POF Roller Cam Upgrade?

[wahoo95]

Maybe I missed it, did this happen on a piston or DI gun? It’s amazing that, after unlocking, the bolt face can still be hit with such force to cause the cam pin to impact the upper like that. Just goes to show how complex the operation of these simple machines really are.

I'd have to see that happen in other examples before settling on a decision. Mine hasn't shown anything like that over the course of several thousand round rounds.

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[crosseyedshooter]

I'd have to see that happen in other examples before settling on a decision. Mine hasn't shown anything like that over the course of several thousand round rounds.

If it’s not happening during extraction, then it’s happening during chambering of the round. I’m just trying to imagine what the sequence of events are to cause the receiver damage in the photo.

[Jonnyt16]

I’d roll it right into the trash can. Another solution in search of a problem from a questionable company IMO.

Agreed. I wouldn't own anything remotely related to POF.

Care to elaborate? Asking because I was close to pulling the trigger on one of their Renegade models. Always thought POF was good to go. What am I missing?

[wahoo95]

Care to elaborate? Asking because I was close to pulling the trigger on one of their Renegade models. Always thought POF was good to go. What am I missing?

You may grow old waiting on true answer

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[mig1nc]

They cause extra damage if used in carbines and SBRs running cans.

Increased duration of pressure spike blows through chamber against the bolt face after unlock and causes the BCG to be pushed to the rear, tipping the cam pin into the inside of the upper.

Having the total surface area of the pin reduced from the flat fixed pin to a much smaller contact surface of the round pin creates a nice divot right behind the cam pin relief cutout. And no, i'm not talking about the typical wear leading into the relief cutout that most people complain about.

Might work better in non-suppressed platforms.

Wouldn't an adjustable gas block, dedicated gas port, or gas port insert, resolve that problem though?

[GrumpyM4]

Grumps, that's from a POF cam pin??

Yes. In an HK.

[GrumpyM4]

Maybe I missed it, did this happen on a piston or DI gun? It’s amazing that, after unlocking, the bolt face can still be hit with such force to cause the cam pin to impact the upper like that. Just goes to show how complex the operation of these simple machines really are.

Best I can figure is that when shooting suppressed (which I do quite often) there's enough residual bore/chamber pressure after unlock to shove the bolt rearward faster then the carrier is moving which in turn forces the cam to the side and impacting the receiver.

[GrumpyM4]

If it’s not happening during extraction, then it’s happening during chambering of the round. I’m just trying to imagine what the sequence of events are to cause the receiver damage in the photo.

Two places the cam pin would have cause to impact the inside of the receiver like that. Where the cam pin is located when it comes into contact with the rear of the top round in a magazine and the bolt has to overcome the inertia of the top round being held in the magazine, and then where the extractor has to over ride the rim of the case during the chambering phase of operation.

Seeing as how the cam is clear of the receiver at that point, I doubt it's happening during chambering.

[GrumpyM4]

Wouldn't an adjustable gas block, dedicated gas port, or gas port insert, resolve that problem though?

It's an HK. I do have an AGR, but I won't use it at this point. I SBR'd the gun, chopped the barrel to 10.5, and modded the gas port to run with a factory 16" gas block.

I opened the port just far enough to pass the lock back test so I can run it suppressed without making the bolt speed excessive. I took the POF roller cam out and the damage seems to have stabilized.

[panzerr]

Yes. In an HK.

Wow. There goes their theory about preventing upper receiver damage. Thanks for busting that one!