9mm barrel length / velocity

[voilsb]

Does anyone know what barrel length would yield maximum velocity with a 9mm? Obviously, this would depend on the bullet and powder used, but perhaps a ballpark range? For instance, what barrel length maximizes velocity out of WWB? 147gr SXTs?

I understand the 9mm isn't helped much by longer barrels, but where does it drop off? Does a 10" barrel give a significant boost over a 5" barrel? Does 7.5"? Anyone have chrony data for a 9mm out of a carbine and a pistol?

 

[grendelbane]

I don't have my records handy, but my memory is like a steel trap. (Gets rusty quick).

As I recall, my AR-15 9mm with the 16" barrel will pick up circa 200 fps with most 115 grain loads. That is compared to my SIG P226.

Heavier bullets gain a little less, lighter bullets gain a little more. This is because the increase is in kinetic energy, which goes up by the square of the velocity.

I can't tell you where a 9mm velocity maxes out. My 16" barrel will give higher velolicities than any pistol I have ever chronoed. My shooting buddy has both an M16 with a 10" barrel, and an Uzi with whatever length barrel they have. One day I will get him to shoot over my chronograph. I suspect that there will be only a small gain in the 16" over the 10".

9mm carbines are nice. Basically, they provide > .38 Super ballistics, which isn't bad. My chronograph can not tell the difference between my AR-15 with 125 grain +p 9mm and my SIG P129 with 125 grain 357 SIG. Of course, there is a >12" difference in barrel length!

 

[voilsb]

Neat, thanks for the info! That's kinda what I suspected, but I don't have any experience with anything bigger than a pistol in 9mm.