Gemtech introducing suppressed bolt carrier

[oddballmkg]

My Gemtech bolt carrier broke over the weekend, it had about 500 rounds of Blackhills 77 grain OTM through it. Was being used on a 18 inch SPR type rifle with the Magpul PRS stock and Surefire suppressor. The something inside the gas setting cam broke allowing the cam to flop back and forth causing the rifle to jam/not cycle. And the cam also now falls out of the bolt carrier. A friend of mine shooting next to me also had the his Gemtech carrier fail the same way as mine. His also had about 500 rounds through it using the same type of rifle as mine.

[punkey71]

My Gemtech bolt carrier broke over the weekend, it had about 500 rounds of Blackhills 77 grain OTM through it. Was being used on a 18 inch SPR type rifle with the Magpul PRS stock and Surefire suppressor. The something inside the gas setting cam broke allowing the cam to flop back and forth causing the rifle to jam/not cycle. And the cam also now falls out of the bolt carrier. A friend of mine shooting next to me also had the his Gemtech carrier fail the same way as mine. His also had about 500 rounds through it using the same type of rifle as mine.

Are they on the way back to Gemtech for evaluation?


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[Joe Mamma]

My Gemtech bolt carrier broke over the weekend, it had about 500 rounds of Blackhills 77 grain OTM through it. Was being used on a 18 inch SPR type rifle with the Magpul PRS stock and Surefire suppressor. The something inside the gas setting cam broke allowing the cam to flop back and forth causing the rifle to jam/not cycle. And the cam also now falls out of the bolt carrier. A friend of mine shooting next to me also had the his Gemtech carrier fail the same way as mine. His also had about 500 rounds through it using the same type of rifle as mine.

Thanks for the update. If it's not too much trouble, I would love to see a picture of the break (in the part that falls out of the carrier).

Joe Mamma

[oddballmkg]

IMG_0381.jpg
See if this works for the picture. I got hit in the face by something coming out of the chamber just prior to the bolt failing. Looking at the cam, I do not see where they use a pin/spring dentent to hold the cam in. So there must be something with the gas tube fitting that puts pressures on the cam to keep it from rotating and coming out of the bolt. I have a second Gemtech carrier with about the same amount of rounds through it so far it seems ok.

[MSparks909]

Wow. Please keep us updated on how Gemtech handles the issue. I have 2 of these carriers for my in-progress pistol (and later SBR) builds. My cans are still in jail so I have time to potentially swap these out if necessary.

[Slippers]

The valve has a flange on one end, which has a short and long protrusion coming off opposite sides. The long side prevents the valve from turning while installed in your rifle because it will hit the inside of the upper receiver. The short side sits in a slot on the bolt carrier. This slot has an opening when at the 6 o'clock position, so that when you have the carrier outside of your rifle you can turn the valve 90 degrees and easily remove it. If the valve is fully turned to the suppressed or unsuppressed settings, then it cannot fall out since the short protrusion is engaged in the slot.

The valve with intact flange:



The valve with the long side of flange at 12, short side of flange at 6, allowing installation or removal from the carrier:



And the valve set to unsuppressed - note how the short side of the flange is slightly covered up by the carrier at the corner where the "S" is located.




The long side of the flange is leaving marks in the anodizing in my upper receivers, which means the motion of the carrier or the pressures on the valve during firing are trying to turn it. I have stopped using the SBC because of my previously mentioned issues where monopodding on a magazine causes malfunctions.

[MSparks909]

The valve has a flange on one end, which has a short and long protrusion coming off opposite sides. The long side prevents the valve from turning while installed in your rifle because it will hit the inside of the upper receiver. The short side sits in a slot on the bolt carrier. This slot has an opening when at the 6 o'clock position, so that when you have the carrier outside of your rifle you can turn the valve 90 degrees and easily remove it. If the valve is fully turned to the suppressed or unsuppressed settings, then it cannot fall out since the short protrusion is engaged in the slot.

The valve with intact flange:



The valve with the long side of flange at 12, short side of flange at 6, allowing installation or removal from the carrier:



And the valve set to unsuppressed - note how the short side of the flange is slightly covered up by the carrier at the corner where the "S" is located.




The long side of the flange is leaving marks in the anodizing in my upper receivers, which means the motion of the carrier or the pressures on the valve during firing are trying to turn it. I have stopped using the SBC because of my previously mentioned issues where monopodding on a magazine causes malfunctions.

Link to malfunction info?

[Slippers]

Link to malfunction info?

It's earlier in this thread. Direct link to the post: https://www.m4carbine.net/showthread...91#post2412591

[021411]

I have over 2800 rounds on my Gemtech carrier in my MK18 upper. At least 600 rounds were suppressed. I also use Gen 3 pmags and have used them as a monopod. No issues so far.

[oddballmkg]

Yes, I know the cam has a flange that hold the cam into the bolt which prevents the cam from failing out. The cam can only be removed with the with bolt removed from the rifle. But on my bolt carrier the cam is freely rotating back and forth as the gun is fired which is causing the gun switch from the suppressed mode to the un-suppressed mode. This causes the gun to either short stroke, fails to pick up another round or it fails to extract the spent round. Their has to be something that puts pressure on the cam to keep it from freely moving back and forth between the gas settings as the bolt cycles. My rifle works perfectly when the Gemtech carrier replaced with a standard BCM bolt or even the LMT enhanced bolt carrier. And I just checked my other Gemtech bolt carrier and their is tension on the cam to keep it from freely rotating.