I had a P-17 rechamberd,headspace questions, and choose a 308Norma over a 300WM. The box on a P-17 is 3.40 and a 300WM ends up about an 1/8" longer than the 308Norma. Until I found some Norma at a gunshow for a good price,I used 300WM and trimmed.

You can hunt longer with wind at your back