300 Blackout test, as promised

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  • rsilvers

    Active Member
    Dec 24, 2010
    113
    With subsonic the accuracy is about the same. With supersonic, 16 inch is more accurate.
    We get 0.85 inch 5 shot group averages based on 50 rounds with 110 grain ammo in 16 inch 1:8 test barrels with the 300 BLK chamber. With 9 inch actual guns, more like 1.3 MOA.

    For some reason the 110 grain Sierra and Berger bullets are most accurate. It seems to like short bullets. 112 grain benchrest bullets did awesome also. Not all guns like to feed the short bullets.
     

    BenL

    John Galt Speaking.
    BTW... any issues with keyholing?

    In the 80 rounds I shot, no. If you look at the photo at the top, the two top holes look like they went in slightly askew, but that could have just been the way the paper was laying on the backing. I only got to shoot to 100 yards. When I get my hands on some quantity of brass, I'll load up a bunch and try them at 200 yards.
     

    SCARCQB

    Get Opp my rawn, Plick!
    Jun 25, 2008
    13,614
    Undisclosed location
    In the 80 rounds I shot, no. If you look at the photo at the top, the two top holes look like they went in slightly askew, but that could have just been the way the paper was laying on the backing. I only got to shoot to 100 yards. When I get my hands on some quantity of brass, I'll load up a bunch and try them at 200 yards.

    I'm just concerned about baffle strikes. I'm going to have to make sure the 220 grain projectile stabilizes adequately before using a can.
     

    boatbiologist

    Active Member
    Nov 6, 2008
    612
    Glen Burnie
    With the extra bore space of the 9mm can on the .30 cal bullet, I would think a baffle strike with that set up would be very unlikely. Would love to hear how it sounds. Sounds like a cool build!
     

    Russ D

    Ultimate Member
    Nov 10, 2008
    12,029
    Sykesville
    With subsonic the accuracy is about the same. With supersonic, 16 inch is more accurate.
    We get 0.85 inch 5 shot group averages based on 50 rounds with 110 grain ammo in 16 inch 1:8 test barrels with the 300 BLK chamber. With 9 inch actual guns, more like 1.3 MOA.

    For some reason the 110 grain Sierra and Berger bullets are most accurate. It seems to like short bullets. 112 grain benchrest bullets did awesome also. Not all guns like to feed the short bullets.

    What about Vmax's? I find them to be very accurate in most applications. The short flat base design would seem to jive with the other bullets you are having good results with.
     

    rsilvers

    Active Member
    Dec 24, 2010
    113
    For flat base bullets which don't protrude past the case neck, heavier bullets have more energy. The exact energy difference is best to compare in the same barrel. There are gel tests on Hornady web site.
     

    rsilvers

    Active Member
    Dec 24, 2010
    113
    I would use a 2.260 OAL for a bolt gun, and 2.120 for an AR. The amount of Re-7 will be in the 10-11 range. Just load it to 1000 fps. With the standard deviation in velocity, 1050 will too often go supersonic, especially in colder weather. Also, bullet flight noise jumps up a lot around 980 fps.
     

    BenL

    John Galt Speaking.
    I would use a 2.260 OAL for a bolt gun, and 2.120 for an AR. The amount of Re-7 will be in the 10-11 range. Just load it to 1000 fps. With the standard deviation in velocity, 1050 will too often go supersonic, especially in colder weather. Also, bullet flight noise jumps up a lot around 980 fps.

    For the sake of clarity and safety:

    AR w/ 16" barrel:

    AAC Blackout brass resized with Forester dies
    primers = Remington 7 1/2
    COAL = 2.120"
    Powder = Reloader 7
    Powder Weight = (work up) 9.0gr, 9.5gr, 10.0gr, 10.5gr
    Bullet = Hornady 208gr. Amax
    No Crimp

    I'm looking for ~1000 fps, but stay above 980fps.

    Is this correct?
     

    EngageSmith

    ,
    Industry Partner
    May 31, 2011
    297
    Kensington, MD
    I'm just concerned about baffle strikes. I'm going to have to make sure the 220 grain projectile stabilizes adequately before using a can.

    Can you set up multiple target frames in a straight line, spacing them a few feet apart? 10-15 paper targets out to 50 feet would definitely let you know if the bullet is tumbling or not.

    For what it's worth, I built a 16" .300-221 rifle during my time at PGS. I used a Shilen 1:8 barrel, reamed with PTG reamer. I used a pistol-length gas system, with a JP Enterprises adjustable low-profile gas block. I can't remember the gas port diameter but I think it was around 0.074-0.075". I still have the reamer I used in my toolbox in the workshop if anyone is interested.

    I've only put around 100 rounds through it, and functioning has been mostly good. A few rounds caught the edge of the chamber and tore the case mouth up. I may not have put enough of a chamfer on the edge of the chamber, and I plan on re-doing that once our lathe is up. Other than that, no problems extracting/ejecting.

    Last time I shot it, I closed the gas system off, and ran it single-shot with an H3 buffer. Ran it with my YHM Phantom .308 can, and even with a 180gr bullet, it was pretty quiet. If I can ever figure out how to get the video from my BlackBerry to YouTube I'll post it up.

    Has anyone done a build with a Noveske barrel yet?
     
    Can you set up multiple target frames in a straight line, spacing them a few feet apart? 10-15 paper targets out to 50 feet would definitely let you know if the bullet is tumbling or not.

    For what it's worth, I built a 16" .300-221 rifle during my time at PGS. I used a Shilen 1:8 barrel, reamed with PTG reamer. I used a pistol-length gas system, with a JP Enterprises adjustable low-profile gas block. I can't remember the gas port diameter but I think it was around 0.074-0.075". I still have the reamer I used in my toolbox in the workshop if anyone is interested.

    I've only put around 100 rounds through it, and functioning has been mostly good. A few rounds caught the edge of the chamber and tore the case mouth up. I may not have put enough of a chamfer on the edge of the chamber, and I plan on re-doing that once our lathe is up. Other than that, no problems extracting/ejecting.

    Last time I shot it, I closed the gas system off, and ran it single-shot with an H3 buffer. Ran it with my YHM Phantom .308 can, and even with a 180gr bullet, it was pretty quiet. If I can ever figure out how to get the video from my BlackBerry to YouTube I'll post it up.

    Has anyone done a build with a Noveske barrel yet?

    My build has a noveske barrel.
     

    BenL

    John Galt Speaking.
    UPDATE

    I loaded up some Hornady 208gr Amax bullets with Reloader 7 in the Blackout and shot them at the range, today.

    I loaded 11.0gr, 10.5gr, 10.0gr, 9.5gr, and 9.0gr of Reloader 7 with a COAL of 2.20" and Remington 7 1/2 primers. I only ended up shooting the 11.0gr and 10.5gr (with subsonics, you work from the top load), because the others would have been too slow, with a target speed of 1000fps. The brass was once-fired, resized with Forester dies, and trickled to the exact 1/10th of a grain.

    The 11.0gr of Reloader 7 had an average speed of 1013.4fps with a standard deviation of 21.97 and an extreme spread of 46fps (n=10), and the 10.5gr was average speed of 997.0fps with an SD of 29.3fps and and extreme spread of 73.5 (n=10).

    The 11.0gr looks like it might be a winner. I'm tempted to bump it a little, but with the SD, would still like to keep the max speeds subsonic (the fastest 11.0gr was 1037fps.) I may be able to bump it a hair (11.2gr), but not much more.

    I'm going to load 50 of the 11.0gr and test the accuracy to see if it's any different than the factory 220gr. loads.
     

    Russ D

    Ultimate Member
    Nov 10, 2008
    12,029
    Sykesville
    I loaded up some Hornady 208gr Amax bullets with Reloader 7 in the Blackout and shot them at the range, today.

    I loaded 11.0gr, 10.5gr, 10.0gr, 9.5gr, and 9.0gr of Reloader 7 with a COAL of 2.20" and Remington 7 1/2 primers. I only ended up shooting the 11.0gr and 10.5gr (with subsonics, you work from the top load), because the others would have been too slow, with a target speed of 1000fps. The 11.0gr of Reloader 7 was average an average speed of 1013.4fps with a standard deviation of 21.97 and an extreme spread of 46fps (n=10), and the 10.5gr was average speed of 997.0fps with an SD of 29.3fps and and extreme spread of 73.5 (n=10).

    The 11.0gr looks like it might be a winner. I'm tempted to bump it a little, but with the SD, would still like to keep the max speeds subsonic (the fasted 11.0gr was 1037fps.) I may be able to bump it a hair (11.2gr), but not much more.

    I'm going to load 50 of the 11.0gr and test the accuracy to see if it's any different than the factory 220gr. loads.

    I wish I could have stayed around and watched the test. It looks like you've already got it dialed in pretty good! Thanks for the good work and reports.
     

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