how much velocity do common pistol cartridges (9mm, .40, .45) gain in a carbine-length barrel?  at what point does the increasing velocity from increasing barrel length become negligible? (for the purposes of this question, let's not worry about the 16" NFA rule).

also, does the added length of a suppressor increase velocity as if it were part of the barrel?

finally, is it true that you're not supposed to use hollow-points in a suppressed firearm?  i read this somewhere.

before all the legal eagles chime in, i realize i'm in an NFA-unfriendly state, i'm just asking for curiosity's sake.

NONE!

Pistols are for use as toys and plinking guns, or to club yourself for putting down the rifle that you wish you had now. Pistol caliber carbines are nothing more that long barrel pistols which only bounce off of badguys and loaves of bread!

You cannot expect to survive any type of defensive confrontation if you have anything other than an AR-15 in 5.56 and the barrel cannot be any shorter than 16" and you must be using only approved ammunition (there is a list of approved ammunition in the ammnition forum).

These facts have been proven multiple times by shooting ballistic jello and split top wheat bread. For this reason the hivemind has adopted this philosophy. Now, go and flog yourself for thinking otherwise.

I don't have any figures on hand, but the velocity is increased in minor amounts with the additon of a longer barrel. It simply gives the powder charge more time to get the projectile moving. The gains are not however, massive.

A suppressor is made to be used with sub-sonic ammunition. meaning that the projectile does not break the speed of sound in flight, causing a mini-sonic boom. You do not want a high velocity round with a suppressor.

NONE! Pistols are for use as toys and plinking guns, or to club yourself for putting down the rifle that you wish you had now. Pistol caliber carbines are nothing more that long barrel pistols which only bounce off of badguys and loaves of bread! You cannot expect to survive any type of defensive confrontation if you have anything other than an AR-15 in 5.56 and the barrel cannot be any shorter than 16" and you must be using only approved ammunition (there is a list of approved ammunition in the ammnition forum). These facts have been proven multiple times by shooting ballistic jello and split top wheat bread. For this reason the hivemind has adopted this philosophy. Now, go and flog yourself for thinking otherwise.

 

this is what i get for posting this thread in GD instead of the armory or the ammo forums.

Quoted: I don't have any figures on hand, but the velocity is increased in minor amounts with the additon of a longer barrel. It simply gives the powder charge more time to get the projectile moving. The gains are not however, massive. A suppressor is made to be used with sub-sonic ammunition. meaning that the projectile does not break the speed of sound in flight, causing a mini-sonic boom. You do not want a high velocity round with a suppressor.

i know that it won't be very quiet, but it wouldn't actually damage the suppressor?

and, IIRC, most .45 is subsonic.  i guess what i'm trying for here is to get the most velocity out of a .45 shot from a carbine while still having the round remain subsonic so the suppressor can be as effective as possible.

Quoted: Quoted: I don't have any figures on hand, but the velocity is increased in minor amounts with the additon of a longer barrel. It simply gives the powder charge more time to get the projectile moving. The gains are not however, massive. A suppressor is made to be used with sub-sonic ammunition. meaning that the projectile does not break the speed of sound in flight, causing a mini-sonic boom. You do not want a high velocity round with a suppressor. i know that it won't be very quiet, but it wouldn't actually damage the suppressor? and, IIRC, most .45 is subsonic.  i guess what i'm trying for here is to get the most velocity out of a .45 shot from a carbine while still having the round remain subsonic so the suppressor can be as effective as possible.

Why are you interested in a supressor? The sound of an AR-15 being discharged is inaudible.

Normal factory pistol loadings end up getting the best velocity out of a 9-10" barrel.

Now I have talked to a guy that wanted to get performance loads worked up for a 9mm AR. In IPSC, we shoot 9mm's loaded wayyyyy up. usually a 124gr. going 1400 fps. Using a really slow powder, which really works well in a rifle. Somewhere around 8+ grs. of true blue will get you 1900fps out of a 16" AR.

*Careful with these loads, use at own risk!*