I took some additional pictures to illustrate my dilemma. I took an empty case and seated a bullet to the documented 1.550" OAL (I just seated it. I did not crimp it):
(Please forgive the rough texture of the bullets. These were the first I've ever cast. I think the mould wasn't hot enough. Lesson learned for next time...)
I then took a picture of this 1.550" cartridge next to one with the bullet seated to the "front groove" as suggested on the Lyman product website. Its OAL is 1.479":
I don't see how it's possible to both crimp this bullet on the "front groove" and obtain an OAL of 1.550". I can do one or the other but not both.
To add to my confusion, I found this picture in Ch 13., p. 58 of the Lyman Cast Bullet Handbook, 4th ed:
The author, Mike Venturino, is discussing the merits of seating the bullet to different depths. He says he likes to seat bullets for target rounds high so they engage the rifling when chambered. He likes to seat hunting rounds lower so the lubricated grooves are completely covered. He says nothing about the possible effects these various seating depths have on chamber pressures. He says nothing about adjusting powder charges to offset the changes in case volume. In fact, in Ch. 15, p.66, he writes:
"The moral of that story is that there is no set rule in regards to bullet seating depth and that experimentation pays dividends."As a newbie, I find this very confusing. Bullet seating depth clearly affects case volume which affects chamber pressures. Bullet seating depth also clearly affects OAL. If one is to load rounds only to the specified OAL, then there is no possible variation in bullet seating depth.
So what am I missing that will make all of this clear?
Last edited by RottenHam on Mon Jan 02, 2012 7:39 pm, edited 2 times in total.