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

[arptsprt]

UPDATE POST #38

Sounds like a stupid question I know, but I have been having some issues with my BCM 12.5 KINO with PMC Bronze ammo. Let me preface this thread by saying this is NOT a "I think something is wrong with my BCM upper" issue.

First my set-up:

DD SBR Lower (new)
BCM 12.5 KINO Upper (non BFH) unsuppressed (new)
BCM BCG (new)
BCM Mod 4 CH
Spikes ST-T2 buffer/OEM spring

Here is (was?) the issue:

Numerous double feeds. Double feed as in an empty and a live round caught in upper.

My guess is that the malfs were being caused by short stroking likely as a result of weak .223 PMC Bronze ammo and the H2 buffer. The carbine functions 100% with good 5.56 milspec ammo.

The set-up is relatively new. I had only put about 30 rounds down the pipe for initial zero and function tests. All slow fire.

I initially I had numerous double feeds (as defined above) with the PMC ammo when the gun was cold - maybe 2 rounds down the pipe before the double feed. Switched over to 5.56 and was good to go. Shot about 120 rounds of 5.56 doing various rapid fire drills - no issues. Tried the .223 PMC again (another 40 rounds) and it ran just fine.

To the point with my question(s): can a gun function more reliably when warm vs when cold? And, could this be a "break-in" issue - is there such thing with an AR? Anyway, this is a new one to me. I really think that if I had had the H buffer in to begin with I would not have had the issue with the .223 when cold. I do not intend to be satisfied with "it works okay when it's warm" and I'll play around with it later in the week, mainly by trying the H buffer.

Thanks for the input.

[Iraqgunz]

You didn't have double feeds. You had a failure to extract that created a failure to feed. Do you have an O-ring on you extractor spring?

[arptsprt]

Ok. Thanks. My bad. I used the definition of "double feed" from an old thread I read about double feeds - this was the definition from Robb Jensen - M4C.net staff.

Anyway, regarding the o-ring, I do not know. It was a new BCM BCG that I ordered with the upper so I ass-u-me no since they usually don't ship with the o-ring. I will have to verify this.

You didn't have double feeds. You had a failure to extract that created a failure to feed. Do you have an O-ring on you extractor spring?

[Jwknutson17]

I would run it for a few hundred more of 5.56 through it, before I would start looking hard at issues. When you have a spent casing still in the chamber, it failed to extract and the new round is unable to feed for obvious reasons. While it might seem its a double feed, your true issue is failure to extract.

If you have a standard H2 or even an H1, I would run that over the spikes from now on, especially if chasing down issues.

[SteveL]

Sounds like a stupid question I know, but I have been having some issues with my BCM 12.5 KINO with PMC Bronze ammo. Let me preface this thread by saying this is NOT a "I think something is wrong with my BCM upper" issue.

First my set-up:

DD SBR Lower (new)
BCM 12.5 KINO Upper (non BFH) unsuppressed (new)
BCM BCG (new)
BCM Mod 4 CH
Spikes H2 buffer/OEM spring

Here is (was?) the issue:

Numerous double feeds. Double feed as in an empty and a live round caught in upper.

My guess is that the malfs were being caused by short stroking likely as a result of weak .223 PMC Bronze ammo and the H2 buffer. The carbine functions 100% with good 5.56 milspec ammo.

The set-up is relatively new. I had only put about 30 rounds down the pipe for initial zero and function tests. All slow fire.

I initially I had numerous double feeds (as defined above) with the PMC ammo when the gun was cold - maybe 2 rounds down the pipe before the double feed. Switched over to 5.56 and was good to go. Shot about 120 rounds of 5.56 doing various rapid fire drills - no issues. Tried the .223 PMC again (another 40 rounds) and it ran just fine.

To the point with my question(s): can a gun function more reliably when warm vs when cold? And, could this be a "break-in" issue - is there such thing with an AR? Anyway, this is a new one to me. I really think that if I had had the H buffer in to begin with I would not have had the issue with the .223 when cold. I do not intend to be satisfied with "it works okay when it's warm" and I'll play around with it later in the week, mainly by trying the H buffer.

Thanks for the input.

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.

[arptsprt]

Yes, it is the ST-T2. Somebody gave it to me so I thought I would try it. My 11.5 BCM upper has a standard H2 buffer and eats everything so you might be right.

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.

[Iraqgunz]

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.

Ok. Thanks. My bad. I used the definition of "double feed" from an old thread I read about double feeds - this was the definition from Robb Jensen - M4C.net staff.

Anyway, regarding the o-ring, I do not know. It was a new BCM BCG that I ordered with the upper so I ass-u-me no since they usually don't ship with the o-ring. I will have to verify this.

[firefighter37]

Not 100% sure its the cause or not, but like SteveL said I would ditch that Spikes buffer. I don't run anything from Spikes personally.

[TMS951]

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.

[arptsprt]

Come on IG gimme some credit... My post may make me seem like I'm clueless regarding all things AR, but I am not that bad... When I cleaned and inspected the BCG when I first got it, I was simply too lazy to remove the extractor to inspect to that detail. I will do that tonight.

As usual, thanks for the input gents.

Chris

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.