It could be the gas key is not properly staked into place. See if it moves. My 308 build had the same symptoms you described.
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It could be the gas key is not properly staked into place. See if it moves. My 308 build had the same symptoms you described.
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Replace the extractor spring with a Colt copper colored extractor spring. It's made to give the proper tension to an M4 extractor without using an O-ring. I believe it still uses the insert but you'll have to check
INSIDE PLAN OF BOX
- ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
- MATCH SCRATCHES ON MATCH-BOX
- MATCH LIGHTS FUSE TO TNT
- BOOM!
- HA-HA!!
-WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"
I am American
I think it would work the opposite way - the unsuppressed subs wouldn't generate as much power, so if it cycled okay with subsonic with the 1 or 2 buffer, I would be inclined to think that a heavier buffer would slow down things for the full power rounds.
Those pistol systems are pretty abrupt, my pistols all have carbine systems for that reason, of course you can't go as short on the barrel.
Last edited by 26 Inf; 10-07-15 at 17:14.
4.6oz H2 buffer and standard carbine spring is recommended by AAC for proper operation of the system with pistol gas.
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In my experience, it's pointless to try different buffers, springs, mags etc. until the extraction issues are resolved
INSIDE PLAN OF BOX
- ROAD-RUNNER LIFTS GLASS OF WATER- PULLING UP MATCH
- MATCH SCRATCHES ON MATCH-BOX
- MATCH LIGHTS FUSE TO TNT
- BOOM!
- HA-HA!!
-WILE E. COYOTE, AUTHOR OF "EVERYTHING I NEEDED TO KNOW IN LIFE, I LEARNED FROM GOLDBERG & MURPHY"
I am American
Well I got the BCM extractor upgrade today. I installed the spring with the insert and headed to the range. I tried both types of ammo and still would not extract. So I took the bolt apart and added the o-ring. What do you know...100% reliable extraction. I put about 50 rounds through (a mix of both ammo) and the gun was flawless. I know some people have said that you should not have to rely on the o-ring but I wonder if it is something with the 300blk round and pistol length gas that many rifles need it. It sounds like AAC puts them on their BCG's for 300blk rifles and BCM has a note on their site stating that customers should use the o-ring with their 300 barrels. Gun was a pleasure to shoot. Blast was not bad at all even with the Efab brake. I was noticing the blast from my 16" AR 5.56 with the Lantac Dragon a lot more. For now I am thinking the issue is solved. At least its extracting/ejecting now. I was by myself so I am not sure on the ejection pattern but it seemed to be between 3 and 4 o'clock. Cases had the flattened spots on the neck...assuming they are hitting the deflector.
Have to say that BCM was great. They must have caught part of an earlier order that I submitted before it left the warehouse and included the springs with it. I was expecting them tomorrow at the earliest...definitely not today! Also, Ballistic Advantage was awesome. Clint was more than willing to help me out. I let him know that it works with the o-ring and he said that his offer still stands. If the issue comes back that I should send the upper to him right away. Of course thanks to everyone here that chimed in offering suggestions as well.
I agree in principle, but how else do you solve extraction issues when you believe the weapon is over gassed? Sure you check the carrier key, gas rings on the bolt, back of bolt lugs, and extractor. When all that checks out and it still isn't extracting AND the person tells you that the cases that initially wouldn't extract, will extract when 'cold' and placed into the chamber, one valid thought is that something is trying to extract the round before it contracts after the pressure drops:
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.
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.
Now, I agree that the missing 'o' ring jumps out, and indeed it works with the 'o' ring installed, but I tend to agree, I'd like my rifle to function without the 'o' ring. I doubt the extractor springs on both bolts were sacked, so I would look to spring or buffer to make this thing pause a millisecond before extraction begins.
JMO
I agree with you. My next step is to pull another tungsten weight from a spare buffer and add it to my A5 buffer which will effectively make it an A5H3. Its was just nice to be able to load up and run through a whole mag today. Got tired of this single shot business. LOL
If anything this experience of building a 300blk has encouraged me to increase my working knowledge of the whole AR platform. I have built 5.56's before but they ran fine from day one so I didn't have to put too much thought into it. Pretty much Lego's for adults. Initially I thought that if I were to have extraction issues it would be intermittent failures not 100%. But it seems at least in this case there was a definitive line between 100% failure and 100% reliable. There were no marginal improvements as I made changes. It will be interesting to see if a heavier buffer will allow me to rely just on the heavier extractor spring.
Another thing I have learned is that I need to move out to the country so I can tweak things and then shoot off my back porch to test the changes instead of running to the range.
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