308USK

Guess I forgot to post pix of the 300BLK with the can attached...(my bad! LOL). Doing another SBR build...this time in 8.6 Blackout. HOOYAH!

LOL My Toolcraft 5.56 DLC BCG is pretty nice; have a little wear showing (very small amount), but that could be due to the light lubrication on my first run @ the range (thought my gun lube bottle was more full than it actually was, so I only had a wee bit to lube up high-friction places). Since then, I have made sure I put some MilTec1 on before I go to the range (lol).

Still working to dial in the gas/buffer for subsonic ammo (whilst I wait for my suppressor to be set free [lol]), but supersonic ammo runs like a champ! Parts list: Spikes Tactical Viking lower Spikes Tactical M4 upper CMMG ambi-safety selector Strike Industries ambi-magazine release Strike Industries Extended Bolt Catch Radian Raptor-LT charging handle Toolcraft 5.56 BCG (DLC) Strike Industries 10" M-Lok handguard Rosco Mfg 10.5" Bloodline pistol length gas 300BO barrel Superlative Arms .750 Adjustable Gas Block JPSCS2-15H2 buffer spring Geissele SSA-E trigger Magpul K2+ grip Magpul M-Lok AFG Magpul stock with buffer tube SureFire M640-DFT-Pro light Unity Axon SL switch with M-Lok mounting kit Sig Sauer Romeo 4XT-Pro red-dot optic Sig Sauer Juliette 3x Magnifier Multicam Black cerakote (ColoradoKote did the work) @98Z5V pics for now (LOL)

Interesting video! Finished my 300Blackout build today (last item on the build list came in). Parts list: Spikes Tactical Viking lower Spikes Tactical M4 upper CMMG ambi-safety selector Strike Industries ambi-magazine release Strike Industries Extended Bolt Catch Radian Raptor-LT charging handle Toolcraft BCG (DLC) Strike Industries 10" M-Lok handguard Faxon 10.5" Gunner-profile pistol length gas 300BO barrel Aero Precision .750 Adjustable Gas Block JPSCS2-15H2 buffer spring Geissele SSA-E trigger Magpul K2+ grip Magpul M-Lok AFG Magpul stock with buffer tube SureFire M640-DFT-Pro light Unity Axon SL switch with M-Lok mounting kit Sig Sauer Romeo 4XT-Pro red-dot optic Sig Sauer Juliette 3x Magnifier Here's a look-see...

Hey Brother! I'll check that out for sure. Currently wrapping up a 300BO SBR build (10.5" barrel). Spikes Viking lower, M4 upper, Strike Industries M-Lok handguard, Sylvan Arms folding stock adapter (right side flip), SIg Romeo 4XT-Pro + Juliet 4x magnifier, Magpul AFG, SureFire M640-Pro light with Axon SL switch. Have a OCL Hydrogen-L can currently in the holding pattern (65 days and counting).

He drilled out using a #47 bit, so just hair over 0.07850. HA! Keep YOU straight? Not a prayer in hell sir... (rotf)

Follow-up... My brother and I hit the range today. His rifle, post gas-port drill out is cycling and working 100%. He even put a can on and adjusted the gas block a couple of clicks and the rifle still worked 100%. He's happy... Thanks again, to the knowledgeable peeps here!

Hey Gang...my Brother has not had a chance to get to the range yet. The barrel has been drilled (using a #47 bit) and everything put back together. Hopefully this coming week won't quite so hectic and he can get to the range to confirm proper cycling and whatnot. ;) Note: The original BCG was also a POS (just pulling out of the rifle while on the workbench at home required some substantial effort. We put the BCG from my large frame AR in (.308) just for fitment verification. It went in smooth as butter and came out just as easily...so he bought a new BCG and it went in smoothly as well, so that should eliminate that issue.

Okay gents, have some information. 1) Barrel length is 22" 2) Rifle-length gas 3) 6.5CM 4) Gas Port Size measured 5x with 2 different sets of calipers; consistently as seen in attached picture +/- a wee bit. What "should" the gas port size be for this configuration? (He's ready to drill, once he knows the proper port size).

Will ask my brother to get a pic of the ejector face as well as the gas port diameter measurement! Will reply once I have info...thanks again y'all...

My brother will be measuring gas port hole size, but will also inspect the feed ramp area... Thanks to all helping...always appreciated!

Journal size is .750; I will have my brother measure the actual hole size with digital caliper (oh wait...I had to drill baby drill myself (lmao). DAMN why didn't I think of that?) and report back. (insert facepalm here)

Hey gang, my brother was sighting-in his 6.5CM that he just put a new barrel on...hoping y'all can help identify the issue: Background: My brother has built countless rifles (small-frame AR's, large-frame AR's, yada yada yada), so this one should not be any different; but, for some damn reason it is. The upper is not one he built, so there are some unknowns there. I can get the details, if it is important/needed, to identify the issue. Rifle used to cycle consistently and would not have any issues. The barrel was too damn heavy, so my brother bought a new lighter-weight barrel and put it all together. Rifle has an adjustable gas block (he has cans, so he uses AGB's just out of habit). Issue Description: Round chambers and will shoot the first round, but then will not feed the next round. He started with the AGB wide open, then down to standard open (18 clicks open), then +/- a small # of clicks, trying to balance gas vs. mass. More often than not, the rifle would require dropping the mag and clearing the jammed round (see attached pic). Hopefully the brainiacs on the forum can help narrow down what is causing the issue!

Pictures/video ... or it doesn't happen! (LOL, I couldn't help myself...I apologize)

I had to add a 2nd tungsten weight to my SCS, to get my LR308 working (after a crap-ton of help from the fine folks here [thanks again gang!]). Now my rifle runs like a champ; probably 1000 rounds through it since June 2022 and only a few mis-fires during that initial period of getting the gas & mass squared away.

Gas tube is too short for sure. Gas port is DEFINITELY too small. I'd drill (drill baby drill, as has been said on the forum)...!!!!!

What @shooterrex said! Gas port is too small...and/or buffer spring & weight are incorrect.

FWIW, I had to open up my gas port, so I got a couple of #'d drill bits (#41 and #42) and started small. Taped the drill bit at a point where it would go into the barrel a little ways, but NOT all the way and nick the bottom of the inside of the barrel. (note: I used a corded drill, lubed the hole with 3-in-1 oil and drilled slowly but methodically holding the drill as perpendicular to the barrel as humanly possible!) I had used my digital micrometer to measured the opening size, so I knew where I was starting (0.0835"). When I finished, I was at 0.0945"... I took the rifle to the range, opened up my adjustable gas block to WIDE OPEN and shot a couple rounds. The rifle cycled...YAY! Closed the AGB down to the factory spec (Superlative Arms AGB. 18 turns from closed). Shot the rifle again. Rifle cycled pretty much perfect, but really close to the 3:00 position, so I opened up 1 click...shot again. 3:15'ish. 1 more click (20 turns total now). Shot again...3:20'ish. Good enough for me!

There are tons of "options" when it comes to springs, but as @shooterrex stated, it's really a matter of mass (buffer & spring) vs. gas. For example, my build (using Aero Precision upper/lower/BCG/18" barrel with rifle-length gas tube, Superlative Arms Adjustable Gas Block and carbine length buffer tube) required me to do some tuning because the gas port on the barrel was NOT drilled to proper specifications. After asking for help/guidance here (thank God for the knowledge-base on this forum), I ended up having to purchase a stock Armalite Spring and 5.3oz heavy buffer to verify my rifle cycled properly. It did not. Gas port was too small. Had to drill out gas port. blah blah blah and eventually I got the rifle running like a dream! Long story short, every large frame AR has its' own character and once you identify the proper mass vs. gas proportions, where your rifle will cycle correctly and eject casings at 3:00 -> 4:15'ish, you will love the large frame AR platform (in my opinion). One other thing to note: the large frame AR's prefer to be shot WET (meaning well lubricated), whereas the AR15/M4 platform isn't as persnickety! I'm sure the heavy-hitters with WAY more knowledge than I have will respond. Good luck!

Well done! Looks along the same lines as the Cerakote camo job done on my LR308. ;)

None of my business, but why are you shooting steel cased ammo? (just a personal curiosity; every type of steel cased ammo has been nothing short of $h!t for M4/LR308 for me). Now, for a thought to help (maybe): Do you have a digital caliper? If so: 1) Measure the case width of the steel ammo, record the measurement 2) Measure the head width of the steel ammo, record the measurement 3) Measure the case width of the brass ammo, record the measurement 4) Measure the head width of the head ammo, record the measurement With the information above, you might be able to ascertain why the steel ammo is working properly and the brass ammo IS NOT. Best of luck.

Best of luck! I had issues after the build of my LR308; had to drill the gas port to fix...but in the process, I removed my JP SCS and got a stock Armalite spring and 5.3oz buffer to ensure 'standard' parts blah blah blah. Once I got the gas side squared away (drilled out, open up gas block wide open, confirmed proper cycling, adjust gas block down for proper timing, then re-install the JP SCS and verify cycling is still proper (it was) and voila). Will keep the stock spring & buffer for any other LR308/AR10 builds I do.

Standard spring with 5.3oz buffer, open gas block WIDE OPEN to start, then dial in after issue is resolved.

If you are running an adjustable gas block, remember to open it up WIDE OPEN for the first round of shooting. Also remember to run the gun wet...so as to allow proper seating/wearing in. :) Aero Atlas R-One or S-One are high-profile, if that helps.