There are several schools of though on alloy. Lyman #2 is a fine alloy. I have just never found the need to spend the extra money. I have always gotten good performance, and good fill out with straight WW. I just make sure I flux it very well.

You need to check your brass. This cartridge does have some different length brass. Do a search on the 38-55. I am sure there are other people who can explain it better than I can. I just know that the different length brass exists, and must be accounted for.