4.5" .223 AR Upper

[Jayhawker]

Bear Creek Arsenal has a complete 4 1/2" AR pistol upper for $250 ish...It's cute but I can't help but wonder about the efficacy of such a thing...Discuss

[Elk Creek]

WHAT? I CANT HEAR YOU! I Shot a 4.5 INCH 556 AND LOST THE LAST OF MY HEARING, AND EYEBROWS……

[CPJ 2.0]

“Hey Rocky! Watch me turn a .223 into a .22 LR! “

[Freezer]

I had a 10.5 inch and it was a blast to shoot. I gave it to my son because every time I took it out it cost me $100.
I'll stay with my 22s.

[Chiro1989]

Not even sure if 4.5” is enough barrel to stabilize a 55 gr bullet

[PFD45]

Can I get one in .308?

[bullsi1911]

That would be a good way to clear out an indoor range

[Jayhawker]

I have an 8.5" upper on my current house/truck gun...it's loud and quite the little flamethrower...but it remains minute of bad guy accurate...Can't help but think that anything shorter in 5.56 would be nothing more than a bullet hose...

[Jay]

One of my buddies built an SBR in 5.56 with a 7.5” barrel. Legally, of course We chronographed it. Pretty much 22 mag ballistics. It’s nothing but a loud, flame throwing toy.

The blast and flash with a short barreled rifle round tells you what you need to know. Most of the powder is burning outside the gun.

[Freezer]

Could a hand loader change that blast and flash by switching powders? Say to a pistol powder? Is there load data for SBRs?

[GrapeApe]

I checked with Quickload. My 10.5" pistol load using H322 should burn approximately 70% of the powder in a 4.5" That's with hornady 75gr "SBR" bullet seconds. Dropping down to 50-55gr bullets, even with H322, which is a relatively fast rifle powder, it drops closer to 50% burn.

Also, projected MUZZLE pressure is over 38,000 PSI. Most of the 22 cal silencers I've seen that list a minimum barrel length, say 10", so it wouldn't be safe to even put a silencer on it to help with the blast