Re: Primers for 300 RUM w Retumbo
Obviously magnum cartridges do great with magnum primers, however, there is the issue of consistency.
You may find that using a regular primer like Fed. 210 match, the powder burns very evenly and uniformly.
I tried this when I noticed some pressure signs using Retumbo. I was getting 1/2" 3 shot groups but #4 and #5 shots were expanding to 1".
When I switched to the regular large rifle primer, the pressure went way down, I added powder, and got even better groups. But I do have a 28" barrel.
Good luck, and good shooting!