Help with ugly FTE

[t15]

Hello, I've got a BCM 11.5 that was giving me FTE's almost every shot. Looked just like this every time;
doublefeed.jpg

I originally had a used DD BCG in the gun with an H2 and new carbine spring, less than 100 in this configuration, but no problems. Today, I go to the range with an unfired BCM BCG and was getting these FTE's like crazy!

Ammo was Independence for the first two mags and then switched to PMC Bronze, no difference made.

Thought I over lubed it, so I stripped it down and wiped it practically dry and really spent a lot of time getting on the bolt face and under the extractor. No difference made.

Swapped the 11.5's bolt into a BCM 16 mid-length and H buffer, ran 100% with same magazine and the Independence.

Put the 16's BCG into the 11.5, ran 100% and ripped through 20 rounds of Independence and 20 more of PMC. When I put the bolts back to their original rifles, the 11.5 wouldn't cycle!



Any help, tips, or wild speculation is appreciated. Thanks!

[TacMedic556]

How does the extractor look? Damaged at all? Sounds like is ran fine and shouldn't be damaged, based on the 16" handling it fine.

Proper insert and spring? If the extractor is intact and you have a black insert, try a 5 coil extractor spring and shoot with the same ammunition and magazine. See if that changes performance at all. That shorter platform has more pressure as you know, less dwell time and so on. I put sprinco 5 coil extractor springs in my SBRs. No issues on all ammunition. Hope it helps. Keep us posted.

[t15]

Thanks for the reply, I have not removed the extractor to look at what combo BCM shipped it with. I do have a 5 coil sprinco I could try, but this BCG and the one out of the 16 were purchased very close together both from BCM's free BCG deal. I am assuming they both have same setup, but the 16 is my friends rifle so I can't confirm right now.

I did have at least 2 stuck in the chamber that required butt on the bench and both hands on the charging handle.

I will run a bore brush and rip cord before the next trip. I will also install the 5 coil and only use xm193 all from the same batch, but could the 11.5 have a tight bore if it works great with 2 other bolts??

edit: extractor looks normal. Brass marks, but no missing material and tension seemed to be what I'm used to.

[26 Inf]

I'm guessing you just swapped BCG's and not just the bolts.

Swap the bolts into the other BCG and see if the malfunctions still occur. Think about this and see if it makes any sense - FTE's are sometimes caused by the weapon beginning to cycle before the case has contracted after firing - over gassed. If one bolt doesn't seal as tight in the BCG (worn gas rings) then it might let the weapon function because of a slight delay/less abruptness in cycling. So my theory is the new BCG is tighter and that combination, combined with the shorter gas system on the 11.5 is causing the FTE's.

Also check the carrier keys to see if you have any signs of gas leakage - 'v' shaped carbons jets.

Hey it's one o'clock, the only reason I'm up is because my daughters completely hosed up the tub and toilet in their bathroom. Girls.

[MistWolf]

Judging from your photo, you're getting a double feed. The primer of the top round has not been struck which means it's still live. A double feed is a mag problem

[Sticks]

The pic is even labeled "Double Feed"

Did you post the right pic?

[Iraqgunz]

Exactly.

Judging from your photo, you're getting a double feed. The primer of the top round has not been struck which means it's still live. A double feed is a mag problem

[SkipD]

Hello, I've got a BCM 11.5 that was giving me FTE's almost every shot. Looked just like this every time;
doublefeed.jpg

My first question is about the attached photo. Was that photo actually taken by the OP or was the photo borrowed from somewhere else because it "looked like" the OP's problem?

[t15]

Judging from your photo, you're getting a double feed. The primer of the top round has not been struck which means it's still live. A double feed is a mag problem

Sorry, not my photo. In my situation, the round half in chamber is already fired. The malfunction does otherwise look exactly like this photo except for the primer.

When I remove the magazine, usually the hot round will fall out on it's own and the fired case will be left hanging half way out of the chamber loose.

[t15]

I'm guessing you just swapped BCG's and not just the bolts.

Swap the bolts into the other BCG and see if the malfunctions still occur. Think about this and see if it makes any sense - FTE's are sometimes caused by the weapon beginning to cycle before the case has contracted after firing - over gassed. If one bolt doesn't seal as tight in the BCG (worn gas rings) then it might let the weapon function because of a slight delay/less abruptness in cycling. So my theory is the new BCG is tighter and that combination, combined with the shorter gas system on the 11.5 is causing the FTE's.

Also check the carrier keys to see if you have any signs of gas leakage - 'v' shaped carbons jets.

Hey it's one o'clock, the only reason I'm up is because my daughters completely hosed up the tub and toilet in their bathroom. Girls.

Thank you, I think I'm following. Yes, I was only swapping complete BCG's. Would a heavier buffer make a difference if this was what is happening? Sorry about your bathroom, I hope they told you about it immediately. It's always nice when they clog it up and then go back to bed!