SBR loads

[skizzums]

hey guys, i would like to get some opinions, maybe even FACTS, from the gallery here. We all know AR pistols in .223 suck, right? the beauty of 223 is in it's high velocity to create devastating wound channels, and without that velocity, we are essentially just shoting a 22. well, i have a pistol in 300BLK, my wife likes the gun, but not the caliber. i am building her one in 223 and have finishe it except for the barrel. the purpose of the gun is her HD carbine, or whatever you want to call it. before i go buy an 8" barrel, i was looking at different bullets and thinking the short barrel might not be too bad with the right bullet. i am seeing bullets like 35gr Tipped HPs from nosler, 40gr Blitz kings and HPs from sierra and 40gr SP from speer. i am not sure, but i think i would be able to get to velocities that would encourage expansion/tumble at those weights with proper powder selection. the fastest .223 powder i have used is h335, after a look at the burn chart, i am thinking i might need some reloader 10x, h322 or 4198.

sorry so lengthy, but what do you think i can get velocity wise from a short barrel using tiny bullets and fast powder? what bullets would you recommend? what powders should i be looking for? is it possible to get into the upper 2000's from an 8-9" barrel?

thanks for any suggestions, if my dream isn't possible, i will be willing to move up to a 10" barrel if needed, but would really rather not; but i also don't want a rifle that is unable to properly utilize it's cartridge.

[jmorris]

I have a pretty mild 223 load using TAC and a 55 gr that is still over 2500 fps out of a 10.5" barrel. I think 2000 should be no problem, wouldn't be my first pick for SD but that's a different matter.

[Brian Pfleuger]

Originally Posted by skizzums

sorry so lengthy, but what do you think i can get velocity wise from a short barrel using tiny bullets and fast powder? what bullets would you recommend? what powders should i be looking for? is it possible to get into the upper 2000's from an 8-9" barrel?

thanks for any suggestions, if my dream isn't possible, i will be willing to move up to a 10" barrel if needed, but would really rather not; but i also don't want a rifle that is unable to properly utilize it's cartridge.

I'll get my objections out of the way first, ok.

1)A .223 with an 8" (or 10") barrel is going to be GOD AWFUL loud. In the unfortunate event that it's ever needed for defense and the defender doesn't don hearing protection, you can bet your house they'll have permanent hearing damage. Yes, better than being dead. No, not the best better than being dead.

2)A .223 with an 8" barrel will never "properly utilize" the cartridge. I can run the numbers in QuickLoad for you (8 or 9EST tonight) if no one else does but there are much better options. I'd much rather have a Kel-Tec PM30, for example.

Now to your specific questions on bullets and powder.

Generally speaking, the powder that produces the fastest speed in a longer barrel will also produce the fastest speed in a shorter barrel. However, this length is getting into the extremes where that generality is no longer true and even at lengths when still true that speed comes with a price... see objection 1... severe muzzle blast.

An ordinary rifle (barrels of 20"+) will have muzzle pressures somewhere usually under 10,000 psi and sometimes as low as 5 or 6,000. A rifle cartridge fired in a 15" barrel can easily have muzzle pressures up above 15 or even 18,000psi. A .223 fired in an 8" barrel would be at least that high, I would guess, and maybe higher. The blast, especially in an enclosed space is going to be horrendous.

You can easily get 2,000 in a 8" barrel. I doubt 2,500 would be a problem. I'd be looking to trade speed for less muzzle blast though. I'd rather have 2,000 or 2,200 and 8,000psi than 2,500 and 15,000.

Only QuickLoad can really tell you though.

[mdmtj]

If you look at the forums that talk AR SBR/pistols, you'll see that a lot of folks will say 8" with the .223 is too short - Loud, muzzle flash, difficulty getting gun to cycle properly, muzzle velocity,... But you'll also see the folks that say "mine runs fine with no problems". I'm in the process of building a .223 pistol. Based on what I've seen and read, I won't be going shorter than a 10.5" barrel. There are muzzle devices that will greatly reduce the flash and direct the blast away from the shooter. I'm more interested in a truck gun and my state defines a pistol as <12". Building as a pistol allows me to carry it loaded in the vehicle with my CCW.

[burninghXcsoul]

Why doesn't she like the .300 blkout? The beauty of that round is it is meant to burn all of its powder in a pistol length barrel. What loads were you using? Were supers too much for her or subs?

I cast the lee 230gr bullet and sub with 12.1 grs of IMR4198. Its a very low recoil round thats not too bad to fire.

[Jim243]

I think that 10.5 inch barrel is the min I would use. Equipped with a Sig SB-15 brace it would be a very effective HD for her to use.

http://www.sigsauerguns.com/product-...ilizing-brace/

Jim

[skizzums]

She is also fine with the 230gr lee loads, but a subsonic 300blk is no better than a magnum pistol, kind of defeats the purpose is a rifle imo. Likely this rifle will never be deployed anyways and be shot at the range often, but still would like to know some stats of the tiny hypersonic bullets out of a sbr length. Let's take the HD out of the scenario, and figure out what would be the most potent bullet for reason of just knowing. I have never used the sub 40gr bullets, I don't know if the bullet construction calls for a speed unachievable without a rifle length barrel, or if I should go the opposite route of "bigger is better" and pump 80grainers through it. I would really like to know about different bullets, the construction, the demands and what's realistic from this platform. So if we take the perrp out of the picture and swap it with a deer, what would be the best load?

[Brian Pfleuger]

Light bullets can be moved pretty fast but they lack Kinetic Energy, in this scenario. Heavy bullets move slower but tend to have more Kinetic Energy. Bullets need only one thing if they are to expand.... Kinetic Energy. If you look at Hodgdon's data for .223Rem pistols, their 70gr max load makes 968 ft-lbs while their max 36gr load makes 843 ft-lbs. That's a difference of 15% more KE and 50% more momentum both in favor of the 70gr. That means better expansion and better penetration. It might not penetrate a lot more (or even could be the same) because it will expand more but in a relative sense both will be better.

If you're shooting at large (non-varmint) living things, you need a bullet that will expand but not fragment. Most light bullets are designed to fragment because they're made for little critters.

In other words, if it were me (I'd go no shorter than the 10.5" barrel), I'd use heavier, big-game type bullets and a variety that was on the lower end of strength so as to insure expansion at the relatively low speeds. I've never tried to know that particular combination so I can't say what bullet that would be.

[jmorris]

1)A .223 with an 8" (or 10") barrel is going to be GOD AWFUL loud. In the unfortunate event that it's ever needed for defense and the defender doesn't don hearing protection, you can bet your house they'll have permanent hearing damage. Yes, better than being dead. No, not the best better than being dead.

Mine is a 10.5 about the same length as a 16" with the suppressor mounted. Makes for a rifle that I can grab quickly without having to don hearing protection.

It's for a different use that is not as cool as CQB or SD though but I bet it would still work.