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Thread: PDW length barrels.....300BLK or 5.56?

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    PDW length barrels.....300BLK or 5.56?

    Barrels less than 10.5". Let's say 8" or 9". Let's also establish that we're talking about out to 200 meters max. Now a PDW is obviously intended for CQB-type distances but if need be you could reach out and touch someone at intermediate ranges. Not talking a hill-to-hill shootout in Afghanistan but within 200m.

    From chrono data I've seen over the years 5.56 NATO (not talking .223) starts to really fall off terminal performance-wise with barrels < 10.5". However, 300BLK is designed for short-azz barrels, namely in the "PDW" envelope I'm referring to.

    So the hypothesis I'm putting forward is that in barrels shorter than 10.5" the 300BLK will surpass 5.56 terminal performance out to 200 meters. You go 10.5" or longer and the 5.56 shines (with good ammo of course).

    Fire away.
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    Quote Originally Posted by ABNAK View Post
    So the hypothesis I'm putting forward is that in barrels shorter than 10.5" the 300BLK will surpass 5.56 terminal performance out to 200 meters. You go 10.5" or longer and the 5.56 shines (with good ammo of course).

    Fire away.
    Lol. I'll bite, although I am not the most versed with 300BLK.

    Per R Silvers PDF, find the Max Effective Range slide:
    300 BLK (125gr @ 2220fps) from a 9 inch barrel has the same energy at the muzzle as a 14.5 inch M4, and about 5% more energy at 440 meters.


    https://www.google.com/url?sa=t&rct=...3PEYqR62ezc0nq

    I would put that inside 200 meters, the 9 inch 300 BLK is more effective that any sized 5.56 (based on the "size efficiency" of the package). You can have supersonic mags and subsonic mags.
    Last edited by Rayrevolver; 12-04-17 at 07:35.

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    Quote Originally Posted by Rayrevolver View Post
    Lol. I'll bite, although I am not the most versed with 300BLK.

    Per R Silvers PDF, find the Max Effective Range slide:
    300 BLK (125gr @ 2220fps) from a 9 inch barrel has the same energy at the muzzle as a 14.5 inch M4, and about 5% more energy at 440 meters.


    https://www.google.com/url?sa=t&rct=...3PEYqR62ezc0nq

    I would put that inside 200 meters, the 9 inch 300 BLK is more effective that any sized 5.56 (based on the "size efficiency" of the package). You can have supersonic mags and subsonic mags.
    I was a big drinker of the R. Silvers 300Blk cool aid for awhile. The velocity you have listed is actually for a 125 grain bullet through a 16 inch barrel. 9 inch velocity is 2050. Silvers/AAC purposefully compared results from a 16 inch 300 blackout barrel to a 14.5 5.56 barrels to cherry pick results but I do think the OP is correct in his assumption. I plan on jumping back into 300 BLK in the near future with an 8.5-9 inch barrel. With hand loads the 110 grain Barnes TAC TX blacktip should achieve 2250-2300 without much problem ( I pushed them to 2500 in a 16 inch no problem)and they will offer some expansion down to 1350-1400 FPS so I think the cartridge with that bullet definitely has an advantage over 5.56 in sub 10.5 barrels.
    Last edited by Nightvisionary; 12-04-17 at 16:07.

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    Sorry for the quality of this image. I had it saved from several years ago, and don't remember the source. The go to projectile today is still the 110 gr. Barnes TAC TX as NV mentioned.

    300-chart.JPG
    Last edited by darr3239; 12-04-17 at 18:00.
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    Quote Originally Posted by Nightvisionary View Post
    I was a big drinker of the R. Silvers 300Blk cool aid for awhile. The velocity you have listed is actually for a 125 grain bullet through a 16 inch barrel. 9 inch velocity is 2050. Silvers/AAC purposefully compared results from a 16 inch 300 blackout barrel to a 14.5 5.56 barrels to cherry pick results but I do think the OP is correct in his assumption. I plan on jumping back into 300 BLK in the near future with an 8.5-9 inch barrel. With hand loads the 110 grain Barnes TAC TX blacktip should achieve 2250-2300 without much problem ( I pushed them to 2500 in a 16 inch no problem)and they will offer some expansion down to 1350-1400 FPS so I think the cartridge with that bullet definitely has an advantage over 5.56 in sub 10.5 barrels.
    Yeah, it's a very narrow niche category but in < 10.5" barrels the 300BLK is in it's element. The 5.56 is designed for "longer" barrels than 8" or 9" and IMHO will overtake the 300 in those categories. But the little PDW scene? I'll take 300BLK.
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    If burning powder is the name of the game- a larger bore will always do better than a smaller one.


    338 federal does better than 308

    6.5 grendel willl do better in a shorter barrel than 224 valkyrie

    300blk will do better than 556 ect
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    Quote Originally Posted by turnburglar View Post
    If burning powder is the name of the game- a larger bore will always do better than a smaller one.


    338 federal does better than 308

    6.5 grendel willl do better in a shorter barrel than 224 valkyrie

    300blk will do better than 556 ect
    Good point.
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    Found some actual user numbers last night from both TOS and M4C. With respect to muzzle energy, Barnes 5.56 70gr in a 14.5" barrel = Barnes 300BLK 110gr in a 9" barrel

    Just challenging your hypothesis:
    If you want a 14.5" or shorter, go 300BLK. If you want a 16" then get a 5.56.

    For whatever the reason, I like shooting my suppressed 11.5" 5.56 better than a suppressed 9" 300BLK. If I had to choose 1 to keep, it would be the 5.56.

    Just based on energy numbers, I am not sure how you can defend a 14.5" 5.56 when a 9" 300BLK can get the job done. Real world, SBR issues, rail space, ammo costs etc mean its not just an energy numbers issue of course.

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    I always looked at anything under 10.5" in 5.56 as a range toy/noise maker. My personal preference is 11.5-14.5" in 5.56. I'd be willing to go shorter in .300blk, which puts it in PDW territory.
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    You guys are making me want (need) a 300. Do 300 supers from a 10.5 suppress significantly better than 5.56?

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