New BCG, next round won't chamber

thegrandpoohbah

thegrandpoohbah

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So I swapped a new FA BCG into my Colt Canada IUR to replace the High Standard that it came with. It fires and ejects just fine but it will either not chamber the next round at all or it will try and the bolt mangles the round about halfway up the casing. With the old BCG it functioned flawlessly. Now, I did also install a Precision Armament M4-72 compensator at the same time as the BCG. Would that have anything to do with it? I did not have the old BCG with me today so I didn't get a chance to swap it in and see if it made any difference. Will head back to the range next weekend and give it a go. Anything else I should check?
 
Could be the difference in weight between the F/A and S/A bolt carriers. Maybe a lighter buffer is needed?
Hopefully someone with more AR know how chirps up soon!
 
What brand carrier?

Check to see that the gas key is tight.

The compensator shouldn't have made any difference in this case.

Pictures are always nice
 
since the compensator acts on gases after they have passed over the gas system it would have no impact. you could have twisted your barrel alignment when installing the compensator though

why dont you put the old bcg in to rule that out? if it doesnt work well you messed it up installing the comp, if it does work well your new bcg is crap
 
Ok, good to know the comp isn't the issue. I used a Magpul Bev Block to install it so I would be surprised if I was able to twist the barrel enough to cause a problem. I will try the old BCG next weekend and go from there. The new one is a Prime Weaponry TiN coated BCG that I got from Brownells on the recommendation of a friend.
 
What buffer weight? Was the original BC full-auto, or semi style?

If you twisted the barrel in the extension, your gas tube will be cocked up. If it's straight, your barrel is fine.
 
Sounds like it's short stroking, a lighter buffer may be all it needs.
If your gas key is tight and sliding over the gas tube smoothly try putting a single round in the magazine and fire it, check to see if it locks back on the bolt face, front of the carrier or not at all.
What buffer is in it? Standard carbine or something heavier? You can try taking the buffer apart and removing one of the weights and trying it again if everything else seems to be working fine.
 
willywonka519 said:
I had the same issue when trying to run a FA BCG in my IUR. The CC one that came with my SA20 worked, as did a Stag Arms semi-auto.
Click to expand...

If you used an in spec fa bcg and it didn't work on the iur that means the iur is out of spec, they were danish contract overruns, unless they were the sas uppers regardless both are issued with fa bcg.
 
I suspect that a standard carbine or a H buffer will probably solve your problem. Just out of curiosity are you using cheap under powered ammo like Barnal or something? If so try some 5.56 in it and see if that works.

A break in period shooting some 5.56 may allow the cheap stuff to run after a while without changing the buffer. Good luck.
 
I have found some bcg's need to be broken in with higher pressure ammo. My old lmt did and a ds arms bcg took a while to run reliably on a 18 inch rifle lenght upper.
 
I will try swapping the BCG first to see if that is the problem. From there I will get my hands on a new buffer and try that with the new BCG. The ammo used yesterday was Federal XM193 which has never given me problems before.
 
Found standard and H buffers at a reasonable price so I've got them ordered. Hopefully that is all that is needed to run the new BCG. I will report back once I have a chance to troubleshoot some more.
 
Ok, tried the factory BCG today and it ran flawlessly as usual. Tried the new BCG and it was better but still had a few hiccups. So I didn't bugger the gas tube when I installed the brake. I will try the H buffer once it arrives and see if that solves the problem.
 
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