So, What Velocities Do You REALLY Get with AutoCom?

[Grump]

My habit now is to do a reality check with QuickLOAD before starting my load workup. The program still doesn't have AutoComp, nor its reported burn rate/charge weight twin CFE Pistol (I think that's the one).

My .357 Magnum results are curious, and more in line with what I used to get with the old Alliant data. SLOW, even when accounting for barrel length, much more even than quadrupling the effects of barrel/cylinder gap.

So now I am looking for some more data points.

Anyone have any experiences to report??? I'm most interested in 125-gr JHPs, but anything is more real-world info than I have now.

I tweaked QuickLOAD's powder info for another one that closely matched my charge weight/velocity results, real-world with my fired case capacity and adjusting for barrel length.

Using that same 9mm-predicting powder file, I ran QuickLOAD and loaded a workup to the "official" max charge. Wow, Way slower than QL predicted, almost 250 fps. QL was predicting almost the same speed as "official".

Not surprised that a powder would behave very differently in a much larger case...

By the way, the primers on the highest load pretty much matched some .38 Special factory stuff I have...

 

[LE-28]

The only experience with Auto-Comp in .357 magnum wasn't very good. It burned really dirty and I didn't get what I expected from it.

It was designed for high efficiency loads like 9mm and 40 S&W with compensated barrels and really is out of it's realm in the .357mag. I tried it when powder was hard to get but the rest of my single pound of it is under my loading bench somewhere.

I haven't used it since.

 

[Grump]

CAUTION: The following post includes loading data beyond or not covered by currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The Firing Line, nor the staff of TFL assume any liability for any damage or injury resulting from use of this information.

AutoComp in the .357 Magnum seems to burn cleaner (at least with 125-gr JHPs) just below the top of the website's published maximum.

LE-28: Was your disappointment with the dirty burn with the loads you tried, the speeds attained, the accuracy, something else or any combination??? I would appreciate it if you could post your charges, barrel length, bullet(s) and velocities.

I have reached a speed with this revolver that I want, and had pretty good accuracy at 50 yards with the top two loads even with quite unfavorable conditions for its red dot sight facing the sun (have to avoid bogus results spawned by the powder gas cloud tripping the first or last sensor or whatever got me 3,XXX fps readings from a 1250-or-so fps load...).

All with Winchester nickel plated brass
CCI 500 primers
Hornady 125-gr XTP HPs, crimped to top of channelure

9.2 gr: 1,320 fps SD 15.6 ES 31.3

9.58 gr: 1,350 fps SD 38.7 ES 103 (???don't know what's up???)

9.95 gr: 1,370 fps SD 39.1 ES 105 Shot a nice group...

10.32 gr: 1,425 fps SD 17.8 ES 45

All cases ejected normally, no problems.

All primers looked good--radius still there, last two loads only a hint of wanting to bend into the oversized firing pin hole in the recoil bushing. It's less severe than the typical Glock firing pin mark.

Don't try this at home, kids, but this is what I got.

This is a blued revolver so maybe I can't really tell what's dirty...

 

[44 AMP]

Sorry, I can't help with either the powder data or the computer program, I don't use either one.

What I can tell you is that if you happen to get, from your gun and your ammo the same exact thing they list in the books or on the computer, it is pure serendipity.

Somewhere close is normal, and expected but every gun and ammo combination is different, and some guns are "faster", some "slower". Variations of even 100fps between guns shooting the same ammo, from the same barrel lengths are not unheard of.

Don't get hung up over a handful of fps difference between sources, or between sources and your personal reality.

 

[Grump]

I'm not obsessing over a handful of fps.

QuickLOAD using my tweaked data came within 23 fps for all 4 loads. It was within 1 fps of one.

I've seen two 6-inch wheel guns shoot about 75 fps different. The slow one was like 20 fps faster than a third one, a 4-inch.

A 250-fps discrepancy for a charge weight tells me something is amiss. Ejection and primers AND most importantly the velocity tells me I'm okay. The first two "signs" IMO can tell us if it is (way) over spec, but not really if it's IN spec except for the real powder-puff loads.