Barrel length effect on 9mm velocity 3" vs 3.5" vs 4"

[wb_carpenter]

Just as the title says I am trying to work up some 9mm minor loads and most are loaded through a 4in barrel and I have a 3.5". I know there will be a difference I just don't have a clue how much(couldn't find much chrono data online).

[fecmech]

WW white box ammo had approx 100 fps increase between a 3.5" Khar and a 4.7" Browning HP that I owned.

[Bret4207]

Well, it's going to depend on the powder type and pressure curve. Everyone uses 50-75 fps per inch but you won't know with out testing it yourself in your gun with your loads. I found most of those 1300 fps 9mm+P loads of the 80's gave more like 1100 fps. Chronos can be a real let down for advertised specs!

[Catshooter]

wb,

A half inch isn't much. You could well find that the 3.5 is faster than the 4.0, it's happened to me.

So the answer to your question is probably not much, anywhere from zero to 125 fps or so.

Only way to know is measure.


Cat

[9.3X62AL]

SIG P-226 (4.4" barrel) runs Speer 124 grain +P @ 1225-1250 FPS.

SIG P-228 (3.9" barrel) runs these same loads 1190-1215 FPS.

These loads pretty much duplicate the M-9 service load's external ballistics, but do so with a controlled-expansion bullet. I haven't run these through a 5" barrel like that found in a 1911A1 or Beretta 92, though.

[thegreatdane]

http://www.ballisticsbytheinch.com/ <- Great info.

[GabbyM]

My Taurus M92 with 5" barrel would shoot the same loads over a chrony slower than my S&W M659 with 4" barrel. Probably due to oversized bore in the Taurus. M92 was slower with J bullets or .356” cast loads. Shot the same day from same box of ammo.

In addition to the velocity disappointment the Taurus was less than accurate. It’s not here anymore.