Supersonic load on 4.5" barrel able to defeat IIIA body armor?

[Omega]

Thank you for sharing this info, but I'm wondering how close this test compares to supersonic FMJ being fired from 4.5"ish barrel, at very close range (25 yards). Judging by other answes that you guys gave me, I imagine it would penetrate. Were the rounds you used for this test expansive? Were they super or subs? Thanks again, bro!

Standard M855 ammo, so supers, and shot out of a 14.5 barrel. Not sure what a 4.5" barrel will do, the M855 is a FMJ, so that part is known though possibly the steel core made it mushroom and break apart easier, so that may be why it was defeated most times. The trick is velocity and for the round not to deform/mushroom so it can go through. If it expands, it gives more surface area for the armor to act upon and slow down the projectile.

[Shushh]

I'm late the the party and new around here. As well as sympathize with what the OP is/was trying to accomplish. But I'm curious about some fundamental questions that weren't asked.

Primarily why an AR at all? If length is so important isn't a pistol(not AR pistol but like a Glock or 1911) better? With such a short barrel the performance of even 300BLK is so diminished that it becomes near pointless. Where as for even less overall length of the weapon a pistol with a quite long barrel can be built. It can then be chambered in some darn potent cartridges and have the barrel to push it. For example a long slide 1911 chambered in 9x25 Dillon has no problem getting a 90gr bullet over 2000fps. With the right bullet that should defeat IIIA. Don't think that's enough, step up to 3800 Casull, or go further and work with a Desert Eagle or AutoMag platform. The point being that even with a mag in grip pistol platform it's doable and likely better then such a short barreled AR.

Additionally maybe it's better to not worry about piercing the armor. With soft body armor even if the round doesn't penetrate getting hit with something say 10mm and up is going to really F someone up. This concentrating on penetrating soft armor only matters if they are wearing it and you hit it. But hit anyone anywhere except on a hard rifle plate with something like 460 Rowland and they are F'd. Like above a long slide(6" barrel") 1911 can reliably sling a 230gr 45 caliber flying ashtray at 1400fps. That's more muzzle energy and a heck of a harder hit then you'll get out of any 300blk from a 4.5" barrel.

[Ghost12three]

I'm late the the party and new around here. As well as sympathize with what the OP is/was trying to accomplish. But I'm curious about some fundamental questions that weren't asked.

Primarily why an AR at all? If length is so important isn't a pistol(not AR pistol but like a Glock or 1911) better? With such a short barrel the performance of even 300BLK is so diminished that it becomes near pointless. Where as for even less overall length of the weapon a pistol with a quite long barrel can be built. It can then be chambered in some darn potent cartridges and have the barrel to push it. For example a long slide 1911 chambered in 9x25 Dillon has no problem getting a 90gr bullet over 2000fps. With the right bullet that should defeat IIIA. Don't think that's enough, step up to 3800 Casull, or go further and work with a Desert Eagle or AutoMag platform. The point being that even with a mag in grip pistol platform it's doable and likely better then such a short barreled AR.

Additionally maybe it's better to not worry about piercing the armor. With soft body armor even if the round doesn't penetrate getting hit with something say 10mm and up is going to really F someone up. This concentrating on penetrating soft armor only matters if they are wearing it and you hit it. But hit anyone anywhere except on a hard rifle plate with something like 460 Rowland and they are F'd. Like above a long slide(6" barrel") 1911 can reliably sling a 230gr 45 caliber flying ashtray at 1400fps. That's more muzzle energy and a heck of a harder hit then you'll get out of any 300blk from a 4.5" barrel.

Hey, Shushh! I liked how different your approach was, and I think it's worth telling you why I don't think it is a good option for me, still, thanks a lot for giving me this wildcat pistol cartridges info. I didn't know about this powerful pills for Glocks (with barrel swaps) or 1911.

My hands aren't big enough for huge pistol grips such as Desert Eagle's, so they are a no go.

I don't trust the 1911 platform. Not trying to say that it's really a bad one, it is not, but I believe Glocks are more reliable therefore wouldn't pick a 1911 for any serious role, such as service pistol o HD firearm. That would leave me with the AR PCC and the Glock.

the AR platform lets me put a NV compatible EOTech EXPS3-0 with a 5/8" riser on it, an ERGO Swift Grip, BCM Gunfighter Vertical Grip-Mod 3 M-LOK, SureFire M600DF and B. E. Meyers MAWL-C1+. Oh, and the Lancer translucid magazines are very reliable (I like translucid mags), but from what I've seen so far, ETS is not as good as Glock OEM. For these things, a Micro RONI, a PCC or an SBR are required. A 1911 or a Glock by itself can't handle the OPERATOR WITHIN OURSELVES!!! Hahahaha

The shortest barrel I've found so far is one from KAK Industry, measuring 4.75". As I'm gonna use their Micro Length Gas Tube and compatible gas port distance (micro length gas system), I thought that it would be more adequate to go from a 4.500" to 4.750" custom made barrel. Here is some data on supersonics through this barrel.

"All rounds listed below cycled through both barrels with mil-spec BCG and standard weight buffer.  Last round locked the bolt back with each ammo, unsuppressed.

Barnes RangeAR 90gr:

4.75" Average 1961 fps.  Standard deviation (SD) 21

Reaper Controlled Chaos 110gr:
4.75" Average 1792 fps,  SD 31

Barnes Tac-TX 110gr:
4.75" Average 1846 fps, SD 6

Federal All-Copper 120gr:
4.75" Average 1662 fps, SD 45

ADI MSR 125gr Sierra Matchkings
4.75" Average 1651 fps, SD 60

Ammo Inc Jesse James 150gr soft point
4.75" Average 1613 fps, SD 18"

I consider 1961 fps a very good speed (90-gr). As long as it easily goes trough IIIA armor, I think it is better than any PCC or Glock. With a pistol I only get one solid point of contact. Being very small would be nice, but I'd prefer to have the second and third points of contact: a vertical foregrip and a stock. That can be accomplished using something like a CAA Micro RONI, but then the footprint of the firearm gets close to that of an SBR or PCC when I attach a sound suppressor. *The 9x21 is extremely loud and has a considerable amount of muzzle flash too.* And here is a drawback that it would have in comparison with an AR platform. The extra length of that can would not translate as extra rail space because of a longer handguard. There is no such thing (not that I'm aware of) like a over the suppressor handguard for a Micro RONI. If it was an AR, I could place my VFG closer to the front end of the gun, aiding controllability and recoil management. Now I'm left with 2 types of AR-15s: PCC or an SBR. And here's why I pick the 4.75" 300 BLK SBR:


Shorter length 30-round magazine
Supersonic 90 gr 300 BLK is only 39 fps shy of reaching 2000 fps
I'm going to use it within 15 yards, so I won't need to worry about bullet deceleration
I won't need a longer than 5" barrel to reach this 2k fps mark.


I don't want to count on the "hard punching pill" that stops the bad guy just because of pain when hitting and not piercing his vest because the chance of him being under the influence of heavy narcotics like meth is high (see what I did there? Haha). There are many drugs that he might be on, so I won't assume he will speak pain. Sometimes just adrenaline is enough for a human to keep standing after getting shot. And I also don't believe in stopping power. Just in accuracy (brain or spine as switch off buttons), penetration, expansion that leads to higher wounding likelihood, the greater the wound, the faster one will bleed out. If the wound is in an artery or heart, better. What I mean is that I don't believe heavier bullet cartridges are any better against humans. As longs as they easily go through ribs, arms and skull, they are doing fine enough already. Defeating a bears' skull or ribcage is something completely different. Mass has to be retained after the initial contact with the bones. Humans' structure isn't as tough, therefore less mass is required to begin with. High pressure heavy pills such as .50 Beowulf, .458 SOCOM, .50 AE... These generate too much recoil for too few rounds in the magazine. My ability to put multiple rounds in the same 9 1/2 by 1/2" (human skull) target under a second will be significantly reduced. Not only that: I would need to reload in situations where I would still be left with 20 rounds in the gun if it was chambered in 300 BLK.

[Shushh]

Thanks for the reply and you're welcome. I'm a big 1911(2011) fan and with some of the new cartridge technology they can be darn potent. Nor are many of these rounds as wildcat as they used to be. Underwood for example is loading some darn hot 9x25 Dillon, 40 Super, 460 Rowland etc. I haven't done it yet but I'm thinking after the current 300blk project I'll do a 2011 in 40 Super.

Also of course to be clear, not putting down what you're up to, I'm on a 300blk forum after all. Right now I'm doing a 300blk build with similar goals. A suppressed pistol to make myself a more potent PDW then even the most extreme 1911 can be. But I ain't going 4.75" barrel short, I'm 8.5". 4.75 just sounds extreme to me to be prioritizing length so much but staying AR.

On grip size, totally get it, that turns me away from handguns like the desert eagle as well(among other things). Heck even the para style double stack 1911s I think are too big to be practical.

Sights, grips, a stock, etc. All valid points, and again why I'm doing it myself as well. Just get's to a point though that the gun is so much bigger in other ways that another inch or two in the barrel is almost inconsequential. It also puts it into the SBR category with the vertical fore grip. I don't know about specific laws where you are but it's a lot easier for the most part for it to legally be a pistol. Again, of course, your needs and all that, I'm staying legally pistol so I can lawfully travel with it loaded.

Magazines, sort of, there's no good pistol drum. But there are good stick magazines in the 26-33rd area for Glocks and 2011s(double stack 1911)

I'm curious where you got those velocity numbers, don't doubt them, just curious to look? Similarly is there a particular bullet you have in mind that is that light yet will do more then punch a hole at those speeds?

Suppressor under rail, I'm very new to suppressors, but personally I'm looking at not trying to fit it under the rail so I can get the Nomad 30. A shorter fatter can and thus make the gun shorter but with enough can to adequately quiet subs and not gas me. That Sig is as short, and if you're planning supersonic anyway, yeah I can see that. The Sandman K is even shorter at 5.4", they say it only adds 2.9" when put on over their muzzle brake. But it'd be even shorter direct mount. Maybe it's worthwhile to take an inch or two off the can and add it to the barrel, just a thought.

Drugged up bad guys in IIIA, wow that's a rare thing. Heck only one comes to mind, those LA bank robbers, there's probably more I'm just not aware, but can't be many. I can kinda see the need to plan for that if you're a personal security guy, run something like a jewelry store, or a pot shop. Damn didn't think of that till just now, a pot shop, HUGE security needs there. But then how important is concealment, I suppose if you want to hang it at your side under a jacket, I can see that. Again, not that you have to justify anything to anyone, just curious about the trade offs. Frankly for me, I'll come right out and say my biggest worry from a tactical standpoint is rogue out of control cops. Team blue has done some really bad things, it appears to be getting worse, and I want to be prepared for that. I drive truck and with incidents like everything from Reginold Denny to the Danziger Bridge murders, plus of course the regular risk of robbery, I feel the need to step up my game. Also hence the need to stay lawfully pistol for me.

Just my 2 cents and curiosities to meld into my own thoughts, later.

[Ghost12three]

Thanks for the reply and you're welcome. I'm a big 1911(2011) fan and with some of the new cartridge technology they can be darn potent. Nor are many of these rounds as wildcat as they used to be. Underwood for example is loading some darn hot 9x25 Dillon, 40 Super, 460 Rowland etc. I haven't done it yet but I'm thinking after the current 300blk project I'll do a 2011 in 40 Super.

Also of course to be clear, not putting down what you're up to, I'm on a 300blk forum after all. Right now I'm doing a 300blk build with similar goals. A suppressed pistol to make myself a more potent PDW then even the most extreme 1911 can be. But I ain't going 4.75" barrel short, I'm 8.5". 4.75 just sounds extreme to me to be prioritizing length so much but staying AR.

On grip size, totally get it, that turns me away from handguns like the desert eagle as well(among other things). Heck even the para style double stack 1911s I think are too big to be practical.

Sights, grips, a stock, etc. All valid points, and again why I'm doing it myself as well. Just get's to a point though that the gun is so much bigger in other ways that another inch or two in the barrel is almost inconsequential. It also puts it into the SBR category with the vertical fore grip. I don't know about specific laws where you are but it's a lot easier for the most part for it to legally be a pistol. Again, of course, your needs and all that, I'm staying legally pistol so I can lawfully travel with it loaded.

Magazines, sort of, there's no good pistol drum. But there are good stick magazines in the 26-33rd area for Glocks and 2011s(double stack 1911)

I'm curious where you got those velocity numbers, don't doubt them, just curious to look? Similarly is there a particular bullet you have in mind that is that light yet will do more then punch a hole at those speeds?

Suppressor under rail, I'm very new to suppressors, but personally I'm looking at not trying to fit it under the rail so I can get the Nomad 30. A shorter fatter can and thus make the gun shorter but with enough can to adequately quiet subs and not gas me. That Sig is as short, and if you're planning supersonic anyway, yeah I can see that. The Sandman K is even shorter at 5.4", they say it only adds 2.9" when put on over their muzzle brake. But it'd be even shorter direct mount. Maybe it's worthwhile to take an inch or two off the can and add it to the barrel, just a thought.

Drugged up bad guys in IIIA, wow that's a rare thing. Heck only one comes to mind, those LA bank robbers, there's probably more I'm just not aware, but can't be many. I can kinda see the need to plan for that if you're a personal security guy, run something like a jewelry store, or a pot shop. Damn didn't think of that till just now, a pot shop, HUGE security needs there. But then how important is concealment, I suppose if you want to hang it at your side under a jacket, I can see that. Again, not that you have to justify anything to anyone, just curious about the trade offs. Frankly for me, I'll come right out and say my biggest worry from a tactical standpoint is rogue out of control cops. Team blue has done some really bad things, it appears to be getting worse, and I want to be prepared for that. I drive truck and with incidents like everything from Reginold Denny to the Danziger Bridge murders, plus of course the regular risk of robbery, I feel the need to step up my game. Also hence the need to stay lawfully pistol for me.

Just my 2 cents and curiosities to meld into my own thoughts, later.

Here's where I got the velocity data:

https://loadoutroom.com/51926/ultra-sho ... up-part-2/

The SIG SRD762 can is just .1" longer than the Nomad 30, but I think that it is slightly better for being .11" thinner. That gives me more handguard options to choose from with the SRD762. I'm shooting supers only, in confined spaces, likely without ear pros on. That's why a full sized can is a must. I didn't go any longer because the ones I've found either had QD mounting systems and that does not like my under the handguard set-up, or had minimum barrel lenght restrictions greater than 4.75" or aren't as high quality as the suppressors made by AAC, SureFire, GEMTECH, and the like. Or they were so long that my overall length would be far from "MP5 maneuverable".

I think I should explain why I want to be able to penetrate body armor or take down a high on drugs adult male: an SR-25s in .308 or a 10.5" AR-15 in 5.56 can do both do it. If my rifle can RETAIN these rifle capabilities while not worrying about rifle weight and rifle length issues, then I have an ideal weapon. SMG maneuverable, rifle powered. I don't think I'll ever have a threat that is actually wearing any armor. Nor do I think that they would be high and wearing body armor at the same time. I just want to have this firepower because
1- why not?
2- because 2A
3- because America
4- Better to have it and not need it then need it and not have it (who knows... Maybe zombies?)

To sum things up, my initial goal was to build a reliable rifle that could be as effective as a 10.5" 5.56 AR-15 at close distances, in a package similar to that of an MP5. The pills are also heavier then 55gr or 77gr (the lighter ones showed problems in Iraq and African countries against high on opium or other stuff individuals that were shot 3-4 times in the belly and kept fighting until unconsciousness due to blood loss. Which gives one enough time to pull a trigger against you.) but the same as the SR25 ones.
The evaluation by SOCOM of the SIG Sauer MCX Rattler (5.5" 300 BLK) is an indication that this concept seems very welcome in CQC intended purposes.

And regarding legal aspects, I can make it a pistol by using a brace instead of a stock and a handstop instead of a VFG.

[Shushh]

And regarding legal aspects, I can make it a pistol by using a brace instead of a stock and a handstop instead of a VFG.

You know that's only true if it started life as a pistol and never became an SBR.

[Ghost12three]

And regarding legal aspects, I can make it a pistol by using a brace instead of a stock and a handstop instead of a VFG.

You know that's only true if it started life as a pistol and never became an SBR.

I have no plans of making this SBR to pistol "conversion" . I meant that on my parts list, it's as simple as a two-part swap of items and it becomes a pistol. When I get more into the legal terms and decide whether these laws you referred to apply to my state or not, I'll see if a pistol is gonna be the way to go. Thanks for the advice anyhow!

[Suputin221]

I can tell you that FMJ 150gr subsonic bullets will penetrate double thickness of level 2a kevlar. That is the projectile will easily pass through both sides of a 2a vest. I'm not sure how that would compare to a 3a but I suspect it would be a higher protection than 3a.

The 2a vest I have is 21 layers of kevlar on each side. Thus 42 layers of kevlar makes up both sides. The penetration capacity of subsonics is nothing short of incredible.

[DutchV]

bad guys dont wear body armor on their heads. #justsayin

This. Headshots for the win.

Also, a Gen 3 Glock plus an adapter from Endo Tactical and a KAK arm brace makes a very small package for a pseudo PCC. Add a red dot and you're in business.

[plant.one]

Barnes Tac-TX 110gr:
4.75" Average 1846 fps, SD 6

(from hornady ballistic calc)




10mm (from the wikipedia page)








i'll take 30 the round mags and the reliability, handleability and functionality of an ar-platform PDW style pistol over a 10mm glock - or 1911, or DE - any day of the week.

with barnes blacktips at the speeds the OP is showing... hands down.



ok you got me, i'm biased... and i built mine on a 9" barrel. but whatever