I am loading .351 WSL for a 1907 Winchester and don't like the initial results. Any ideas? I made the cases from .223 Remington, cutting them off behind the shoulder, expanding, and trimming to length. I used a starting load of 16 grains IMR 4227. Bullets were cast from an NEI mould. I don't have the mould anymore, I will be switching to the Lyman bullet for this cartridge when I use up the NEI's I had already cast. It is a plain base bullet. I sized .350 in a sizer I had for .348 Win. Cases came out pretty dirty, which is about right for a starting load. All cycled the action. 3 or 4 appear to have pierced primers. All have pretty heavy firing pin strikes. I didn't notice any gas escaping. The 1907 Winchester is pretty much closed at the back end. Gun is a relatively late one, serial in the 53,000 range. Condition is excellent. First time I have fired this gun. I am concerned about the heavy firing pin strikes and pierced primers, I never saw that before. Primers were well seated.
Any suggestions?
Thanks,
Bruce