Revelation

Finally received the upper back from the gunsmith today. Headspacing is correct and rifle is ready to go. I had a chance to take it out and put about 20rds through it. I will put more through and take pictures soon. Here are the details from this short session: Now using a 5.5oz CAR-10 heavy buffer and their carbine spring as well to match. SLR gas block set on 10 out of 15 (tried settings 5-13) but setting 10 on gas block is letting the rifle cycle rounds perfectly thus far, spent brass looking good. Brass ejecting anywhere from 2-4 oclock but mainly around 4 oclock. HERE IS THE ONLY ISSUE THAT IM SEEING STILL. Bolt will not lock back on last round, no matter what. Doesnt matter what gas setting, whether I am lubed to the max or running a little more dry, what ammo I'm using, tried multiple bolt catches, it doesnt matter. It won't lock back lol. But it does cycle rounds perfectly. I'm stumped, but am ready to either leave it the way it is or sell it and buy a bolt gun. Like I said, I can take pictures and run more rounds through it the next time I'm able to get out, just request if you think you may have an idea what could be wrong. Thanks

I will update this thread when the gunsmith gets the upper back to me. Its amazing what covid has done to wait times in the gun world. I got lucky at 3 weeks wait time when some other local gunsmiths were a year out on work!!

This leads me to one more question, the bolt wouldn't close on the "go" gauge, not the other way around, so wouldn't the chamber be opposite from oversized and with a little help if they got the bolt to close on the go gauge we should be good to go?

Thanksfor the explanation. I originally used the Faxon BCG when I was having the problems, which then I returned it and the buffer, gas block, and other parts because they weren't as nice as I expected. I picked an Aero Precision NB BCG (looks and feels to be 5x the quality of the faxon) and according to Faxon barrels, this is one of their recommended BCG's for their barrels. I have not shot at all with it yet and got the headspacing checked. That is my current situation. I will see what the gunsmith says about the situation and otherwise will try to contact Faxon.

A gunsmith can't?

Update: Received the new parts. Went with the Slash CAR-10 buffer system as well. Will post more on the new parts with plenty of pictures later. We have a problem though. Had headspacing checked by a reputable shop, it was a no-go. They currently have the upper and are going to space it correctly. Will update as soon as possible so this thread isn't open-ended!

I have tested both manually, they both sit in exactly the same spot on the follower whether they are engaged or depressed. No difference there. The S7 sticks up slightly further which you can sort of see in the two pictures, but its overall mass is less. When I receive the rest of my parts and initiate testing and take additional pictures, I will try both again. Thanks again!

While we are waiting on parts.... WHICH bolt catch? They are both advertised as .308 catches. One came with my Tom's Tactical AR-10/LR-308 lower parts kit (the beefy one) and the other is a V Seven Weapons S7 LR308 catch. Any difference to be had here except for possible shear resistance? It does look like the S7 catch sticks up a tad bit further when the mag is in. Thanks boys! Excited to start sending freedom bits downrange.

I'm not sure where any of you got that I'm butt hurt from? Maybe you were talking to the general audience though. Just my attempt at being respectful to edgecrusher. I appreciate the help very much actually and I only enjoy singling out junk parts if they are junk. Anyways, that really helps so I will take a gander at a more original setup to start with and also take a look at Slash. Will report back later.

Thank you, will do!

edgecrusher: I want to clarify.. you think the hyd buffer and spring ARENT enough to slow it down? When I pull the charging handle with this setup, it is STIFF. Probably 3x stiffer than my average AR-15. I thought it would be too much, not too little. I would love to keep this buffer, but you may think I need something heavier. Easy fix maybe heavier Sprinco brand or similar spring instead of replacing the pricey buffer itself? Also, not questioning your knowledge dont take me wrong, but this same Kynshot buffer and JP spring are the ones recommended to mate together for a regular carbine adjustable stock like im running. Could it be this far off still? Just provoking thought, don't think I'm questioning you on everything. I could use some more lube most definitely. I will do all those things listed this next time around, might be a couple weeks the way things are shipping currently. I appreciate the help!

I realize similar threads have been created, I've read through 3+ dozen to no avail. Any help much appreciated. DPMS LR308: Aero M5E1 enhanced upper Aero M5 lower Faxon .308 18" 1/10 barrel .750 rifle length Faxon .308 BCG Aero melonite gas tube rifle length JP .750 adjustable gas block VG6 muzzle brake PMAG's Using a normal Aero 7" carbine adjustable buffer tube paired with Kynshot 2.5" Hydraulic .308 buffer and JP tuned and polished .308 CARBINE LENGTH buffer spring AMMO: Federal Gold SMK 175 grain (Factory) SO: Yes, I can manually pull the charging handle and the bolt will come back and it clears the bolt catch by about 1/4" inch just fine. Manually, it easily catches back and functions fine in every way that I can tell. The JP gas block can go to about 7 turns out which is maxed, they suggest starting at 2 turns out and going a half turn with each shot to adjust. I have tried every setting from 1 turn out which will not push the bolt back at all (single shot), to 7 turns out which acts way over-gassed brass-wise (tears up brass, shells come out hotter than a cat on fire, excessive primer cratering possibly?) and the bolt gets halfway stuck on the mag. I couldn't tell if it was still not going far enough back or if it was going too far back too fast and catching halfway and sticking on the empty mag. Either way, the bolt head never caught on the actual bolt catch properly when testing the single round lock-back; I am stumped. MY NEXT STEPS: I have returned the Faxon BCG and JP gas block just incase, I am going with an Aero Nickel Boron BCG, SLR sentry 7 adjustable gas block and I will have the head-spacing checked this time before I install the new parts. (I had not before, didn't know it was a thing) I also ordered a regular .308 carbine buffer spring and new gas tube as extra options just incase. Pictured is the .308 buffer and spring I am running on the right side vs just my normal AR-15 buffer and spring on the left. Sorry if this is too much info or not enough at the same time. I have built many AR-15's successfully, the .308 world is new to me. Thank you.