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Ok, so this amazes me. I am not doubting your experience, but I am at a total loss as to why this could be.
If the bolt caused extraction/ejection issues ok, these short guns could need the extra extractor tension.
The idea that a bolt will effect the length and speed that the carrier travels is pretty wild to me.
Does any one have an idea as to what could going on?
Last edited by C4IGrant; 07-05-11 at 10:18.
Alright guys, good news.
A friend of mine who's taken on the project has built his own semi-dedicated suppressed upper with the gas port size I'm using. Here are the specs on his gun:
Upper receiver: VLTOR MUR without bolt assist.
Charging Handle: Noveske Gunfighter
Rear Sight: KAC Micro 300m
Front sight: KAC M4 flip up front sight
Gas block: KAC Mk. 12 spare that I had
Barrel: BCM 20'' rifle length barrel, cut down to 11.3'' + .056'' GP size
Bolt carrier: LMT Enhanced Full Auto carrier
Bolt: BCM + 5 coil extractor spring + O-ring
Lower: LMT + KAC ambi magazine release + LMT ambi safety
Stock/Pistol Grip: LMT Standard M4 stock + M16A1 pistol Grip + Magpul trigger guard
Trigger: LMT 2 stage
Suppressor mount + Suppressor: Surefire brake + Surefire full size can.
Rail: VLTOR CAS-V Mid
Buffer: VLTOR A5H3 (5.1 oz.)
Action Spring: Colt USGI M16A2
Receiver extension: VLTOR A5
Here's the important part:
The gun DID function with the BCM bolt with both a stronger extractor spring AND O-Ring, but experienced failures to extract, and I think eject with the LMT Enhanced Bolt (which he owns as well, but is to be used on another rifle - 14.5'' carbine).
At some point we're going to measure the spring tension (in pounds) and compare the two, but to me just by finger pressure it seemed like the BCM bolt with the bolt upgrade kit was stiffer, and provided stronger extraction. (Suppressed, the LMT bolt couldn't extract at all unsuppressed.)
Also, with the VLTOR A5 the bolt will lock back on his gun as well, I think we've determined it's repeatable. But he isn't using a SpringCo GREEN spring like I am, and we didn't shoot it on my lower.
Ammo was 475 rounds of 62 gr. Lake City M855 FMJ.
tl;dr: BCM Bolt + Upgrade kit = success, LMT Enhanced bolt = phail.
We miss you, AC.
We miss you, ToddG.
I would like to add my take on the enhanced bolt.
Per Bill Alexanders description of the bolt. It was never designed to go into a SBR, other than a 14.5'' barrel in conjunction with the enhanced carrier, the enhanced carrier is what allows it to work in a 14.5'' SBR with the extractor tension LMT chose too use with that bolt.
In all other configuration middies and rifle length it should work fine.
I know that MSTN has used the enhanced bolt in allot of there builds the ones that I have seen have been in middies and rifle lengths.
It would seem like a simple solution would be for somebody to offer increased tension extractor springs for use in SBR's , but maybe there is something I am unaware of why one has not been offered.
...THIS is exactly what I was going to post to ask about. I'm thinking I'll have to pick LMT's brains in a phone call to ask if this would work.
I reread the Surefire Mini and AAC Mini4 threads and it reminded me how much I wanted to make a dedicated suppressed SBR. As a guy with very few tools, what are you guys using to open up gas ports? The barrels I'll be getting will be LW 50s from Lothar Walther themselves, and I don't think I'll have any trouble convincing them to start at a small .055 and working my way up from there on my own.
-B
RIP, Jeff Dorr: 1964 - July 17, 2009
"When young men seek to be like you, when lazy men resent you, when powerful men look over their shoulder at you, when cowardly men plot behind your back, when corrupt men wish you were gone and evil men want you dead . . . Only then will you have done your share." - Phil Messina
I have a 14.5 carbine upper. Will the LMT carrier help bleed some gas to help it shoot smoother. I have an h2 buffer but standard A2 hider on it. It shoots fine but the carbine system is a little bit harder than my middy. I'm not recoil sensitive, my middy has just spolied me I guess as to how smooth it runs and how little recoil if has, I want to try to get this carbine system to run as smooth. I figured the LMT enhanced carrier might help that since it bleeds off a little extra gas.
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