HK 91/G3/PTR91

[Forgetful Coyote]

Hey yall, just curious if anyone knows how long the receiver/bolt/etc will last before needing replacement/maintenance on HK91's/PTR-91's/etc..?? Any restrictions on projo weight or possibly a window in which you have to use say, for instance, 150-185gr rounds? Or can you run mostly whatever load combo ya want ala a AR15 provided its mag length?

Thanks yall,
FC

 

[W54/XM-388]

You usually don't need to worry about the receiver / bolt unless you are putting in a F/A trigger pack.
I've run the PTR-91 with both factory 155 and 175 without any issues.

Just don't expect this to be a "precision" rifle without spending a fortune.
Also on the "clones" such as the PTR-91 and some of the other ones, there are sometimes build quality issues.

 

[Son of Dorn]

The receiver on a G3 (and its clones/civilian models) is a single piece of stamped-and-folded steel, so... I don't actually think you can replace it, except for buying a new one. But I don't think you'll live long enough to need to, either. Rollers on the bolt and/or the barrel, around 10K rounds before you might want to think about replacement.

For ammo, I suggest sticking to mil-spec 7.62 NATO, either new production or surplus (there's lots of the latter out there, try to stick with US or German but other European countries or Israeli should be OK too). M80 or M118 or their non-US equivalents. Like @W54/XM-388 said, a basic G3-type will not be a "precision" rifle without rebuilding it into one of the dedicated configurations (PSG1, MSG90, G3SG/1, etc) and that'll cost you a fortune just for the right stock sometimes.

 

[tsavo303]

With a stock g3 or hk91. Stick with 147-150 gr fmj. I didn’t see improvement with match ammo. Some hunting ammo went to 8” group size at 100yds while cheap ball was about 2”
My ptr is functional equivalent of my hk91. I also had a msg parts kit rifle I sold. Wasn’t that accurate

 

[Constructor]

Try the 130gr SOST. As always accuracy depends on the barrel and adjusting the correct headspace and lock time. I built 1 about 20 years ago with a HK barrel, 2" was normal with most 147-149fmj but the 130 SOST shot closer to 1.25 off the bench.

 

[308ftWIN]

Started out as a GI model, have slowly made upgrades to turn it into a much better shooter. 1MOA is certainly possible with good ammo, although I do that rarely since the rifle is so hard on brass, even with a port buffer. Really fun to shoot at distance. Was actually a lot more capable at 1,000 with 175gr FGMM than I could have ever hoped for. Maybe some cheaper Prvi 168 match could be a good fit for it without making me feel bad.

Upgrades:

Heavy Buffer
HK21 buttpad
Triggerwork by Bill Springfield
Cheekpad
Port Buffer to save my brass if I can find it 20ft away instead of 40ft away.
HK Wide Forend
HK Bipod, love how it locks up into the forend.

My old Nikon is pictured, but it's now wearing a Cabela's Covenant Tactical 4-16

 

[Son of Dorn]

Started out as a GI model, have slowly made upgrades to turn it into a much better shooter. 1MOA is certainly possible with good ammo, although I do that rarely since the rifle is so hard on brass, even with a port buffer. Really fun to shoot at distance. Was actually a lot more capable at 1,000 with 175gr FGMM than I could have ever hoped for. Maybe some cheaper Prvi 168 match could be a good fit for it without making me feel bad.

Upgrades:

Heavy Buffer
HK21 buttpad
Triggerwork by Bill Springfield
Cheekpad
Port Buffer to save my brass if I can find it 20ft away instead of 40ft away.
HK Wide Forend
HK Bipod, love how it locks up into the forend.

My old Nikon is pictured, but it's now wearing a Cabela's Covenant Tactical 4-16

Nice. Ever consider going to the metal trigger housing?

 

[Holescreek]

Like all military rifles all of the above mentioned brands are overgassed on purpose to ensure function in the worst environments. The bolt opening delay is regulated by the angle of the locking piece. PTR mimmicked HK by using a 45 degree LP. If you're OK with the recoil and accuracy as is, leave it in there. If you want more consistent groups and a more pleasant recoil experience shooting heavier bullets you should change out to a 36 degree LP, or at least a 40 if you're concerned about function below freezing temps. If you shoot suppressed you will need a 36 to keep the rifle from beating itself to death on the buffer anyway. I shoot 168 gr SMK/44gr Varget through my target Cetmes with 37 degree LP's installed. I use the 37's all year long (Ohio winters/summer temps) with no ill effect on function.

 

[308ftWIN]

Nice. Ever consider going to the metal trigger housing?

If I was going to do anything, I'd probably add the Magpul stock. A metal housing and a palmshelf grip would be sweet too. Someday maybe.

 

[shoobe01]

The biggest arsenal maintenance thing for HK steel receivered guns is receiver stretch. The locking shoulders are in the receiver, some distance back from the barrel. After say 10,000 rounds, stick some feeler guages in and re-check bolt gap. Some say rollers wear, but most I see are replaced with the next size up to keep headspace as the system wears and stretches.

At maybe 1-200,000 rounds — for well, maintained, German factory made guns — you will run out of locking rollers, then can toss it, or get the thing rewelded. HK used to do it (not for YOU, but large agencies and armies), a few US smiths still do it I believe. Grind out the locking thingy, reweld it a bit closer. KSC security did it to their entire fleet of MP5s some time back, covered in detail... somewhere. SAR maybe.

So: They last FOREVER for any off us, not doing full auto practice every day. If you have the money, once worn out you just get them fixed up. Cockroaches and HKs will inherit the earth.

 

[W54/XM-388]

The biggest arsenal maintenance thing for HK steel receivered guns is receiver stretch. The locking shoulders are in the receiver, some distance back from the barrel. After say 10,000 rounds, stick some feeler guages in and re-check bolt gap. Some say rollers wear, but most I see are replaced with the next size up to keep headspace as the system wears and stretches.

At maybe 1-200,000 rounds — for well, maintained, German factory made guns — you will run out of locking rollers, then can toss it, or get the thing rewelded. HK used to do it (not for YOU, but large agencies and armies), a few US smiths still do it I believe. Grind out the locking thingy, reweld it a bit closer. KSC security did it to their entire fleet of MP5s some time back, covered in detail... somewhere. SAR maybe.

So: They last FOREVER for any off us, not doing full auto practice every day. If you have the money, once worn out you just get them fixed up. Cockroaches and HKs will inherit the earth.

For the rest of the mortals, keep your HK for the special times and then stick your F/A trigger pack on a well made clone receiver that you can use, abuse and then move on to the next one. If you can afford the F/A trigger pack then you can probably afford a bunch of well made clones to use it with.

 

[Holescreek]

The biggest arsenal maintenance thing for HK steel receivered guns is receiver stretch. The locking shoulders are in the receiver, some distance back from the barrel. After say 10,000 rounds, stick some feeler guages in and re-check bolt gap. Some say rollers wear, but most I see are replaced with the next size up to keep headspace as the system wears and stretches.

At maybe 1-200,000 rounds — for well, maintained, German factory made guns — you will run out of locking rollers, then can toss it, or get the thing rewelded. HK used to do it (not for YOU, but large agencies and armies), a few US smiths still do it I believe. Grind out the locking thingy, reweld it a bit closer. KSC security did it to their entire fleet of MP5s some time back, covered in detail... somewhere. SAR maybe.

So: They last FOREVER for any off us, not doing full auto practice every day. If you have the money, once worn out you just get them fixed up. Cockroaches and HKs will inherit the earth.

There is no "receiver stretch".

The bolt gap closes over a long period of time (if the rifle was properly built) as the forward window in the bolt head and the shoulders of the locking piece get indented from the constant peening of the much harder rollers. The bolt head and LP are essentially "wear items" to save the trunnion from damage. Additionally, the barrel can also shift forward inside the trunnion further closing the bolt gap.

There are 6 "minus sized" rollers and 10 "plus sized" used to keep the gap within the .004" to .020" specification. The gap has nothing to do with headspace, it's to position the bolt locking lever on the carrier to the bolt head for proper spring tension.

If you happen to have gotten a turd and the +10 rollers aren't large enough, the correct method of repair is to remove the barrel, rotate it 120 degrees and press it back into the trunnion at the proper depth to reset the gap before pinning it back into place. No welding required.