UPDATE 7/2 - Can a Carbine Require a "Warm Up" to Function Reliably?

[Iraqgunz]

I tend to agree. I use it in my suppressed guns because with a suppressor in place it shoots smooth.

An H2 seems a little heavy for PMC bronze which is the lowest power brass cased ammo I have ever come across. I have steel cased ammo with much more punch than it has.

[vicious_cb]

When you say a Spikes H2 buffer, are you referring to their ST-T2 buffer? If so, this is not a standard H2 buffer and could be the cause of your problems.

Its also inferior to an actual H2 buffer.

[arptsprt]

Confirmed there is no o-ring around the extractor spring.

It's pretty simple. Remove the extractor and look for the black O-ring around the extractor spring. Sometimes too much extractor tension can cause issues.

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[RocketScott]

Might be a failure to eject. Check the action of the ejector in the bolt. If it's not moving smoothly it won't kick the spent case out before trying to load the new one. Could also be the extractor binding as was mentioned earlier.

It was unclear what you meant by double feed. Is the spent case getting pulled out by the bolt?

[MistWolf]

Is the spent case being left in the chamber, or is it being extracted from the chamber but not ejected? If it's being extracted but not ejected, this is a symptom of of either short stroking, or a malfunction of the ejector (or both). You need to figure out which problem you have.

Before doing anything, fire your rifle with just a single round loaded in the mag. If the rifle does not lock back on the bolt (make sure it' locking back on the bolt, not the carrier) then the rifle is short stroking and it's time to figure out why. If the problem is extraction/ejection, not short stroking, that too will be plain to see

[arptsprt]

The spent case is being left in the chamber about half way out and the bullet of the feeding round gets wedged between the stuck case and the feed ramp - if that makes sense.

I will run the diagnostics you recommend later this week.

Is the spent case being left in the chamber, or is it being extracted from the chamber but not ejected? If it's being extracted but not ejected, this is a symptom of of either short stroking, or a malfunction of the ejector (or both). You need to figure out which problem you have.

Before doing anything, fire your rifle with just a single round loaded in the mag. If the rifle does not lock back on the bolt (make sure it' locking back on the bolt, not the carrier) then the rifle is short stroking and it's time to figure out why. If the problem is extraction/ejection, not short stroking, that too will be plain to see

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[SteveL]

The spent case is being left in the chamber about half way out and the bullet of the feeding round gets wedged between the stuck case and the feed ramp - if that makes sense.

I will run the diagnostics you recommend later this week.







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If you're not able to get it resolved, take some pics of the malfunctions and post them here.

[MistWolf]

The spent case is being left in the chamber about half way out and the bullet of the feeding round gets wedged between the stuck case and the feed ramp - if that makes sense.

I will run the diagnostics you recommend later this week.

Makes perfect sense. Next question- Is the next case being pushed out of the mag at the rim by the bolt, or is the bolt pushing the next cartridge from the mag somewhere along the body of the case?

The former is an ejection problem. The latter is a sign of short stroking

[arptsprt]

Ok. Thanks. I'll look for this as well.

Makes perfect sense. Next question- Is the next case being pushed out of the mag at the rim by the bolt, or is the bolt pushing the next cartridge from the mag somewhere along the body of the case?

The former is an ejection problem. The latter is a sign of short stroking

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[arptsprt]

Ok gents...

I was able to get out and troubleshoot this today. Still having issues. Here's what I tried today:

Per MistWolf's recommendation, tried one round in mag. Bolt locked back as it was supposed too. This is definitely a Failure to Extract issue. Buffer didn't matter. I tried the Spikes ST-T2, standard H2 and H buffers. FTE with all. Tried 6-7 different mags (pmags and NHMTG GI), also didn't matter.

It was only with PMC Bronze ammo. One round fired, the bolt would lock back appropriately but the spent case would be laying loose on top of the mag. The XM193 would extract and eject every time.

I think I may have noticed a small gas leak from the key on the BCG. It is a BCM BCG. It came new with the upper. With today's round count - about 60 rounds - I have only a total of +/- 175 round through this upper and the BCG. The BCG was well lubed, and when I took it out to inspect below is what I found on one side of the key. With all the lube I had on the BCG it is clear to see what appears to be a leak. Do you think this could be enough to cause this issue?