"Ideal" 9mm bbl length?

[michael_aos]

With regard to handgun ammo, is there an "ideal" 9mm AR barrel length?

I've been really drawn to the idea of SBR'ing my Olympic K9GL. I just kind of assumed I'd go 8", but now that I Look at it, 7" might be better.

I'm figuring 8" is roughly 91% the velocity of 16"
Figuring 7.5" is roughly 90% of the velocity of 16"
And figuring 7" is roughly 88% the velocity of 16"

I don't really have any idea what an inch of barrel weighs.

The point of the exercise is to move the balance rearward, reduce weight, and just generally make it a little more handy.

Mike

[Hoser]

The point of the exercise is to move the balance rearward, reduce weight, and just generally make it a little more handy.

Mike
An A1 buttstock with a little lead in it will accomplish the same thing. Much cheaper but lower on the CDI scale.

If I had more $$$ than I needed, I would go no shorter than 10.5 without a can. Stick a can on there like an SD and that would be cool.

[michael_aos]

Much cheaper but lower on the CDI scale.

I admit I'm going for a CDI factor.

Mike

[bluker1]

I run the barrels for FA 9's at 10inches. That is mainly so I can put the suppressors on.

alan[/i]

[michael_aos]

I'd definitely like a "suppressor friendly" configuration.

What is it about 10" that allows it to accommodate the silencer?

Mike

[bluker1]

I'd definitely like a "silencer friendly" configuration.

What is it about 10" that allows it to accommodate the silencer?

Mike

It it is much longer the suppressor on the end feels very heavy. It is just a personal preference.

alan

[michael_aos]

So, say, a 7.5" bbl wouldn't necessarily prohibit installing a suppressor?

Mike

[bluker1]

So, say, a 7.5" bbl wouldn't necessarily prohibit installing a suppressor?

Mike

nope. It would just have to be on registered SBR, Pistol upper, or an MG.

alan

[Spetsnaz]

Sweet 9mm supressed upper

http://img29.imageshack.us/img29/8841/12508pic31on.jpg

Colt slide in mag block
RRA A3 upper
TROS 3 lug 5" barrel
RRA bolt group
KAC FF RAS
modified Troy sights
Aimpoint M2 in a Larue mount
Gemtech Trinity w/3 lug

[PsychoI3oy]

A rifle in a pistol caliber with a 5" barrel is better than a pistol how?

Ok, that may sound a bit snide, but wouldn't the ballistics be the same? I'm sure the sight and sight radius and stock help with accuracy, and I'm sure it looks darn cool but to go that route it makes more sense to have a rifle in a rifle caliber and a handgun in 9mm.

Then again I don't own an AR in any caliber so these are likely just n00b comments.

[MPfiveengineer]

A rifle in a pistol caliber with a 5" barrel is better than a pistol how?
.

Greater controllability and rate of accurate fire. If you are looking to suppress it I would go with the TROS 5in barrel. The problem with anything longer is keeping a 147grain bullet subsonic, especially at altitude.

As far as ballistics go I like 8.875in, but I am an MP5 guy :mrgreen: . A friend and I did some testing on .75" Plexiglas with a G17 and a MP5, both using WWB 115gr at about 10 yards. The G17 did not penetrate with 3 rounds while the MP5 went through it every time

[2ndChildhood]

Greater controllability and rate of accurate fire. If you are looking to suppress it I would go with the TROS 5in barrel. The problem with anything longer is keeping a 147grain bullet subsonic, especially at altitude.

As far as ballistics go I like 8.875in, but I am an MP5 guy :mrgreen: . A friend and I did some testing on .75" Plexiglas with a G17 and a MP5, both using WWB 115gr at about 10 yards. The G17 did not penetrate with 3 rounds while the MP5 went through it every time

Ok, noob questions here;
If it's the same round, what is the difference? Is the longer barrel on the MP5 getting more velocity out of the round or stabilizing better or what?
What's the deal with "keeping a bullet subsonic"?
Thanks, 2C

[MPfiveengineer]

Ok, noob questions here;
If it's the same round, what is the difference? Is the longer barrel on the MP5 getting more velocity out of the round or stabilizing better or what?


More velocity, kinetic energy = 1/2 (mass)(velocity)^2




What's the deal with "keeping a bullet subsonic"?


When shooting with a silencer you need the bullet to stay subsonic so that it does not make a sonic crack when it comes out of the silencer.