So I have completed a 300blk build. I took it to the range and I am having extraction issues. I have tried a couple of things to troubleshoot but all combos have resulted with the exact same result. I load 1 round in a mag, seat the mag and release the bolt, pull the trigger and the gun fires, bolt locks back, spent casing is left in the chamber. If I let the bolt forward gently and push it home with the forward assist then pull back the charging handle the spent case comes out pretty easily. Also if I load a round then pull back the charging handle without firing it the round comes out as easy as you would expect it to.
So far I have tried the following variations with 2 types of ammo (Fiocchi 150gr FMJ, Remington 125gr Match):
2 different BCG's: Wilson Combat 5.56 NP3 and a LaRue 5.56 BCG
2 buffer weights: A5H1 and A5H2 - bolt locked back every time for both buffers
Additional setup info: Ballistic Advantage 8.3" 300blk barrel, BCM intermediate A5 buffer tube w/Sprinco green spring, BCM Blem upper, EFAB muzzle brake, no suppressor and no subsonic ammo has been used.
Looking at the spent casings I not see any gouges from the extractors nor do I see brass shavings on either bolt face. Any other trouble shooting ideas? Neither extractor has a crane o ring and I would prefer to get the rifle working without one.
I have contacted Clint with BA and he is helping me but I figured that I would also check here and see if anyone else has had similar issues and how they fixed it.
***Fixed - Gun Running great***
I got the barrel back from Ballistic Advantage. They ran my barrel with my bolt and a few other bolts in the shop. They said it ran fine for them but decided to send me a new barrel. I have installed the new barrel and made it to the range today. Everything ran great with the A5H2 weight buffer and the crane o-ring on the extractor spring. No marks on the brass at all. For kicks I disassembled the bolt and removed the o-ring. That caused failure to ejects with the spent case laying loose on top of the magazine. So coupling that with the fact that BCM recommends using the o-ring on their site for 300blk and AAC sending their bolts out with the o-ring I guess it is not unusual to need them. I may try to increase the weight of the buffer and see what happens as the bolt locked back every time on an empty mag. Beyond that I am calling it good to go. As far as ejection of the brass they were bouncing off the stall divider and piling up right by my feet.
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