I did some back to back testing in my win mag with these to see what the difference was and wanted to get the loads identical with different primers to see if I could get more or less out of my rifle. What I found, is running RL17 powder in my case, I needed to use .8 grains more powder with the standard LR primer to achieve the same velocity as the Magnum primer. both were FGMM primers, identical cases, powder, bullets, shooting day, chrono etc. SD never went over 6.0 regardless of which I used for 5 round groups, accuracy never changed, so I went with the Magnum to save powder/case space, and because I had a ton of them already. Your results may vary, and I have not done the same test in my current rifle, but that's what I got out of the Remington. I shoot in AZ, and it was prob 85 or so degrees out during this testing during "winter".