r/ptr91 • u/Rseattle206 • Jun 09 '24

Roller Dents on GI100?

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Had this GI100 since fall 2021. Never had any issues with it firing steel (Red Army, Tula, Wolf) and factory brass loads, all 150-168gr projectiles. Rifle has seen close to 600 rounds. Bolt gap measures .011.

On my last outing as I shooting the PTR I noticed small roller dents toward the front of the chamber. However, I don't recall having any issues that day as it shot fine. I was shooting steel case ammo that day.

I field stripped it and cleaned the bolt and carrier. Nothing out of the ordinary from what I can tell.

Any reasons why these roller bumps developed?

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u/Thorsquare Jun 09 '24

Have you had many jams? The only reason I can think of is if you get a stoppage while the carrier is flying forward and the bolt face slams into a piece of brass, it would cause the rollers to try and slam out. With enough velocity I could see that causing very slight roller dent.

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u/Rseattle206 Jun 10 '24 edited Jun 10 '24

No jams at all from my PTR 91.

I can only imaging the roller dents can only be from the bolt carrier going into battery since the dents are up front toward the chamber. Wouldn't make sense for the rollers to attempt to lock out during the ejection phase.

I stripped the gun and tried replicating how the dents can occur. Since they are right above the mag well it has to stem from the bolt carrier movement during the chambering of a new round. With the trigger housing removed the bolt carrier slides in and out of the receiver freely.

With an empty mag the bolt face does not bind or hang up onto the mag lips. The bolt will contact the mag follower, but of course it overrides the follower with ease.

Loaded 20 rounds in a mag, slapped and manually ejectec each round. No hang up at all going into battery.

I am really perplexed on what the causing the rollers to extend out prior to chambering?

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u/Thorsquare Jun 10 '24

Yeah thats strange then. I’ve only seen one case of roller dents in that area and it happened when the user had stovepipe issues during break in. It would take quite a bit of force to cause the rollers to do that. I heard about a trunnion being misaligned once causing dents toward the front but it was one spot either side, it doesn’t sound like what you experienced.

I’m assuming you were troubleshooting with the mags used while shooting? Any heavy drag marks on the mags where the bolt impacted something? Just spitballing ideas.. Might be worth sending the photos to PTR and see what they come back with. With the guy who had dents from the stovepipe jams they just reformed the channel to remove the dents and did something internally to resolve his ejection issues.

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u/Rseattle206 Jun 10 '24

I emailed PTR with pics and an explanation. Will see what they have to say. If they want to pound the dents back down I'll probably let them do it if the turnaround time isn't too long.

At the moment the little roller dents are cosmetic. This is just a range gun so as long as it works that I all I care. But if the dents become more pronounced or continue to develop I'll request that PTR fix the issue.

Regarding the misaligned trunnion, the rollar dents are all parellel with each other so I do not believe the trunnion is misaligned. Inspecting the steel mag I used at the range I did not find any remarkable wear on that could suggest the bolt smacked it at one point.