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Heckler & Koch G3 / PTR-91

• moderate
• Shop tier 2
• medium confidence
• Rifle
• roller delayed
• fluted chamber
• battle rifle
• push pin receiver

field strip ~3 min · reassembly ~5 min · detail strip ~40 min

Specifications

Model-specific safety

• Bolt gap is a real measured dimension on a roller-delayed action and determines whether the rifle is safe to fire. It is checked with feeler gauges against a specification and corrected by fitting a different locking piece. Worn rollers or an out-of-spec locking piece can let the action unlock too early. This is armorer work.
• Never ride the cocking handle forward. Pull it fully back and let it slam home.
• Rollers, locking piece, and bolt head are a fitted set. Do not mix parts between rifles.
• The fluted chamber marks brass heavily by design. That is not a fault and the flutes must not be polished out.
• The recoil spring assembly is under compression when the stock is removed.

Under spring tension

• Recoil spring assembly
• Hammer spring in the trigger group
• Magazine spring

Easily lost parts

Push pins · Rollers · Locking piece · Firing pin and spring

Tools

No tools required for the field strip.

Shop difficulty

Shop tier 2 Tier 2 — moderate among rifles and carbines, for the full job: strip to the parts that get coated and put it back together working. PTR's list has 71 key numbers (76 pieces) including the trigger pack. The barrel stays pressed and pinned in the receiver, so the work is the trigger pack (hammer, pressure fork, springs), the bolt head rollers, the cocking support roll pin, and a rear sight with loose balls and springs. Bolt gap must be measured after reassembly. Several traps but nothing timed.

Parts: 71 numbered parts (PTR-91 GI complete rifle incl. trigger pack internals and bolt group (76 pieces)), from PTR Roller-Delayed Blowback Weapon Systems Owner's Manual, Models .308 and 7.62x39 — PTR Industries, Inc., pp. 12-13 (PTR Firearm Exploded View/Par ptr-us.com [2].

Bench time: about 55 min to strip, 80 min to rebuild (estimate). Estimate: field strip, trigger pack (hammer, pressure fork and spring, sear, trigger, ejector, safety), mag catch and release lever, cocking lever and support (clamping sleeve), cocking tube cap, rear sight drum and base (balls/springs), front sight, handguard, flash hider, stock and back plate, bolt head and carrier. Rebuild longer for the trigger pack springs, rear sight detents and the bolt-gap

Small parts: 13 pins, 12 springs, 1 detents or plungers (counted from the PTR parts list in partCount)

What comes off for coating

• Trigger pack / grip: hammer, pressure fork and hammer spring, trigger, sear, trigger spring, sear spring, bushing and pins, ejector, pivot and spring, safety selector and shaft, pistol grip — roll-pin punches
• Receiver: magazine catch, push button, contact piece, spring, clamping sleeve, mag release lever and bushing, charging lever, support and elbow spring (H groove pin), cocking tube cap, compression bolt and contact spring, rear sight drum, base, springs, balls, screw, front sight holder/blade and clamping sleeve, flash hider, handguard and pin — HK rear sight tool, roll-pin punches
• Bolt group and stock: bolt head, extractor, spring and clamping sleeve, rollers and retainer, locking piece, firing pin and spring, back plate, buffer, recoil spring and rod, buttstock and pins

Special tools

• HK rear sight adjustment tool — Rear sight drum removal
• Roll-pin punches (2 mm, 2.5 mm, 4 mm) — Clamping sleeves in the trigger pack, mag catch, front sight, cocking support
• Feeler gauges — Bolt gap
• Flash hider wrench — Flash hider/spring ring

Known pain points

• PTR stops the owner at the bolt group and sends any further strip (trigger pack, cocking support, sights) to a gunsmith. (both)
  Source: PTR Roller-Delayed Blowback Weapon Systems Owner's Manual, Models .308 and 7.62x39 — PTR Industries, Inc. ptr-us.com [2] — “No further disassembly of the firearm is either necessary, or recommended, beyond this point.”
• The bolt head has to be clocked to the locking lever, rollers squeezed in and turned to the slot before the carrier goes back. (reassembly)
  Source: PTR Roller-Delayed Blowback Weapon Systems Owner's Manual, Models .308 and 7.62x39 — PTR Industries, Inc. ptr-us.com [2] — “squeeze the bolt head rollers into the bolt head to move the bolt head forward slightly”
• The rear sight drum sits on loose springs and plungers, and the sight base on a ball and spring; they are not captive and fly when the drum comes off. (both)
  Source: MP-5 Armorers Instruction — Heckler & Koch, Inc. International Training Division archive.org [3] — “WATCH THE SPRINGS AND PLUNGERS UNDER THE TOOL, THEY ARE NOT CAPTIVE”
• The cocking handle support is held by a clamping sleeve (roll pin) that only lines up with both holes in one handle position. (both)
  Source: MP-5 Armorers Instruction — Heckler & Koch, Inc. International Training Division archive.org [3] — “When the clamping sleeve is centered in the top access hole it is not in alignment in the bottom hole.”
• HK's own armorer kit for the G3 includes straightening mandrels for the stamped receiver and cocking tube, plus gauges for symmetry and headspace. (both)
  Source: G3 Armorer's Manual, Instructions for Maintenance and Repair, Cal. 7.62 mm x 51 — Heckler & Koch archive.org [4] — “Straightening mandrel for cocking lever housing”

Fit or check on rebuild

• Bolt gap — Measured with feeler gauges after reassembly; out of range means roller/locking piece work
  Source: PTR Roller-Delayed Blowback Weapon Systems Owner's Manual, Models .308 and 7.62x39 — PTR Industries, Inc. ptr-us.com [2] — “Safe, reliable, and acceptable bolt gap measurements for ALL PTR products after break-in will fall between .010”-.018” (.254 mm- .457mm).”
• Rear sight zero — The drum and base come off and the rifle must be re-zeroed
• Trigger function — Pressure fork and hammer spring seating checked with a function check

This is Pew-Takedown's rating, not the manufacturer's. How tiers are rated. Forum reports are owners' experience, not specifications.

Procedures

Torque specifications

No sourced torque values from the manufacturer are recorded for this firearm. Where a fastener has a specified torque — action screws, scope bases, muzzle devices, barrel nuts — get it from the manufacturer or a gunsmith rather than estimating it.

What the manufacturer does say: The manufacturer's documents give no torque value. They say: "Once the correction has been completed, tighten the Phillips head rear sight clamping screw back down." (PTR Roller-Delayed Blowback Weapon Systems Owner's Manual, Models .308 and 7.62x39, PDF p. 10 (windage adjustment))

Function check

• Verify the rifle is unloaded with no magazine inserted before each step.
• Pull the cocking handle fully rearward and release it sharply. The bolt should go fully into battery.
• With the selector on safe, press the trigger. The hammer must not fall.
• Move to semi-automatic, cock the action, and press the trigger. The hammer should fall.
• Hold the trigger back, cock the action, and release to feel the disconnector reset.
• Confirm both push pins are seated and the stock and trigger group are secure.
• If the bolt does not go fully into battery, do not fire. Have the bolt gap checked.

Maintenance

Lubrication points

• Bolt carrier exterior
• Locking piece ramps
• Rollers and their recesses
• Receiver interior
• Hammer and sear pivots

Cleaning notes

Clean the fluted chamber but never attempt to polish the flutes out — they exist to float the case on a gas layer so a delayed-blowback action can extract. Keep the roller recesses and locking piece ramps clean and lightly lubricated.

Suggested inspection interval: roughly every 1000 rounds. This is a general guideline, not a manufacturer specification.

Wear parts to inspect

Rollers (flats and chipping) · Locking piece · Bolt head · Extractor and spring · Recoil spring

Common issues

Also covers

The procedures above are reported to apply to: G3A3 and G3A4 · HK91 · PTR-91 · CETME Model C (related design). Verify against the manual for your specific model.

Similar manual of arms

• Heckler & Koch MP5
• FN FAL

Sourcing