308USK

Thanks! :)

Backpack SBRs...in a Vertx Gammut 3.0 backpack.

If anyone has doubts that @98Z5V knows his stuff...I'm here to tell you that he definitely DOES know his stuff! I had a pretty decent idea of what I needed to do, but was going through the process with too many steps (too many steps in machinist drill bits). In talking, after drilling out my gas port using a #42 and still not getting lockback on a 1-round test, I knew I needed to drill out larger...and was going to go up to a #41. After chatting, he convinced me to take it up to either a #39 or #38. I went to #39, borescoped the barrel to ensure things looked good, ensured the ABG was set to wide-open, thoroughly cleaned and lubricated the barrel...and waited for some free time to go to the range. Of course today was a cold, windy...absolutely crappy day, but I had the time and wanted to test the 8.2" barrel. Got everything set up and loaded one round in the magazine. Lockback test was conducted and was 100% successful Loaded four rounds in the magazine and check functionality. 100% successful. Loaded four more rounds in the magazine... 100% successful Ejected brass coming out at ~3:30 with my S&B 200gr subsonic. This weekend, I will disassemble the forend of the rifle, to loctite or rocksett things that are appropriately secured and reassembled. Backpack SBR#2 in the bag!

Hopefully you have this process all dialed in by the time I get back to Shenanigan Alley! LOL. Do some 300BO and 8.6 Blackout gel-block fun (of course, I'll pay for the gel blocks)...

Another sweet lookin' rig @98Z5V ... I know what your next build should be!! <laughing my ass off>

@98Z5V HELL YEAH!! That .260 is one sweet lookin' rig!!!

Thanks!!!!! I will be drillin' like a Texas oil-hand!!

Updated the video to zoom in on each shot, to better discern ejection location. Have my 2nd upper attached to my M4 lower, so I can run a normal buffer weight & spring. Have an H1 buffer weight for that configuration as well, so I can gather all the data I can when I can get to the range. Was planning to go on Monday after work, but have two appointments I forgot about, so it'll likely be Thursday or Friday before more data can be acquired.

Pistol length gas. I'll run my 2nd upper/barrel with my M4 lower and standard buffer (and bring an extra regular buffer weight) when I do my next testing late Monday afternoon. :)

@98Z5V Hope you can give my brain some ideas... Reusing the lower from my fully running 10.5” 300 Blackout, which includes JP SCS H2 Buffer Spring & Otter Creek Labs Hydrogen L - 7.62 suppressor New upper 8.2” 300 Blackout barrel Gas Port originally 0.0855” Adjustable Gas Block set wide open 1 round, 200gr S&B subsonic Rifle cycles, but will NOT lock back on empty mag ****************************** Drilled out using #43 machinists bit, re-assembled and tested. AGB wide open 1 round, 200gr S&B subsonic Rifle cycles but BCG does not lock back on empty mag. Will not run more than 1 round though.. ***************** Drilled out using #42 machinists bit, re-assembled and tested. AGB wide open 1 round, 200gr S&B subsonic Rifle cycles but BCG does not lock back on empty mag. Will not run more than 1 round though.. Brass ejecting at ~4:30-4:45 ################# Opened up AGB to 28 clicks 1 round, 200gr S&B subsonic Rifle cycles but BCG does not lock back on empty mag. Will not run more than 1 round though.. Brass ejecting at ~4:15-4:30 ################# Opened up AGB to 38 clicks 1 round, S&B 200gr subsonic Rifle cycles but BCG does not lock back on empty mag. Will not run more than 1 round though.. Brass ejecting at ~3:45-4:00 ################# Closed AGB to 18 clicks (wide open) Swapped JP SCS H2 for a JP SCS REGULAR (no tungsten weights) 1 round, S&B subsonic Rifle cycles but BCG does not lock back on empty mag. Will not run more than 1 round though.. Brass ejecting at ~4:30’ish ***Video below (if you zoom in to 300% and you can see the ejection pattern more clearly)*** I have another upper and 8.2" barrel; measured the gas port 0.0880. Assembled with the upper and put an AGB on it and will take it out to the range to test it with my regular 5.56 M4 lower and see how it fares that way. I have another JP SCS regular weight (as stated above), but DO have 1 tungsten weight I could add to make it an H1. On the 8.2" barrel I have drilled out to #42 drill bit size, based on the data I captured so far, the rifle still looks like it is undergassed. Am I off my rocker? Should I drill out using #41 drill bit? Should I add the tungsten weight to my current H2 buffer to make it an H3 buffer?

HOLY CRAP! 4.4 *MILES* ???? DAYUM!!

Copy all traffic. Update ya when I iron out the specifics.

Hey @98Z5V I can't get away until, at the earliest 3/29 - 4/5. As Deputy Department Leader, I will be acting Department Leader from 3/7 until 3/28... Hopefully we can still meet up whilst I am in Metro PHX (will be bringing my 2 SBRs to hopefully do some plinking in warmer weather). Cheers

@98Z5V more info for your 300BLK gas port database (caliper measured 5x for consistency): 10.5" Rosco Mfg 300BLK Bloodline barrel: 0.0850" 8.2" Rosco Mfg 300BLK Bloodline barrel: 0.0850" 10.5" Faxon Mfg 300BLK Gunner barrel: 0.1000"

I am looking at a visit with my Mom, sometime in late March. I've already got the 5320's filled out to bring 'em with me, just have to submit 'em. I'll call ya when things firm up and we can plan to do some pew pew fun...

Guilty as charged good sir! :'( After figuring out my 300BLK SBR, I was pretty content for all of about 4 months. Then I started working on another SBR...8.6 Blackout. I did peruse the board some, but too many "squirrel" moments and here we are. Just for shiits and grins, here are the two SBR's (multi-cam black for 300BLK and bronze-n-black for the 8.6 Blackout):

Spicy is good! LOL. Waiting, however, is NOT. Almost 3 mos in on the wait, even after sending an email to NICS Liason (with a short, terse response)...bah humbug. Hope you and the fam had a wonderful Christmas.

I have a Q Pork Chop awaiting approval from those ever-so-fine folks at BATF. This will mount to my 8.6BLK SBR (8" barrel)...

Oh nice!!! I am still awaiting my Q Pork Chop to be freed from ATF holding pattern. I do have to do the barrel break-in using supers which will also allow me to at least get the AGB baselined.

Wait...you couldn't get a 2-fer? WTH? LMAO Well done...

Thanks and yes, Vortex Strikefire II...

No thermal yet; will eventually put an AGM Rattler on...but for now, it's a Vortex Strikefire II (red/green selectable) with a Vortex 3x magnifier on a Unity FTC mount.

Thanks!

Have my 8.6BLK SBR build assembled and ready to go to the range for initial breaking / testing (note: I don't have the muzzle break on as I'm awaiting my Q Pork Chop approval. I do have a Faxon muzzle break that I will use for the short term)...until my Q Pork Chop comes in; then I will do the final dialing in for the rifle.

oh I am SO happy I did a search for 8.6 Blackout!! (lol) I am building an 8.6BLK SBR and can always use the knowledge gained by others! Haven't ordered my suppressor yet...but have all the parts in-hand. Taking it to Coloradokote soon, for Cerakote, then will do the build. FORM1 to be filed soon as well, cuz I already have the necessary details & pics needed to submit the Form1. Parts List: Next Level Arms Ascend full-ambi upper/lower receiver set SLR Rifleworks 7.1" DMPS Low M-Lok handguard Milspec Buffer Tube Mission First Tactical Minimalist Stock Law Tactical Folding Stock Adapter JP Rifle JPSCS2-10H2-LAW Buffer Spring TriggerTech AR10 Diamond flat trigger Toolcraft 308/6.5cm double-ejector BCG Radian-SD AR10 Charging Handle Radian Talon 45/90 Ambi Safety Selector Superlative Arms .875 AGB Pistol Length Gas Tube Faxon Firearms 8.6 Blackout 8” 1-3 Twist Big Gunner Contour Chrome Moly BBL CGS Hekate 338 DT M18x1.5 Time to buy some factory ammo for the build testing, as well brass, powder, large primers and bullets as I think it is time to start learning reloading (of course, I will have to put together a reloading station too...but hey, I'll get plenty of use out of it between 8.6BLK, 300BLK, .308, 7RM, 5.56 and 9mm (lmao). Tom (@98Z5V) I think you'll really like this one too. Will likely submit a 5320.2 to bring both of my SBR's with me to AZ when my wife and I come down at Thanksgiving for a week.