Just built this AR Pistol....

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  • RuralRifleGuy

    Active Member
    Aug 16, 2018
    918
    Queenstown
    Recommendations for a caliber that performs well with either a 7.5" or 8" barrel? I have a 7" handguard that I need to use and I'm not sure what would work well out of a barrel in those lengths. I'm building a 300 BLK pistol with a 10.5" barrel so I want to avoid making a second 300 BLK pistol. It seems my other options are 6.5 Grendel, 6.8 SPC, .458 SOCOM, and .50 Beowulf. I don't want to go with a pistol caliber lower but if there are any other rifle calibers I should consider I'm open to suggestions. I'm building a full size 5.56 rifle so .223/5.56 are not calibers I'm considering for this.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,709
    Recommendations for a caliber that performs well with either a 7.5" or 8" barrel? I have a 7" handguard that I need to use and I'm not sure what would work well out of a barrel in those lengths. I'm building a 300 BLK pistol with a 10.5" barrel so I want to avoid making a second 300 BLK pistol. It seems my other options are 6.5 Grendel, 6.8 SPC, .458 SOCOM, and .50 Beowulf. I don't want to go with a pistol caliber lower but if there are any other rifle calibers I should consider I'm open to suggestions. I'm building a full size 5.56 rifle so .223/5.56 are not calibers I'm considering for this.

    Maybe I'm missing something here, but I don't know why you would want to put those high calibers(6.5 and 6.8) through a 7"-8" barrel. I do like the idea of the .458 or the .50BW though. Short barrel ARs shine when it comes to PC in 9mm and .40 S&W. I would not go over a 6" barrel for those.

    Maybe look at 243 Win?
     

    RuralRifleGuy

    Active Member
    Aug 16, 2018
    918
    Queenstown
    Maybe I'm missing something here, but I don't know why you would want to put those high calibers(6.5 and 6.8) through a 7"-8" barrel. I do like the idea of the .458 or the .50BW though. Short barrel ARs shine when it comes to PC in 9mm and .40 S&W. I would not go over a 6" barrel for those.

    Maybe look at 243 Win?

    They were referred to as the “best” alternative AR15 calibers listed online when I searched. Best is subjective so I figured I would ask here since I have zero experience with any of them. 458 was my first thought but I wasn’t finding much on appropriate barrel lengths, it seemed like everyone was going 300BLK. I know Columbia River has a 7.5” and 8” barrel for 458 but I’ve learned that just because something is available doesn’t mean it’s the best idea. Oddly 243 Win never came up in my searches.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,709
    They were referred to as the “best” alternative AR15 calibers listed online when I searched. Best is subjective so I figured I would ask here since I have zero experience with any of them. 458 was my first thought but I wasn’t finding much on appropriate barrel lengths, it seemed like everyone was going 300BLK. I know Columbia River has a 7.5” and 8” barrel for 458 but I’ve learned that just because something is available doesn’t mean it’s the best idea. Oddly 243 Win never came up in my searches.
    I know someone makes a .243, but not sure if in a short barrel. The problem with super short barrels is lack of dwell time. That is the portion of the barrel beyond the gas port. The shorter the dwell time, the less the round leaving the barrel is able to produce enough gas to function the rifle reliably. That's why 300 Blk has a pistol length gas port. It increase dwell for a gun that is meant to be an SBR .

    Sent from my SM-G965U using Tapatalk
     

    Russ D

    Ultimate Member
    Nov 10, 2008
    12,027
    Sykesville
    Whatever you do, don’t go to Hap Baker to shoot pistols. The range is closed for upgrades and you will end up at Baltimore’s Best and one of these might just follow you home. And so it begins.......
     

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    dreadpirate

    Ultimate Member
    Mar 7, 2010
    5,521
    Cuba on the Chesapeake
    Recommendations for a caliber that performs well with either a 7.5" or 8" barrel? I have a 7" handguard that I need to use and I'm not sure what would work well out of a barrel in those lengths. I'm building a 300 BLK pistol with a 10.5" barrel so I want to avoid making a second 300 BLK pistol. It seems my other options are 6.5 Grendel, 6.8 SPC, .458 SOCOM, and .50 Beowulf. I don't want to go with a pistol caliber lower but if there are any other rifle calibers I should consider I'm open to suggestions. I'm building a full size 5.56 rifle so .223/5.56 are not calibers I'm considering for this.

    6.5 Grendel does not do well in short barrels. 300 black does. Not sure about the others.
     

    RuralRifleGuy

    Active Member
    Aug 16, 2018
    918
    Queenstown
    6.5 Grendel does not do well in short barrels. 300 black does. Not sure about the others.

    Thanks for the follow up, I actually went the 300 blackout route with it and it works great out of the 7.5" barrel I picked up. Loud but fun, need to get a suppressor for it. Decided to do a 18" Grendel rifle build to scratch my itch for a different caliber.
     

    Russ D

    Ultimate Member
    Nov 10, 2008
    12,027
    Sykesville
    I think the Scorpion just got some stiff competition. YHM receivers, Ballistic Advatage barrel, BCM rail, CMC trigger, strike enhanced lpk, tailhook mod1
     

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    dreadpirate

    Ultimate Member
    Mar 7, 2010
    5,521
    Cuba on the Chesapeake
    Guess it depends on “short”. The PSA 12” Grendel’s are getting great reviews.

    Let me revise my statement; 6.5 Grendel does just fine with a short barrel, but really shines (i.e. realizes its full potential) with a 20 inch or so barrel. I agree, that does not mean it performs poorly with a shorter barrel.
     

    JimNorth

    Active Member
    May 4, 2018
    140
    The Cloud
    I think the Scorpion just got some stiff competition. YHM receivers, Ballistic Advatage barrel, BCM rail, CMC trigger, strike enhanced lpk, tailhook mod1

    Nice compact package. How do you like the tailhook mod1? I'm considering the tailhook mod1, tailhook mod2, & sba4 but haven't been able to try any.
     

    Russ D

    Ultimate Member
    Nov 10, 2008
    12,027
    Sykesville
    Nice compact package. How do you like the tailhook mod1? I'm considering the tailhook mod1, tailhook mod2, & sba4 but haven't been able to try any.

    The tailhook is very solid and well made. It’s also extremely light. I wanted something minimalist and it fit the bill perfectly.
     

    scout6

    Active Member
    Sep 28, 2016
    599
    Ceciltucky
    My first build. This was a fun project, and I really enjoyed shooting it. Took over a year start to finish. Looking forward to more range time as I only brought 3x 20 rounds to test and sight in the holo.

    Started out with a box of Remington 120 gr. OTFB supers w/o the suppressor, and a box each of Remington 220 gr. OTFB and Hornady Black 208 gr. AMAX subs with.

    All 3 fired flawlessly, no FTF or FTE. Didn't save the target reports, as I was more concerned with functionality and getting the eotech aligned. Tried to boresite with a green laser, but was too bright, even at 25 yrd to align. Ended up having to do it the old fashioned way and walk it to target. Once aligned, all shots were within the close enough to center mass of an 8 inch circular target for my tastes considering at 100 yards, it was a challenge for my eyes to get the red dot on the holo and the red bullseye dot to align.

    Another shooter on the range came over to make sure I hadn't shot a squib once I switched to subs w/ the socom and check out the rig. Surprisingly quiet.

    Ruger lower
    Hardened Arms 10.5 300 BLK completed upper *no longer in business
    SB PDW
    H2 Buffer
    B-GRF Geissele Trigger
    Magpul K2 grip
    Magpul 300 blk standard capacity mags with dyed base plate
    S&W lower parts kit
    Surefire Warcomp
    Surefire SOCOM 300
    Eotech Holo on a Kinetic SDELOK detachable

    Thinking of replace the trigger guard and mag release with red hardware to match the mag plates for quick ID. BIS and maybe a laser/light combo down the road.
     

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