I assume the higher pressure of the .357 Mag leads to more complete combustion. Is this right? Even the dirtiest 357 seems to be leagues cleaner than any .38.

It's mother taught it to wash its hands after each shot! Yes higher pressures do tend to burn cleaner, however try 2400 in a maggie, yes its dirty!

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Are you comparing loads with lead bullets as opposed to loads with jacketed bullets? Lead loads tend to be much dirtier probably due to the lubricants used. I've never noticed any difference between 38 and 357 when shot with jacketed bullets.

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I've gotten to where I really prefer jacketed ammo because shooting the bare lead dirties up the gun. AND, I think firing .357's through the gun makes such an explosion it probably vaporizes any dirt (just kidding)...no seriously, it is like a nuclear explosion in there when I shoot it...fire coming out all over the place (still just kidding). But, all joking aside, it is a monster. B

I think the .357 explosion pressure is 35,000 PSI! More than twice that of the .38 rounds.

bassoneer you want some fun? try 125gr full power .357 out of a 2 1/2 barrel! ye gawds!

Yeah, I run those in my 2 1/4" Taurus 605. You can feel the shock wave from the muzzle blast go right through your head.

I've been shooting 158gr. magnums recently and they are relatively mild compared to the 125 grainers. But, I emphasize, "relatively" mild. They still produce enough of a flash and boom to wake up the other shooters. This morning I fired some 158gr. magnums from my 686 and within a minute or so there were 3 or 4 curious people standing behind me to see what was making all that racket.

Back to the subject, I do think that the magnum rounds tend to burn somewhat more cleanly than many .38s. I'm presently firing magnums by HSM, sold via Cabellas, and they're pretty clean. The cleanest round I ever fired was Remington UMC 125gr. leadless magnums. I swear, the gun seemed to be cleaner after I fired those rounds than before I began. However, these are REALLY hot rounds and more than a tad too painful to shoot for my delicate hands, except on special occasions.

Howdy

Pressure, pure and simple. The higher pressure 357 Mag loads expand to seal the case better, which leads to less blowby, and all Smokeless powders burn more efficiently at higher pressures.

PRESSURE....

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The general statement is not true.
You obviously never shot any lead .357s over 2400.

All else being equal, higher pressure tends to leave less visible residue, which is not always the same as cleaner or easier to clean....