Winchester AutoComp Powder in .44 mag interesting results

[10mmShooter]

Hey Guys testing some Winchester AutoComp powder on the Chrony today and interesting results in .44mag vs WW231 and HP 38. I loaded my 240gr LRNFP in my Henry 20 inch barrell sized .432

8.0 grs of AutoComp 1149 fps 10 sd 39 es (vintage 2014) max 11.5 grs
8.1 grs of WW 231 1201 fps 8 sd 37 es (2009 vintage) max 11.0 grs
8.1 grs of HP 38 1174 fps 10 sd 44 es (vintage 2014) max 11.0 grs

Do you see the oddity. WW231/HP38 are relatively fast pistol powders. AutoComp is listed at medium burn-range pistol powder, close to AA#5 and SR-4756 on the burn chart.

Given that the max loads for.44 mag are close at 11-11.5 grains. How is it that the faster HP38/231 generates move velocity than AutoComp, a slower burner.(actually given the .1 gr difference in loads tested the velocities are effectively the same) Keep in mind we are shooting same brass/same primer out of a 20 inch rifle barrell. Plenty of barrell for maximum powder burn.

I was hoping due to its postion on burn charts that AutoComp could keep up with AA#5 and SR-4756 loads in the medium burn pistol powder. Not going to happen, AutoComp can only keep up with HP38/231. AutoComp doesnt have the legs to keep up with AA#5 and SR-4756 in velocity.

So I dont really see a place in my stable for Winchester Auto Comp, even in my 10mm, SR4756 and AA#5 and AA#7, HP38.231 are better powders and seem to do more.

thought sanyone ?

[Grump]

Was searching for others' experiences with AutoComp in revolver loads and found this one. So, back from the dead.

I think that something is out of whack with the official Winchester data. My experience in 9mm was that it launches the bullets just about as fast as advertised.

.357 Mag is another situation altogether. EVERY indicator at their "max" load said barely .357 Mag performance with 125-gr JHPs. The identical JHP as in their data. Even after correcting for my barrel vs. theirs, it was still more than 200 fps slower than what the charts say.

I don't think it behaves the way they think in cases with a lot of room.

Your 20-inch barrel might even be displaying the slowdown sometimes seen with long-barrel .22 LR guns--the powder gas gets down to a pressure where it's no longer propelling the bullet, letting friction reduce the muzzle velocity. I have never seen any formal quantification of this effect, but it sounds plausible. The rumor when I heard it was max speed with a .22 is reached in about 16 inches, it doesn't increase for another few inches of barrel, then slows down a bit.

That theory is subject to confirmation, of course.

Why don't you try them in a 6- or 8-inch revolver and see what you get? I would expect them to be slower than from your levergun, but the slowest one might become the fastest one...maybe.

[10mmShooter]

Interesting Grump, I really didn't considered that, my testing with Autocomp in large revolver cases was short lived, I was able to secure enough sr-4756, and No 5. to meet my needs. So I didn't need to test Autocomp in my revolvers any further. I still have several pounds of AutoComp, I'll likely just shoot it up in my 10mm's.

Supposedly from Winchester literature the purpose of Autocomp was to generate more gas, I suppose the theory was the extra gas would benefit compensated guns in competition. No really sure that any of us could test this theory, since the only thing we can measure is velocity.