atxhoghunter

Haven't compared the two JP products, but did not notice any unpleasantness while firing. The .308/.725 Recoil Eliminator that I needed is only available from the manufacturer. Midway/Brownells don't carry it.

As for the Recoil Eliminator and "concussion" ... It is the most effective muzzle brake I have ever used. Have one on a 7mm STW and it tames it quite nicely. The sound was no more than usual for the shooter. However ... if you are to either side of the shooter ... you will be miserable. Maybe not a concussion, but tinnitus is a big possibility. It is loud. Could have just been the way things worked, but the 9 other stalls at the indoor range were empty by the time I finished by 40 rounds.

DMPS Complete Upper from Midway USA. 80% lower. Simmons Scope. Battle Gray Duracoat. Recoil Eliminator from JP Industries. Ace Skeleton Stock. Hogue handguard with rubberized grip. ERGO rubberized grip (matches nicely/feels great with the Hogue handguard).

A thorough cleaning, a new brand of lubricant, and the discovery/sanding of a rough spot inside the upper receiver and my .308 now will strip and fire from a fully loaded magazine. Found a very limited amount of "dirt" duirng the cleaning. Not more than you'd expect from firing 40 factory rounds. Changed from the lubricant that's seen me through a half dozen mauser builds (Rem Oil in the spray pump) to the incredibly slick FP-10 from Shooter's Choice. That seemed to make the biggest difference. Did find a mysterious rough area inside the upper receiver (where the bolt travels) that knocked-down with some brushing. Still not completely gone. Can't really see it, but can feel it. Hoping its a foreign body and not an area where the upper was poorly manufactured. Thanks for everyone's help.

No reloads fired to date. Forty rounds of factory Hornady Match ammo is all that's gone down the pipe. Will weigh the buffer tonight.

Learned years ago during my SKS stage to let the bolt slam home. Definitely doing it now that I'm in my AR phase. In an attempt to summarize more clearly ... the rifle functions flawlessly (in every way) as long as I don't have more than 3 rounds in the magazine. It locks open on the last round, shoots sub MOA, strips, feeds, fires and ejects. Will clean and lube tonight and hope for a kitchen-pass to the range early one morning this weekend.

Thank you for the good responses. Hopefully it is a lube and break-in issue. Will tinker with it as time allows. As for the lower being in-spec ... according to my micrometer it is. I butchered a .223 lower a few months ago as a warm-up. Learned from that. Interesting no one espouses the small based dies.

Yesterday was my first test-fire of a DPMS LR-308 build. Upper came complete from DPMS/MidwayUSA. Lower is an 80% I finished myself. Rifle is extremely accurate. Fired 40 rounds. Followed break-in/cleaning procedures. Last three rounds were sub MOA at 100 yards. Love it. Issue #1: If I put more than three rounds in any of my magazines (DPMS metal 20 round, Magpul 10 round, Magpul 20 round), the bolt has trouble stripping the round when you attempt to manually cycle with the handle, The result is the bolt only closes about 95% of the way. The bolt is then extremely difficult to pull open/eject the poorly seated round. Makes no diffence if you insert the magazine when the bolt is open or closed. The barrel is carbine length with a DPMS .308 carbine buffer spring and carbine buffer. More perplexing is that when testing with .308 SnapCaps, of which I have ten, there are no failures to strip/feed. Keep in mind this is all happening prior to firing the gun. No gas issues. This issues is specifically stripping the round from the magazine and seating it properly when the magazine is under pressure with 4 or more rounds. Issue #2: After returning from the range I mocked-up 20 rounds of ammo (no powder or primer) with Sierra Gamekings with a COL of 2.7" (midway between the 2.8" Hornady Match ammo I test fired, and the 2.55" SnapCaps). Used Gamekings because their shiny/single-metal surface would show if/where the bullets might be hitting the ramp or rifling. A noticeable mark is being left on each bullet when the rifle is being cycled manually. Starts near the tip of the bullet and twists down half the length of the ogive, decreasing in depth as it goes, then disappears. Seems to me that means its catching on the rifling somewhere. The brass is undamaged. I did notice that the 10 SnapCaps also have some nicks on their bullet sections, but have fed flawlessly. Here are my possible fixes. Please add or redirect when you see something that won't work. Clean and Lubricate: Sure seems like I did all that, but maybe with its first firing some hidden fabrication grit broke loose. Polish M4 Feed Ramps: I know some folks say this doesnt help, but it might work. Extra Power carbine buffer spring: Have one on order from Sprinco. Will be good to have as a spare, even it that's not the fix. Purchase and use a .308 small base die set.