Perfect SBR length

[interceptor]

Hypothetically speaking, if a guy was going to cut down an AR barrel and do a SBR, about what length would be desireable? Then end result would be something I would want to use for out to 100 yards, subsonic with the can.

I see some others that are about 10.5" here on the board, but want some imput as to how those guys feel about them, if they would have gone longer or shorter if they had it to do over again.

[amafrank]

While I can't speak for the AR crowd I can say that my SIG 552-300 with a 9" barrel is quite nice. I'm not sure how much difference the barrel length will make if you do your own loading. You can tailor the load to fit the barrel length by using faster powders for shorter barrels. The most likely way to figure out whats best is to see what sort of accessories and handguards you will have and fit the barrel to them. . .

Frank

[LouBoyd]

Hi. I'm new to this forum but have been experimenting with subsonics in various rifles and assembling asorted calibers of AR-15 for several years. Recenetly M1S shipped me a custom 300-221 (300 fireball chamber) 10" long, 1-8 twist pistol barrel with a standard pistol gas port location. After running Quickload calculations I had concluded that was close to ideal for 200-240 grain bullets at 1000 fps muzzle velocity and still cycle an AR-15 action. For most reasonable propellants with uncoated or moly coated 200 to 240 grain jacketed bullets in a 300-221 bullet velocity peaks between an 8" and 10" barrel length requiring more propellent for a shorter or longer barrel. I chose 10" since I can cut it down more if I want but can't extend it. Having a barrel longer than where the bullet achieves peak velocity does allow more expansion and less muzzle blast, but it can't help velocity consistancy due to bore friction and that has to hurt long range accuracy from vertical stringing. Shorter would give more muzzle blast and makes it more difficult to time and cycle the action with no other benefit than being short.

I can't say I'm an expert. This is my first 300-221 build. I have an MIS 16"1-8 Fireball carbine which shoots pretty well with Corbon 220 gn subsonics. The Corbon ammo appears to be designed for a 16" carbine. . The pistol is still under construction so I can't prove any of the above even to myself. I expect it though to give a little better accuracy than the 16" barrrel using lighter loads and still cycle an AR-15 action ok. I wouild not expect a 10" or shorter barrel to give as good of performcane as a 16" with lighter supersonic bullets.

[Ron458]

I love my 10.5 but like amafrank said. Whatever works best for you. A subsonic 220-240g bullet dosent require much brl. I did a 9" brl for someone the other day. It worked best with his freefloat & supressor.

[interceptor]

What kind of effective range should an owner expect from a 9"-10" barrel with heavy subsonics and a supressor? I'm looking for 100 yards on in, but after that would be a bonus as far as I am concerned.

[Ron458]

Its subsonic no matter what the brl length is. The post below(max range 300W) should answer your Q.