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Old 04-18-2019, 08:51 AM   #1
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9mm ammo choice for SBR-length barrels

Looking for opinions on defensive ammo choices for a 9mm with a typical SBR barrel length; from 7-10 inches or so.

I've been a fan of pistol-caliber carbines for a long time and have shot a lot of loads thru them as well as thru normal handguns, but never owned a pistol-caliber gun with a barrel length in between the two. Things like the Evo Scorpion, MP5 pistols, etc, are getting more & more popular nowadays and I have almost no first-hand experience with them. I have a 9mm AR pistol on order with an 8.5" barrel, and am curious for thoughts & experiences on ammo for these mid-length barrels.

Just to get it out of the way early, this is NOT intended to be my primary defensive gun or anything; that is and will continue to be 5.56 AR and 9mm glock. It will probably be a mostly playing-around gun. But still curious about the 'what if' aspect of things.

Since with handgun loads the increased velocity of longer barrels tend to lead to more expansion and less penetration, we have to be careful of over-driving bullets to a velocity that actually hurts their performance. In my small edc pistol, I carry a lightish, +P round; and that could be a bad choice for this substantially longer barrel.

I'm thinking the 124-grain XTP +P might be a good potential candidate. XTP's tend to be on the less-expanding, more-penetrating side of things to begin with, the longer-than-normal barrel length may nudge it toward more expansion, and the +P version may help even more.


So, the point of this thread: regardless of how people feel about the whole pistol-caliber carbine or pistol-caliber AR concept, a simple question:

If you HAD to use a 9mm SBR with an 8-10 inch barrel for serious purposes, what ammo would you load it with?
 
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Old 04-22-2019, 09:43 AM   #2
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Tried out the AR9 pistol from ABC rifles. Not a ton, just four boxes of assorted rounds from 115 to 158 grain. Didnít chrono anything or do any terminal testing, just zeroing the red dot and some function testing the gun.

First, function was almost 100%. There was only one bobble, and that was with Fiocchi 158-grain FMJ, a failure to feed on the first round from the mag. It may have been a fault of the bullet profile (doubtful), or an issue with me releasing the charging handle (possible), or just an issue with the gun being new and unbroken-in (likely). But other than that, feeding & functioning was fine with 115-grain fmj, 115-grain UMC JHP, 147-grain fmj-fp, and 158-grain fmj.

My experience with 9mm ARís is very limited, owning only one before this; a JRC 9mm takedown carbine. I one time rented a 9mm smg at a range when my sons were younger to let them try one, but other than that have very little experience with a 9mm Ďcarbineí based on the AR other than the JRC. Being a blowback action, the bolts on most 9mm ARís are inherently heavier than a normal AR, so they tend to have a heavy Ďslammingí to the recoil impulse rather than the light & fast cycling of a typical rifle-caliber AR. And this little gun is very bad with it, partly due to the nature of blowback 9mm ARís as a species, and partly due to their choice of brace used. It has a KAK Shockwave Blade brace which has a very thin (like ľĒ thin) back edge on it, so the recoil is concentrated in that one narrow space. Iím not overly recoil sensitive, but before I got to a hundred rounds it was very noticeable. If I catch a deal on an SB brace, I may swap it out. I swapped a Shockwave Blade to an SB on a .300BK pistol build (putting the Shockwave on a rimfire gun), and it was much more comfortable. I suspect with the blowback gun the improvement would be very significant, making it simply more comfortable & fun to shoot.

Regardless, neither the JRC 9mm or my old Camp-9 have a felt recoil anywhere near this noticeable. Being that theyíre all blowback 9mmís, I suspect the Blade brace is a big part of the equation; and of course this one being the lightest of the three also contributes to it. I may or may not look into ways to reduce it; possibly a lighter bolt & heavier spring; I havenít checked into it and donít know much about them yet.

I completely understand that I sound like a big wuss, talking about the recoil of a 9mm, but configured the way it is, itís a very real thing. Next trip out, I may try simply swapping lowers between it and the .300 pistol (with the SB brace) and see if that makes a difference. I just didnít have it on hand yesterday.

Pansy-sounding recoil issues aside, the main functional negative on the gun is tightness of the magwell. I used glock factory 10- and 15-round magazines, and ETS 15- and 31-round magazines, and none of them came even close to dropping free. Donít know that thatíll be a big enough issue to be worth loosening it up or not. The fact that the gun has no bolt hold-open kind of makes that a moot point to some degree; since reloads arenít going to be particularly fast anyway.

This gun has a 1/2x36 thread pitch on the barrel and all I have are 1/2x28 and 5/8x24 suppressor adapters, so I couldnít use the suppressor. The adapter is supposed to be here soon and once I can attach the suppressor itíll make it easy to see which loads (if any) remain subsonic thru an 8.5Ē barrel.

Anyway, new-gun foibles and quirks being unavoidable to some degree, itís still a fun gun. Mostly just shot a twigs & crap floating in the pond, and Ďso far so goodí at this point.
 
Old 04-25-2019, 05:15 AM   #3
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Since taking this pic and firing it for the first time, I've shortened the brace another notch or two. It came with the fold-down sights, and I added a Sparc-AR I had on hand. I have a used MRO that I was planning to put on it, but on this size gun it was awkwardly large. Even the Sparc-AR seems a little large on it.

The rear sight wasn't originally that far forward; I moved it to where it is in order to clear the charging handle better. The magazine is a 15-round G19 mag:
 
 
Old 04-27-2019, 08:16 AM   #4
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cute!
 
Old 04-28-2019, 08:56 PM   #5
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are you gonna put a can on it? Will it feed 158 gr lhps? if the answers are yes, you wnat whatever load gets you 1000 fps with that bullet. Otherwise, I'd say plus P 115 gr jhp's, probably Corbons, but no real experience on my part. You'd want them going 1500+ fps if you're not going to have a can on it. The extra 4" of barrel can get that for you, as vs handgun velocities with that same ammo. POI might be quite a bit off from typical practice ammo, tho. Might have to load your own ball bullets to get that achieved. I dont see any reason to bother with it, other than for the sort of person who want practice enough, wont carry. For those, the answer is a used Hi point 9mm carbine, with a laser sight.
 
Old 04-28-2019, 09:00 PM   #6
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for people who might actually be able to amount to a hoot in their own defense, it's the pistol for normal times and the silenced AR with 60 gr 223 softpoints for shtf sorts of stuff. Putting on the armor first is more important for a home defense thing than getting the longarm instead of just drawing the pistol. They take the same amount of time and the armor is far more likely to save you, than taking the time to run and get the longarm (as vs just running them off with the pistol)
 
Old 04-29-2019, 05:32 AM   #7
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Quote:
Originally Posted by boati View Post
are you gonna put a can on it? Will it feed 158 gr lhps? if the answers are yes, you wnat whatever load gets you 1000 fps with that bullet. Otherwise, I'd say plus P 115 gr jhp's, probably Corbons, but no real experience on my part. You'd want them going 1500+ fps if you're not going to have a can on it. The extra 4" of barrel can get that for you, as vs handgun velocities with that same ammo. POI might be quite a bit off from typical practice ammo, tho. Might have to load your own ball bullets to get that achieved. I dont see any reason to bother with it, other than for the sort of person who want practice enough, wont carry. For those, the answer is a used Hi point 9mm carbine, with a laser sight.
So far, other than one round failing to feed when brand new, it's fed everything I've tried in it from 100 to 158 grains. I swapped the Mystic-X suppressor to it (from the .22 rimfire) and ran it some more yesterday. It kept all the 147's and 158's I ran thru it subsonic; I wasn't sure if 147's would be, but they are. Through the Camp-9 some 147's are and some aren't, so wasn't sure how they'd do thru this 'in-between' length barrel.
 
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