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  1. #1
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    Default 300 Blk Subsonic Vs Pistol Rounds

    In the recent 300 Blackout Pistol thread there was some discussion of using 300 BLK subsonic ammo for home defense:

    Not wanting to derail that thread with my question, I thought I'd start a new thread and ask here.

    I've been under the impression that subsonic 300 blk from an 8-9" barrel was pretty similar to pistol ammo in velocity and ft lbs of energy and that it was also less likely to expand at subsonic velocities than regular pistol projectiles.

    Based on that assumption, I've given the nod to an SI RMR Glock PDW for home defense when there are kids in the house (otherwise it's a Stakeout or PointMan).

    If I'm not correct about this, I'd be happy to be educated out of this opinion. I do realize that the AR platform has some ergonomic/points-of-contact/aiming/stability advantages over the Glock PDW but those benefits could be had in a 9mm AR pistol or something like a CZ EVO.

    These days, there are a few brands of high-end 300 BLK subsonics that are supposed to have good expansion so let's take non-expansion off the table as a criticism for the blackout.

    I also realize that supersonic suppressed 300 Blackout is vastly more powerful than anything from a pistol. I'm not interested in having rifle projectiles flying around in my house so let's stick with subsonics.

    So my question is; does a reliably-expanding 300 BLK subsonic from an 8" barrel have any significant ballistic advantage over a quality pistol round from a a full-size Glock PDW or CZ EVO (which has a slightly longer barrel than a Glock)?

    If it does, I'll buy some good, expandable subsonic ammo and switch to using my suppressed 300 Blackout for HD instead of the Glock PDW.
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  2. #2
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    240gr .300 comes with 1050fps, and 587 ft/# of energy.
    115gr 9mm runs 1150fps, and 338 ft/# of energy.
    Greg "Hyena" Nichols
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  3. #3
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    It's a bit of a squirrel, but do you mind sharing the reasons you only want subsonics in your house? Sound level is one concern I have, but a suppressor should help with that.

  4. #4
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    Quote Originally Posted by apamburn View Post
    It's a bit of a squirrel, but do you mind sharing the reasons you only want subsonics in your house? Sound level is one concern I have, but a suppressor should help with that.
    Better suppression and reduced risk of over penetration. I use 55gr, 556 for the same reason, the lighter bullet has a tendency to tumble once it hits something.
    Greg "Hyena" Nichols
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    #thinkinginviolence
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    Always entertaining, mildly offensive
    IANative: Indeed, when you grab Brent (or he grabs you), it feels like liquid unobtanium wrapped in rawhide... whereas Greg is just solid muscle wrapped in hate, seasoned w/ snuff and a little lead.

    http://www.warriortalk.com/showthrea...he-Obscenities

  5. #5
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    Quote Originally Posted by Greg Nichols View Post
    240gr .300 comes with 1050fps, and 587 ft/# of energy.
    115gr 9mm runs 1150fps, and 338 ft/# of energy.
    Thanks Greg. I appreciate it.

    Some other 9mm numbers:

    7.45 g (115 gr) Federal FMJ 1,180 ft/s (360 m/s) 355 ft⋅lbf (481 J)
    8.04 g (124 gr) Federal FMJ 1,150 ft/s (350 m/s) 364 ft⋅lbf (494 J)
    8.04 g (124 gr) Underwood FMJ +P 1,225 ft/s (373 m/s) 413 ft⋅lbf (560 J)
    7.45 g (115 gr) Winchester JHP +P 1,335 ft/s (407 m/s) 455 ft⋅lbf (617 J)
    8.04 g (124 gr) Cor‑Bon JHP +P 1,250 ft/s (380 m/s) 434 ft⋅lbf (588 J)


    45 acp numbers:

    230 gr (15 g) FMJ, Winchester 835 ft/s (255 m/s) 356 ft⋅lbf (483 J)
    165 gr (11 g) Hydra-shok, Federal 1,060 ft/s (320 m/s) 412 ft⋅lbf (559 J)
    230 gr (15 g) FMJ, Double Tap 960 ft/s (290 m/s) 471 ft⋅lbf (639 J)
    185 gr (12 g) JHP, Underwood 1,100 ft/s (340 m/s) 497 ft⋅lbf (674 J)
    145 gr (9 g) Glaser +P, Cor-Bon 1,350 ft/s (410 m/s) 587 ft⋅lbf (796 J)

    So it looks like the best 9mm is about 130 foot lbs less than the 300 subsonic.

    The Best 45 looks to be exactly the same energy.

    Though I also have a G17 PDW in 9mm, the one by the bedside (When the PointMan isn't by the bedside) is a .45 G21 PDW.

    Interestingly, Ft lbs aside, the expanding Lehigh defense bullet looks lots uglier expanded than any 45acp I've ever seen...So there's that.

    lehigh 194 2.jpg
    Lehigh 194gr Subsonic Maximum Expansion®

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  6. #6
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    Quote Originally Posted by apamburn View Post
    It's a bit of a squirrel, but do you mind sharing the reasons you only want subsonics in your house? Sound level is one concern I have, but a suppressor should help with that.
    Yeah as Greg said, better suppression and less over penetration.

    It'd be really interesting to me to see how different the penetration of interior walls would be (or the condition of the bullets after penetration) with a 55g from an AR pistol vs a 45acp from a Glock or subsonic 300Blk from an AR pistol.

    Anybody in the habit of shooting indoors that could illuminate?
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  7. #7
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    It's also more than just energy at the muzzle though. The higher mass of the round will more effectively transfer that energy to a soft body than the smaller/faster round. A couple of caveats are that in 5.56, which is horrible at transferring energy (though it's a high energy round due to velocity) due to the low mass of the round I prefer the 55gr because it tumbles once it strikes a medium, so the damage I don't get from energy transfer (crush damage and temporary wound cavity), I make up for in the wound channel as it bounces around the soft tissue. .45, 9mm, and .300 are far less likely to do that.
    Last edited by Greg Nichols; 01-30-2020 at 11:31 AM.
    Greg "Hyena" Nichols
    Instagram: tacfit_az
    Facebook: SI Instructor Greg Nichols

    #thinkinginviolence
    #tactisexual

    Always entertaining, mildly offensive
    IANative: Indeed, when you grab Brent (or he grabs you), it feels like liquid unobtanium wrapped in rawhide... whereas Greg is just solid muscle wrapped in hate, seasoned w/ snuff and a little lead.

    http://www.warriortalk.com/showthrea...he-Obscenities

  8. #8
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    Quote Originally Posted by Greg Nichols View Post
    Better suppression and reduced risk of over penetration. I use 55gr, 556 for the same reason, the lighter bullet has a tendency to tumble once it hits something.
    I'm not sure I follow on the over-penetration point. It doesn't matter what I'm shooting (maybe aside from frangible or .22 or something), inside of my home it's almost guaranteed that a bullet will go right through 1/2 to 1 inch of sheetrock and be just as deadly on the other side regardless of if it's a 9mm JHP plugged with sheetrock, a tumbling 5.56, or buckshot that just ripped a baseball-sized hole in the wall.

    I've shot 5.56 straight through sheetrock walls before and it didn't seem to phase it (may have been keyhole-ing by the time it exited, don't recall. But it did go straight through).

    So if penetration through interior walls is a fact of life, might as well have rifle or shotgun ballistics in my court, right?

    Caliber might be more influential on penetration of exterior walls or objects inside the home like a fridge, desk, heavy exterior door, furniture, etc... I suppose. And that could be a double edged sword.

    Anyways, I don't have the experience / creds that others (Greg) have, so I defer to your background, experience, and judgement. Someone correct me if I'm way wrong.

  9. #9
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    Quote Originally Posted by Greg Nichols View Post
    It's also more than just energy at the muzzle though. The higher mass of the round will more effectively transfer that energy to a soft body than the smaller/faster round. A couple of caveats are that in 5.56, which is horrible at transferring energy (though it's a high energy round due to velocity) due to the low mass of the round I prefer the 55gr because it tumbles once it strikes a medium, so the damage I don't get from energy transfer (crush damage and temporary wound cavity), I make up for in the wound channel as it bounces around the soft tissue. .45, 9mm, and .300 are far less likely to do that.
    So, if you had a 5.56 pistol stuffed with 55g and a 300BLK pistol with subsonics and a 300 pistol with supersonics and each was wearing a suppressor, which would you grab for a bump in the night?
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  10. #10
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    Another thing to consider...

    Yes some rounds hit harder than others and when all things are equal we want the hardest hitting projectile we can for the environment.

    But think about how quickly you can employ the gun. From 0 to 100mph, what can you get up and running quickly and easily? By that I mean not so much speed but EASE, smoothly and without awkwardness.

    If we have time, if we have the option to choose a better weapon system (which is a weapon that requires both hands), then we'll do so. When getting up to investigate a bump in the night, you are being proactive and have time to pick up your shotgun, or 300 SBR, or whatever of the 31 flavors you prefer.

    But going from zero (say in bed asleep, or with your hands full, or just busy with the every day stuff that we do in the home), you need something that you can easily access and operate with one hand. That is usually the pistol on the belt, or on the nightstand, in a holster on the bedside, etc. Of course nothing beats a pistol on the belt, but for a bedside gun, the PDW really shines. You can pick that up and use it just like a pistol, one handed, without strain or any real effort. Yes I know that a home invasion where they get to your bedroom before you can wake up is unlikely, but it doesn't have to be that stark of a situation. There are times when you want a weapon up NOW, even if that means there's no shooting immediately. The PDW is as easy to pick up as a pistol, but still has the benefit of a two handed weapon.

    I can pick up and aim any weapon I own one handed. But some of them are frickin awkward to do so. Picking up even a small 300 Blk SBR while you're in bed...presumably with someone sleeping next to you that you don't want to elbow or sweep (remember that we have no control over what THEY do or how they move in a moment of surprise), a handier weapon is much easier to control...making you more dangerous to potential enemies while being safer towards your loved ones.

    You can always hand off the PDW to the second in command while you access something bigger if you want.
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