jethro75
Member
I loaded up some 100gr SP 243 for my TC Encore rifle and shot them the other day. I had loads (3 shots each) of IMR 4064 from 33.5 to 36 grains. The Sierra book says min 33 max 36.5 for 100grn bullets. I worked up and noticed when I got to 35grns the primers started to flatten pretty good. The brass is winchester once fired with federal primers. I cant figure why its doing this. I double checked everything I can think of. The only possible thing I could think of is I checked the OAL with a stoney point guage and it came out to be right on with the books. I think I may need to seat them a little deeper to get them aff the lands a little more. Does this make sense and could it work or should I just use a lighter load? Its not shooting too bad but it seemed the groups were starting to shrink then I noticed the primers were flattening. Any help or thoughts would be great.