Barrel length for suppressed .45 ACP carbine?

[Derek Zeanah]

So, I just picked up a .45 carbine that seems to be pushing standard 230gr target ammo to supersonic speeds through its 16" barrel. Which is fine, because the goal here was to cut the barrel back to something pretty short anyway once I get permission to do so.

The question is "how short?"

So, the plan being to keep the suppressor on it full-time and keep full-power commercial ammunition subsonic, what barrel length is about optimal? Or, how long is too long, or something.

Thanks.

(It's still reasonably quiet suppressed right now - the ring of steel from 50 yards is louder than the sound of the round being fired - but it's still got a bit of "crack" to it.)

 

[Phaedrus/69]

Just out of curiosity what did you get? I just sent my info to the attny to set up my trust, so pretty soon I'll efiling my Form 1 to cut down my HK USC as part of the UMP conversion. IIRC the stock UMP barrel is around 8.5". Seems like all subguns run around 8" to 9".

 

[Derek Zeanah]

I just went with a Just Right carbine. Not nearly as cool as an HK, but I like the simplicity (and price).

A big part of that decision was my local gunsmith. JR told him his couldn't be converted to 10mm, so he did it anyway and it's gone ~ 2,500 rounds without issue. It's hard to argue with that.

 

[Surly]

A big part of that decision was my local gunsmith. JR told him his couldn't be converted to 10mm, so he did it anyway and it's gone ~ 2,500 rounds without issue. It's hard to argue with that.

A little OT, but I love it when they say it can't be done and I do it anyway. LMAO!

 

[Derek Zeanah]

Well, having a gunsmith with an engineering degree helps as well.

 

[Phaedrus/69]

I think those JR carbines look pretty neat! And while I love my HK USC I couldn't in good conscience recommend one to anyone that's not a rabid HK fanboy (like me!). It's really expensive and not all that tacticool until you drop another $1000 to do an UMP conversion. If I had it to do all over again I suppose I still would but it would probably have been smarter to get a JR or a Thureon Defense. The Beretta Storm carbine is really nice (I have one in 9mm) but the .45 ACP version is limited to 8 round mags and was just discontinued.

Length-wise I think one thing to look at is the form factor of the gun. Your JR, like my USC, is laid out like a rifle with the magazine in front of the trigger. The Beretta Storm is laid out like a big pistol, with the mag feeding up through the grip. So even with the full length 16" barrel my Storm is only 30.5" long. I could cut my USC back to maybe 10" and it would still be longer than my Storm.

But I think 8-9" is kind of the sweet spot for .45 ACP.

 

[HRnightmare]

I also believe anything over 8-9" starts to slow the .45 ACP down vs speed it up. I have documentation at home about the right length. I was planning on doing a KRISS rifle and getting it SBR approved.

 

[OilyPablo]

I would agree around 9"-12" is sort of a sweet spot but it really depends on bullet weight. None slow down until 18" or so. And lighter bullets are still accelerating at 16".

 

[wally]

"Ballistics by the inch" might be a good starting point:

http://www.ballisticsbytheinch.com/45auto.html


If its always going to be suppressed I'd just go with 4-6" barrel to keep the OAL down when the can is attached.