7.5 Swiss help!

[vellnueve]

I did the full length sizing of .284 Win brass to make it 7.5 Swiss. After crushing case #1, the next 21 came out fine. The problem came when I tested the seating depth in the rifle with a dummy and a dry erase marker. I read in one of my manuals that when properly seated the dry erase residue should not be touched. I set the COL at 3.050 and then tested it in the chamber. When I removed it, the bullet had clearly contacted something and was 2.933 in overall length. Moving it in to 2.893 resulted in no bullet-rifling contact (bullet is a 168 grain Sierra BTHP) but this seems much shorter than the recommended COL of 3.060 for this load and thus I'm worried about overpressure. Anyone give me some advice on how to proceed?

It looks like the bullet is fatter than the GP11 so perhaps that is the problem?

 

[1903Collector]

I remember reading somewhere on this board that K31s (if that is what you are loading for) have almost no throat, so you might be hitting the rifling. I have never loaded for this round so I can't give you much more than that.

 

[vellnueve]

I think I am too. I might have to go with a skinnier or shorter bullet... But would appreciate any more insights. I need a new load for it anyway as the load I was looking at using uses H4895, not the IMr 4895 I have on hand.

 

[1903Collector]

I think they are balistaclly equal

 

[vellnueve]

Apparently they are very close but not the same. I did find a load for it but that's assuming a 3.060 COL which my rifle will NOT chamber.

It chambers freely at 2.960 COL (tested via seating the bullet with the rifle as the seating die) but the dry erase marker line does not go away until 2.880.

Recipe calls for 42 grains starting and 44 grains max.