.38 JSP Load data same as JHP?

[hdcd]

Total newbie here. Getting ready to load my first .38 spl rounds. I've got some 158gr JSP from Zero and am wondering I use the same load data as for JHP?

I'm checking as the max load for cast is less than the beginning load for JHP.

Thanks!

[bumpo628]

You can use the JHP load data for any jacketed bullet.

The cast lead data is lower since the bullet diameter is larger and therefore will increase the pressure in the case. There needs to be less powder to prevent failure.

[hdcd]

Excellent! Thank you.

[jwb28]

I think it has more to do with lead bullets are generally kept to 1000fps or less to avoid leading the barrel than the dia of the bullet being bigger. That and lead has less friction in the barrel than a brass/copper jacket, so less powder is needed to get xxx velocity. Hard cast can be driven faster than a jacketed bullet, but you get penetration not expansion.
Anyway it's always best to use the data published for the particular bullet your using. People make substitutions, but they should start low and work up. another factor is the actual amount of surface in contact with the rifling. Less bullet making contact, less friction, less pressure.

[sequoia_nomad]

As long as the bullet weight and construction are the same, you should be fine. Jacketed and cast lead loads are not interchangeable, regardless of bullet weight. Just remember that different bullet profiles will alter the oal, although since it's a .38 if you seat to the cannelure you should be safe.

[spencerhut]

You can use the JHP load data for any jacketed bullet.

The cast lead data is lower since the bullet diameter is larger and therefore will increase the pressure in the case. There needs to be less powder to prevent failure.

Sure use the JHP data -10% to start and work up carefully.

The lead data is lower for reasons other than what you suggest. Your understanding of lead bullets is incorrect.

[ojisan]

A lead bullet obturates (expands) when firing and fully engages and seals the rifling.
This does drive friction (resistance) up...and accordingly, pressures go up.
So, lead loads are usually loaded lighter and run slower than jacketed loads of the same bullet weight, particularly once we start running over 1,000 FPS.
When driven too fast (means lots of burning powder) , bare lead bullets suffer from flame cutting of the bullet base, which softens the lead so much that heavy leading of the barrel begins as the melted lead sticks to the barrel.
Crimping on a gas check (a hard metal "pie-pan") to the base of the bullet will allow higher velocities without leading due to flame cutting.
(Gas Checks seem to be rarely seen these days...but Buffalo Bore does use them on their "heavy" 38 Special +P loads...158 LSWC with a hollow point).
However, drive the lead bullet too fast, gas checked or not, and the bore friction will melt away lots of the bullet before it leaves the muzzle.

Jacketed bullets avoid all the problems of lead bullets.
They are normally carefully sized to match the bore diameter ( or + .001-002") and grip the rifling just enough to get a good spin.
So, these can be driven at much higher velocities without pressures going to high or the bullet self-destructing on its way down the bore.