"Ideal" 9mm bbl length?

[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.