158 Gr. 38 Spec. From 4", 5" & 6" barrels

[K Harris]

Out of curiosity, has anyone here personally tested commercially available 158 grain loads (both standard pressure and +P) over a chronograph, from Model 10's with 4", 5" & 6" barrels? I would be most interested in the 158 grain lead semi-wadcutter.

 

[pps]

I think B/C gap and variability from each individual gun will factor in more than an inch of barrel length.

for eg: my 4" ruger .357 consistently chronographs 50-100fps faster than my 5" barrel 627.

 

[handgunner356]

Usually you can guess 25-50fps faster per inch but like said there are other factors. B/C gap probably has some of the biggest effect on velocity. The hotter loads will get better gains as the barrel length increases and fall off faster in the shorter barrels. I have one 3" .357 magnum that will match my 6" gun with most loads in 38 & 357, but there are a few with the way they are loaded that can split 100fps between guns.

 

[OKFC05]

From running the chronograph at IDPA matches, I recall that no commercial 158gr standard .38 has ever made power factor (125) in a 4 inch barrel. Some of the +Ps do not quite make it either. (Power factor is bullet weight times MV div by 1000). There is a large variability between guns and brands of ammo.

Basically, until you run your gun with a specific load over the chrono, you're just guessing what you might get.

 

[flop-shank]

for eg: my 4" ruger .357 consistently chronographs 50-100fps faster than my 5" barrel 627.

That's not surprising. Rugers tend to shoot fast.