high confidence

Why The adjustment knob is backed off too far.

Fix Turn the adjustment knob counterclockwise — that is the tightening direction on this rifle — and recheck. Do not shoot a loose joint tight.

Forcing it A loose lock-up loses the rifle's return to zero and loads the joint unevenly.
Tightening the adjustment knob seems to make the barrel looser.

Ruger 10/22 Takedown · Sturm, Ruger & Co. high confidence

Why The knob is being turned the way most fasteners go. On the 10/22 Takedown the directions are reversed.

Fix Counterclockwise tightens, clockwise loosens. The Ruger PC Carbine's equivalent knob works the opposite way, which is a common source of this mix-up.
The barrel assembly will not come off even with the locking lever pushed forward.

Ruger 10/22 Takedown · Sturm, Ruger & Co. high confidence

Why The bolt is not locked to the rear.

Fix Lock the bolt back, then push the locking lever forward towards the muzzle and rotate the barrel counterclockwise.

Forcing it Twisting hard against a closed bolt bears on the locking lugs.
The bolt will not come out of the receiver.

Ruger American Rifle · Sturm, Ruger & Co. high confidence

Why The safety is off. Ruger specifies the safety ON if the firing pin is cocked.

Fix Put the safety in the SAFE position, open the bolt, and press the rear of the bolt stop — on the left of the receiver for a right-handed rifle, the right for a left-handed one.
The firing pin retaining pin will not go in.

Ruger AR-556 · Sturm, Ruger & Co. high confidence

Why The cam pin is missing, or it is in but not rotated 90 degrees, so it blocks the retaining pin's hole.

Fix Pull the firing pin, seat the cam pin in its hole and rotate it a quarter turn, then reinstall the firing pin and the retaining pin.

Forcing it Never force or trim the retaining pin. Without the cam pin rotated the bolt cannot lock, and the rifle is unsafe to fire.
The bolt carrier group will not slide back into the upper receiver.

Ruger AR-556 · Sturm, Ruger & Co. high confidence

Why The charging handle is not in its channel ahead of the carrier, or the bolt is not pushed forward into its unlocked position on the carrier.

Fix Insert the charging handle part way, push the bolt fully forward in the carrier, then feed the carrier key into the charging handle's track and slide both home together.
The upper and lower will not close, or the rear takedown pin will not seat.

Ruger AR-556 · Sturm, Ruger & Co. high confidence

Why The bolt carrier group is not fully forward in the upper, or the hammer is forward and fouling the carrier.

Fix Push the carrier fully into battery. If the receivers still will not close, cock the hammer before mating them.

Forcing it Forcing the receivers shut on a hammer bends the disconnector and hammer hooks.
The takedown pins are extremely stiff on a new rifle.

Ruger AR-556 · Sturm, Ruger & Co. high confidence

Why New receiver holes and detents are tight.

Fix Ruger's own instruction is to use a punch and gently tap the pin through. It becomes easier to remove over time.
The takedown pin will not go back into the frame.

Ruger LCP II · Sturm, Ruger & Co. high confidence

Why It is being pushed in straight. The pin has to displace its retaining spring first.

Fix Start the pin into the frame nose-down at about 45 degrees until its tip pushes the retaining spring down, then rotate it level with its hole and push it home.

Forcing it Hammering a straight-in pin bends the retaining spring and burrs the pin.
The slide will not sit down on the frame, or binds part way.

Ruger LCP II · Sturm, Ruger & Co. high confidence

Why The recoil spring assembly is not seated against the barrel lug, or the nested spring is in backwards.

Fix Lift the recoil spring assembly out and refit it with the flared end of the inner spring facing the muzzle and the rear of the guide rod against the barrel lug.
The barrel will not drop into the slide.

Ruger LCP II · Sturm, Ruger & Co. high confidence

Why It is being lowered straight down. The barrel has to go in at an angle.

Fix Enter the barrel forward and slightly up, then push it rearward into its locked position — the reverse of the forward, down and back motion that removed it.
The takedown pin went missing during cleaning.

Ruger LCP II · Sturm, Ruger & Co. high confidence

Why Unlike most striker pistols, the LCP II's takedown pin is not captive and leaves the frame entirely.

Fix Ruger sells the part; contact Customer Service with the pistol's model and serial. Do not substitute a pin of approximate size.
The barrel and receiver will not lift off the grip frame.

Ruger Mark IV · Sturm, Ruger & Co. high confidence

Why The barrel is being tilted the wrong way, so it binds on the bolt stop pin.

Fix Hold the barrel in one hand and the grip frame in the other, depress the take-down button, and tilt the BARREL downward so it clears the bolt stop pin. Then lift straight up.
The pistol will not go back together.

Ruger Mark IV · Sturm, Ruger & Co. high confidence

Why The safety is off. The Mark IV reassembles only with the safety ON, white dot fully visible.

Fix Put the safety on so the white dot shows, then align the receiver notch with the frame pivot pin and rotate down until it clicks.
The slide will not come forward off the frame after the takedown pin is out.

Ruger MAX-9 · Sturm, Ruger & Co. high confidence

Why The striker was re-cocked while handling the slide.

Fix Point the pistol in a safe direction, confirm again that it is unloaded, pull the trigger to drop the striker, and move the slide forward.

Forcing it Forcing the slide forward against a cocked striker bears on the striker block and the frame insert.
The takedown pin will not go back in, or will not sit flush.

Ruger MAX-9 · Sturm, Ruger & Co. high confidence

Why The takedown plate is not pressed fully down, or the slide is not held about 1/8 inch rearward, so the pin hole is not lined up.

Fix Press the takedown plate fully down, pull the slide back roughly 1/8 inch and hold it, then push the pin in until it is flush with the frame insert.

Forcing it Driving the pin against a misaligned hole burrs the pin and the frame insert.
The slide will not go back onto the frame at all.

Ruger MAX-9 · Sturm, Ruger & Co. high confidence

Why The barrel and guide rod assembly were not installed into the slide first.

Fix Take the slide back off, fit the barrel, then seat the guide rod against the barrel lug, and only then put the slide on the frame.

Forcing it Ruger warns specifically against installing the slide without them.
The guide rod will not stay in place while fitting the slide.

Ruger MAX-9 · Sturm, Ruger & Co. high confidence

Why The rear of the guide rod is not seated against the barrel lug.

Fix With the slide and barrel upside down, set the rear end of the guide rod against the barrel lug before turning the assembly over.
The trigger guard will not unlatch.

Ruger Mini-14 · Sturm, Ruger & Co. high confidence

Why The hammer is not cocked, or the safety is off. Ruger requires both hammer cocked and safety ON for disassembly.

Fix Pull the slide handle fully rearward and release it to cock the hammer, confirm the safety is ON, then lever the trigger guard open with a 1/4 in rod through the hole in its rear.

Forcing it Never use a cartridge as the lever. Ruger warns it can loosen the bullet in the case.
The barrel assembly will not go into the receiver, or will not rotate to lock.

Ruger PC Carbine · Sturm, Ruger & Co. high confidence

Why The bolt is not locked back with the bolt stop engaged, or the adjustment knob is screwed in too far.

Fix Lock the bolt back and engage the bolt stop, then try again. If it still will not seat, back the adjustment knob off counterclockwise, install the barrel, and retighten the knob.

Forcing it Forcing the barrel assembly against a closed bolt bears on the bolt face and the barrel block.
The barrel assembly goes in and locks, but feels loose or rattles.

Ruger PC Carbine · Sturm, Ruger & Co. high confidence

Why The adjustment knob is backed off too far. It sets the lock-up tension and stays wherever it was left.

Fix Remove the barrel assembly, tighten the adjustment knob clockwise a little, and reinstall. Ruger's target is noticeable resistance as the barrel turns in, without it being difficult.

Forcing it Firing with a loose barrel lock-up costs accuracy and puts the joint under loads it was not adjusted for.
The barrel assembly will not come out even with the locking lever pushed forward.

Ruger PC Carbine · Sturm, Ruger & Co. high confidence

Why The bolt is not locked back, or the assembly is being rotated the wrong way.

Fix Lock the bolt back, hold the locking lever forward, and rotate the barrel counterclockwise — the opposite of the direction that installed it.

Forcing it Levering on the barrel or forend to free it can bend the forend and mar the joint.
After reassembly the first shots group poorly.

Ruger PC Carbine · Sturm, Ruger & Co. high confidence

Why The barrel assembly has not been seated.

Fix With the rifle empty and no magazine, slingshot the bolt from fully rearward two or three times, as Ruger directs after every barrel installation.
The bolt will not go back into the receiver, or will not come out in the first place.

Ruger Precision Rifle · Sturm, Ruger & Co. high confidence

Why The stock is not folded. The buttstock sits directly behind the bolt's line of travel.

Fix Push the stock pivot lock button, fold the stock to the left, and rotate the stock pivot latch a quarter turn clockwise to lock it folded. Then work the bolt.

Forcing it Forcing the bolt against the stock or the bolt stop can peen the stop and the bolt lug.
The firing pin back has dropped down and the bolt shroud will not go back on at rest.

Ruger Precision Rifle · Sturm, Ruger & Co. high confidence

Why The firing pin back was rotated past the positions Ruger illustrates, so it fell to the bottom of the cocking cams.

Fix Rotate the firing pin back clockwise, through both cocking cams if necessary, until its lobe returns to the notch on the cam. Ruger warns this takes significant effort and possibly a gripping aid.

Forcing it Levering the shroud on over a dropped firing pin back can damage the cocking cams.
The bolt goes in but the rifle will not cock, or the firing pin does not release.

Ruger Precision Rifle · Sturm, Ruger & Co. high confidence

Why The bolt shroud was not rotated the full 30 degrees counterclockwise on reassembly, so the firing pin back is not locked at rest.

Fix Remove the bolt and confirm the lobe of the firing pin back sits in the notch on the cam, as Ruger illustrates, before reinstalling.
The slide will not go back onto the frame.

Ruger SR22 · Sturm, Ruger & Co. high confidence

Why The takedown lever has been returned to its locked position too early, or the hammer is down.

Fix Leave the takedown lever fully DOWN, push the safety lever up to expose the red dot, and cock the hammer with your thumb. Then fit the slide and lock the lever afterwards.
The recoil spring assembly will not seat.

Ruger SR22 · Sturm, Ruger & Co. high confidence

Why The spring is on the guide rod backwards, or the assembly is going into the slide rather than the frame insert.

Fix The recoil spring fits onto the guide rod small-diameter end first, and the assembly goes into the hole in the FRAME INSERT, not the slide.
The bolt will not come out of the receiver.

Savage Mark II · Savage Arms high confidence

Why You are looking for a bolt release lever. These rimfires do not have one — the trigger is the release.

Fix With the safety forward and no ammunition present, pull the trigger firmly and hold it while sliding the bolt out of the rear of the receiver.
The bolt will not go back in.

Savage Mark II · Savage Arms high confidence

Why The bolt handle is not aligned, the firing pin is not at top centre, or the trigger is not being held.

Fix Check the handle lines up with the bolt arm slot and the firing pin is top centre, then pull the trigger firmly with the safety off while sliding the bolt in. If it will not go, take it out and recheck alignment rather than forcing it.
The bolt binds partway and will not clear the receiver.

Savage Model 110 · Savage Arms high confidence

Why The trigger is not held fully rearward, or the cocking indicator is not pushed all the way down.

Fix With no ammunition present and the safety forward, pull the trigger fully rearward and HOLD it, push the cocking indicator down as far as it goes, then draw the bolt out.

Forcing it Savage's manual says the bolt seeming to bind is the sign this step was missed. Forcing it is how bolts and stocks get damaged.
The barrel will not seat back into the receiver.

Savage Stevens 320 · Stevens Arms high confidence

Why The bolt is fully open. Savage's procedure closes it about two inches first.

Fix Push the forend forward roughly two inches to close the bolt partly, then slide the barrel retaining lug over the magazine tube and seat the barrel.

Forcing it Forcing the barrel in against a fully open bolt can damage the breech face and the magazine tube threads.
The locking nut will not thread on, or cross-threads.

Savage Stevens 320 · Stevens Arms high confidence

Why The barrel is not fully seated in the receiver, so the nut is meeting the magazine tube at an angle.

Fix Back the nut off, seat the barrel completely with the bolt partly closed, then start the nut by hand and tighten it securely.

Forcing it Cross-threading the magazine tube is not a home repair.
The action will not cycle after refitting the barrel.

Savage Stevens 320 · Stevens Arms high confidence

Why The barrel is seated but the locking nut is not tight against it.

Fix Tighten the locking nut securely against the barrel, then cycle the action by hand before loading.
The bolt will not come out of the receiver.

Tikka T3x · Tikka (SAKO) high confidence

Why On a standard two-position safety, ON locks the bolt as well as the trigger.

Fix Move the safety to OFF, then press the bolt release. If your rifle has the optional three-position safety, close the bolt and move the lever back to ON instead, then press the release.
The takedown catch will not move.

Walther PDP · Carl Walther GmbH high confidence

Why It is being rotated. The PDP catch is gripped from above on both sides and pressed down.

Fix Squeeze the catch from above on both sides and press downwards, after releasing the striker with the trigger.
The recoil spring assembly will not seat in the slide.

Walther PDP · Carl Walther GmbH high confidence

Why It is in backwards. The two ends are not interchangeable.

Fix The small rod end goes into the spring mounting at the front of the slide; the large polymer end goes into the lower barrel recess.
The bolt will not come out of the receiver.

Winchester Model 70 · Winchester Repeating Arms high confidence

Why The safety is in the wrong position, or the firing pin is not cocked.

Fix Put the safety in its INTERMEDIATE position — not fire — and confirm the cocking indicator protrudes at least 1/8 in, then depress the bolt stop and withdraw the bolt.