38spl and 357mag using the same components-ish ?

My perspective is this. From all the discussions about powders I've read over the past couple years it would seem to me the answer is to move to a faster powder for light loads as opposed to a slow powder which in all discussions appears to burn best at higher loadings while the really fast powders do well at reduced to mid-range levels.

I would be looking at something at least as fast as W231/HP-38 or faster like Titegroup which seems to have developed quite a following. Also AA#2, Ramshot Competition also come to mind.

F <-----> S Powder burn rates I'd be moving <.
 
One reason the .38sp/.357 caliber is so popular is because of it's versatility and the broad spectrum of velocities, powders and projectiles that can be used in them. Magnum primers tho, as has been noted, are used based on powder, not on the word "magnum" in the caliber name. I tend to suggest to folks when they start reloading for handguns is to start with .357 because it is IMHO, the easiest of all the handgun calibers to reload for, and because there is so many components readily available and so much published info for it. It resizes easily and brass lasts a long time even if you abuse it.
 
Magnum primers are also used when they produce better velocity SD, but you have to test it to see if that happens with your component combination. You want to knock the charge down 5% when changing to a magnum primer, then work back to matching velocity to measure SD difference. I've seen them lower SD and improve accuracy in .30-06 firing easily ignited IMR single-base stick powders that weren't filling the case well (Garand loads). I've also seen them increase velocity SD, especially in smaller cases or when an easily ignited powder did fill the case well. You just have to try it and see.
 
Well I finally got out and shot some hand loads out of the new GP-100 6". The loads were as follows-ish ( the exact data in not in front of me )

158gr LRNFP ( X-treme bullets )
HP-38 - 3.6gr through 4.4gr
SPM primers
357 Fed brass
trim to 1.277
medium crimp

These loads were pretty mild and 4.0gr shot one ragged hole at 15yds . This seems like it could be a nice light plinking load . I'll go back and test a bunch more at the 4.0gr lever and see if it's still consistent .
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180gr XTP ( Hornady )
A-2400 10.4gr through 12.3gr
SPM primers
357 Fed brass
trim to 1.277
Heavy crimp

These were intended to be full power magnum loads . They started out not to heavy on recoil but still much more then the above load ever got . As the charges increased so did the recoil . by the time I got to 11.8gr and higher the gun was really thumping the hand . By far the most accurate load was 11.0gr but 12gr was not to bad either . These were some heavy loads but all cases extracted freely . I even took the 12.2gr cases out after shooting by just tipping the gun/cylinder up and the cases just fell out with out even needing the use of the ejection rod .

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125gr XTP ( Hornady )
CFE pistol - 7.0r through 8.0gr
SPM primers
Trim to 1.277
medium crimp

This load was interesting . As CFE pistol has done for me in both 9mm and 45acp . It left the same very scorched and sooty case mouths . How ever every load shot really well as in any one of the 8 loads will shoot expectable groups .


All in all I'm pretty happy with my results :)
 
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I made a rookie mistake in case prep . Not sure why I did not consider the case growing in length after I sized them . I cleaned and trimmed all cases before loading on my Lee CTP . Trimmed to 1.277 which was the smallest case length so I trimmed to that . I now see once they are sized they grow to 1.285 +/- a tad . I have to say I'm a little surprised a straight walled case is growing that much .008 .
 
Given a gun capable of handling 35,000psi pressure, the main difference between .38 special and .357 magnum is the amount of space under the bullet. This is conventionally referred to by the cartridge overall length (OAL) specification. The OAL specification for a cartridge with a given bullet will determine the amount of space in there.

Because the .38 Special case is shorter, it has a lower maximum OAL for a given bullet length. The .357 case is .125" longer, so with a given bullet the OAL can be that much greater before the bullet is no longer in the case.

.357, on the other hand, may have a higher practical minimum OAL. If you seat the bullet too deeply, you may not have anything to crimp to. Wadcutters can be deeply seated and the crimp formed over the leading edge, but bullets with ogives and crimp grooves might require an OAL where the bullet's base is far above where it would be for .38 Special.

Because the "powder density" or "% case filling" (as reflected in the OAL specification) is different from .38 Special to .357, the resulting pressure curves and consequently the data from one load doesn't apply to the other.

Using a greater OAL reduces peak pressure in a revolver cartridge given all the other variables remain the same. But reducing the powder density can have the effect of inconsistent velocities. You can also encounter problems where a small amount of powder, especially slow powder, fails to ignite before the pressure from a primer, especially a magnum primer unseats the bullet, possibly even as far as the b/c gap.

Beyond that, it's not clear what your goals are. If you understand that besides bullet mass, bullet type, powder type, powder mass, and primer, the OAL has a big effect on the result, then you might start by setting a goal and fixing some of the variables.
 
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