I just started testing some Lapua 284 brass in my 30-284ai and have found that the neck diameter is much larger near the shoulder junction after sizing. I initially used Peterson 284 and didn't see hardly any variation in sized and loaded neck diameter through the whole neck length, even with 10-11x fired brass. I'm wondering what the cause of this is.
I necked up then fireformed my Lapua with a medium load behind 175smk. Then used 14 pieces to find pressure with this lot of powder. Upon resizing some of those 14 pieces, I found that one case neck near the shoulder measures 0.345 where it should measure 0.3365! It chambers but with resistance. Sharpied the neck and it looks like it hits at the shoulder junction, not the neck ....
The sizing is a FL die, expander removed, shoulder bumped 0.002. then used a mandrel to expand the neck.
If I use the expander ball in the FL die, it's not as large a difference in neck diameter, but it's still there.
I never had this issue with Peterson. I don't want to have to neck turn (chamber neck is a parallel 0.3425) or have the chamber neck opened near the shoulder.
Thoughts?
I necked up then fireformed my Lapua with a medium load behind 175smk. Then used 14 pieces to find pressure with this lot of powder. Upon resizing some of those 14 pieces, I found that one case neck near the shoulder measures 0.345 where it should measure 0.3365! It chambers but with resistance. Sharpied the neck and it looks like it hits at the shoulder junction, not the neck ....
The sizing is a FL die, expander removed, shoulder bumped 0.002. then used a mandrel to expand the neck.
If I use the expander ball in the FL die, it's not as large a difference in neck diameter, but it's still there.
I never had this issue with Peterson. I don't want to have to neck turn (chamber neck is a parallel 0.3425) or have the chamber neck opened near the shoulder.
Thoughts?