Are 158 GR. HDY XTP the same as 158 GR. CAST LSWC?

[Total Safety]

Hello
I'm looking to load some handgun .357 magnum using 158 gr commercial hard cast LSWC with a diameter of .357 using Hodgdon Universal powder. I reviewed the Hodgdon site and the COL for cast is 1.161 while the COL for the HDY XTP is 1.580. I am new to cast bullets and read that cast diameter is usually 0.001 larger than jacketed bullets (HDY XTP is .357). The cast lead bullet's crimp groove gives me a COL of 1.580.

They will be light loads and just wanted to make sure I'm not pushing the pressure.

Thanks for your advice.

[FullTang]

Your question is a little different from the title of your post, but if you're asking if it's OK to seat the cast boolit at the crimp grove for a shorter COL than specified in the load data, then the answer is yes, as long as you're well below max pressure. Most cast boolit load data is way below max pressure, but be sure to check. Seating deeper will increase pressure, and usually velocity, too. However, it is the usual practice to seat cast boolits at the crimp groove, and jacketed bullets at the cannelure, it's just that there are all kinds of different shapes and patterns out there, so Hodgdon simply specifies what they did in their test loads.

Your LSWCs should be .358 in diameter, unless you ordered them sized at .357; some match barrels shoot better with .357, but I'm guessing that's not what you have. Hope that doesn't cause you leading from blow-by.

[Total Safety]

Thank you FullTang for the OAL info. I doubled checked and the LSWCs are .358 in diameter. I must have looked at the label indicating the caliber they should be used in and didn't see the fine print indicating .358 diameter.

[tazman]

Since you specified that you will be using lighter charges, you should not need to worry. Cast boolits are forgiving of pressure unless you are pushing them hard.

[waco]

Some commercial cast boolits are TOO hard IMO for light loads. You might run into leading issues from not pushing them hard enough.

You need enough pressure to "bump up" the boolit to make a good gas seal.

Your best answer is load some up and test them. The gun will tell you what it wants.

Waco

[Total Safety]

Great idea Waco, but the closest outdoor range is about an hour away from me. Indoor ranges around me won't allow cast due to lead issues. I'll just make up a few each with different powder charges and see what the gun likes.
Thanks all