FTE and other problems with 7.5" SBR New build, Please Help
I have a new build SBR with a few problems.
First of all the Specs.
JD Machine AR15 Pistol SBR Upper Receiver 5.56 7" This upper includes a JD Machine Upper Receiver, 7" Citadel 1/7 twist Chromolly Heavy Barrel, JD Low-profile Gas Block, Expansion Chamber Compensator, FSI Free Floating 7" Quad Rail Handguard and Charging Handle.
Fail Zero bolt and carrier group complete kit
Grizzly stripped lower
Timney AR15 3lb trigger
DPMS Lower Parts Kit minus trigger
misc other stuff that shouldn't pertain to the problem.
Now the problems.
1. With the Fail Zero BCG it only barely holds the bolt back when the charge handle is pulled and the bolt catch engaged. I can barely bump the gun's stock and it will release the bolt. I changed the BCG to the stock one from my S&W M&P15 and the problem disappears.
2. With both the Fail Zero BCG and the M&P BCG I can only get two or three max shots at a time before I will have a FTE. Most often a stovepipe sometimes the spent casing won't fully extract before the new round tries to go in and gets doubled up in the chamber. I pulled out several new rounds where the projectile was shoved back in the casing because the spent casing was not extracted. I tried several different magazines both Pmag and a few different steel ones (colt and the one from my S&W included) with the same results. The ammo was a mix of Federal 55 Grain FMJ and PMC Bronze 55 Grain FMJ.
Thanks in advance.
It would help if we knew what buffer you are using. you may need a heavier one or a lighter one depending on your gas system.
Standard buffer I've got a few buffers that a friend of mine has left over from his builds, how would I tell them apart? Weight?
Most are marked in some manner, if not, a kitchen scale will tell you which is which.
I had the same extraction problems. First, if the buffer is not marked it is a standard buffer, otherwise it will have an "H","H2", "H3", etc. on the end.
I used a spikes ST2 tungsten buffer on my SBR and it works great. BCM Linky to ST2 for $29.99
While you are at BCM pick up an extractor upgrade kit here: Linky to Extractor Upgrade Kit $4.95
Buy a few of the extractor kits because they are good to have and the shipping will justify getting at least 3 or 4 with your order. I use them on ALL of my AR pattern rifles.
This should fix your extraction problem. I have no idea what could be up with your BCG.
Please give us an AAR.
Thank you very much guys, I'll get my order in and check back as soon as I get back to the range.
Thanks again for posting a solution. I had the EXACT same problem with my 7.5" SBR with a JD Machine upper and a Del-Ton lower. I ordered the parts suggested to see how it works out.
I used a H3 in the Noveske 7.5" Dimplomat and it functioned 100%..The buffer is definitely the first things I would swap to try and resolve the issue.
This is for the Failure To Eject (FTE) only issue:
Do you have the O-Ring installed on the extractor for both bolts? I just looked up the fail zero info and they don't use one, so that's a big no.
About a year ago, I changed my upper to a 10.3" barrel from a 14.5" and a new complete Bolt Carrier Group from BCM, I didn't install the O-Ring that came with the bolt. I had failure to ejects or stove piping issues like you do, installed the O-Ring and over 3K rounds later no FTE
So I suggest getting the BCM Extractor Spring Upgrade Kit
Try a lighter buffer spring. My buddy converted his RRA from a 16" to a 10.5" and had FTE issues. He swapped out the spring and was GTG. If that does not work than you can look at swapping out the buffer. **original upper was a mid length gas system and the new one was a carbine.
Hope you get it worked out.