Bruce

Final update - I polished the barrel chamber with Flitz, not to a mirror finish but enough to make it noticeably shiny. Added the Sprinco orange buffer spring along with the HeavyBuffers CAR-10 2.5”, 5.6oz buffer. Opened up the Superlative Arms adjustable gas block, ran 20 rounds of Sig 55 grain Varmint & Predator through it and......................it WORKS!! I ended up closing the gas block 1/2 turn to get a very nice 3 o-clock ejection pattern and my brass doesn't even touch the brass deflector. No shoulder dents, no bent rims and no sooty brass. Last round BHO every time with MAGPUL mags. Thank you so much to everyone that commented on this project especially @98Z5V !! I can honestly say that I would NOT have ever figured this out without your help.

Brief update - Testing on this build has been delayed by an injury to my right hand. I expect to resume by the week of July 26th.

@98Z5V I came here for sound advice and knowledge and everything said so far makes perfect sense. I'll polish the chamber, add the Sprinco orange spring along with the 5.6 oz buffer and fully open up the gas block. Next testing session is about 2-weeks away. Thanks again everyone.

Thanks. The Sprinco orange spring arrived today and I have a #44 (.086) bit and #42 (.0935) bit on the way. Keeping my fingers crossed.

I will try this before any further testing. Thanks.

Thanks, Yes, tried Nosler 95 grain partitions over H4895 and didn't really see any difference. But that was before I got the CAR-10 heavy buffer so..........

Yeah, I'm still living here but I spend lots of time with my friends in WI. 🙂

Hello everyone, I've been around firearms pretty much my entire life. Growing up on a farm in SE Minnesota gave me ample time and opportunity for target practice, hunting and tinkering. I hope to become a contributing member of this group while learning from the vast knowledge of you established members.

Hello everyone, First, I have built two LR-308 carbine projects and two AR-47 carbine projects with no issues at all. But I have an LR-243 build that has stubborn cycling issues. Before we get into that, here are the build specifics as they stand today: Polymer80 Warrhogg 308 Lower DPMS LR-308 Lower Parts Kit AR-15 Carbine Lower Receiver Extension (7” inside depth) HeavyBuffers CAR-10 2.5”, 5.6oz Buffer DPMS 308 Carbine Buffer Spring, P/N F1000588 10-7/8” OAL, 29 Coils, .073” Wire AR Stoner 22” AR-10 .243 Win 1:10 Barrel w/.080” Rifle Length Gas Port Superlative Arms .936 Adjustable Gas Block AR-10 Rifle Length Gas Tube 15-1/2” OAL Aero Precision DPMS 308 Upper Brownell's LR-308 Bolt Carrier Group Ammunition: Federal 55 grain Varmint & Preditor Symptoms: With a non-adjustable gas block and 2.5”, 3.8 oz buffer the system is so severely over gassed and improperly timed that it tears the rims off of the brass and it has to be tapped out of the chamber with a cleaning rod. Adding the SA adjustable gas block opened 2 full turns (8 clicks) allows for extraction at 3:00 but no bolt hold open. Opening the gas an additional click (9 clicks) allows for extraction at 3:00 with no BHO but bends the case rim. An additional click open (10 clicks) and the rim is torn off the case again. Things I have verified: The bolt can be manually locked to the rear The gas tube extends to middle of the pivot pin cutout in the upper and is centered The gas block is aligned and has the usual carbon ring Bolt head-space has been checked and verified The gas key is tight, staked and in the correct location Primers are slightly flattened with no ejector marks or bolt swipes Buffer spring is not “stacking” in the extension The bolt is well lubricated The fired round count is 80 Troubleshooting I have done: Swapped the buffer spring from one of my working .308 carbine builds with AR-15 7” extension with no change Swapping the standard 3.8 oz buffer for the CAR-10 5.6 oz buffer allowed for decent extraction but no BHO Things I am contemplating: Is the gas port large enough at .080”? Is the spring length and coil count proper for a 7” extension? Some references say the proper 308 spring for 7” extension is 9-3/4” w/25 coils. Should I change to a 7-3/4” 308 carbine extension? Should I try a Sprinco Orange buffer spring? (supposed to be made for 308 w/7” extension) Should I dig a hole, bury this barrel and forget this caliber? Looking forward to your thoughts and comments.