Strange findings.

[Brick]

Right. I have a copy of Speer #10 which shows heavier charge weights than my Speer #13. I'll stick with current data. Too bad no one makes an electric strain gauge that could be attached to a rifle chamber or revolver cylinder and get a read out on actual PSI. That would really be interesting if we knew the yield strength of the steels. We build bridges out of steel with 60,000 PSI tensile strength, why not firearms too?

[Delkal]

I would load using the older Speer 10 for real max loads (but that is just me). A quick search said this was published in 1979 probably before SAAMI gelded the 357 mag.

If you get a chance chrony the newer published max loads. I will bet they are much lower than published and not even approaching commercial ammo.

[abner13]

Primers and powder burn rate and pressure can vary from lot to lot , year to year.

NEVER start with MAX loads!

[Brick]

Well here's the results of some of my testing to date. Oct 8 of last year I wanted to see what my then brand new little Winchester M1892 would do (20" bbl). 125 gr. Remington SP averaged 2110 fps with a std. Deviation of 41.2 Winchester 158 gr. SP avg. 1732 fps with Sd 24.8

Next step was testing in my S&W Mod 627 (4" bbl). My idea was a good revolver load would be a good carbine load too. Close but not quite. for the Hornady 140gr JHP/XTP results were WILD! sometimes lower charge weights showed higher velocities Starting charge for H110 yielded 1290 fps with Sd at 58.2, but near max load gave only 1233 fps with Sd 42.1. So for that powder/bullet combo I chose a midrange charge that avgs. 1193 fps but has the lowest Sd of 31.3

Using W296 with the same bullet gave me equally confusing results. Starting load (same charge weight as H110) avg. 1170 but really crappy Sd 85.8 , near mx charge 1216 fps Sd of 28.5. So the best load was midrange giving me 1219 fps and Sd 28.8

Testing of these two powders with the Sierra 140 gr JHP was next again some lower charge weights gave higher velocities but I settled on less than maximum loads for W296 I get 1244 fps and Sd 24.97. H110 below max. was 1168 fps with Sd 20.92 Max ran 1228 fps with Sd 36.33

Just for grins and giggles I tested some loads with A#5 and the Sieera 140 gr. bullet Start load gave me an avg 1084 fps with Sd 25.80 fastest load was 0.2 grs BELOW max at 1181 fps and Sd 42.08.

Overall consistency is NOT great given the crummy Standard Deviations.

Next step was testing my chosen loads in my Carbine So the Hornady bullet (140 gr JHP/XTP) H110 ran 1916 fps with Sd 24.24, W296 ran 1960 fps with Sd 22.82. For the Sierra (140 gr. JHP) H110 1951 fps Sd 17.83, W296 2033 FPS Sd 18.35, A#5 1646 fps Sd 31.08.

Then Came Blue Dot! Starting with the S&W 627 at starting charge weight 1355 fps and Sd 27.47 (so I sez to myself WOW I sez) 0.7 grs later I'm getting an avg of 1458 fps with Sd 21.28 shortly after that velocity fell by 10 fps and SD grew to 84.92 and the cases are sticking in the cylinder and I should have STOPPED there 1 gr. over Sierra's published Max for rifle (as tested using a Marlin 1894) anyhow 0.6 grs later after switching to the Carbine I get 1954 fps and Sd 22.18 the next step Max I get one shot off with a registered velocity of 2039 fps, a blown primer, cracked case and jammed action.

Days later I'm leafing through Sierra Ed 5 and I find a separate data section with loads for .357 Magnum Rifle! SHIT!