I have been reloading for the better part of 14 years. Most of it was pistol for the first 8 or so, but I feel pretty comfortable behind a press. Anyway, I have been shooting and loading a bit of 458 Lott. The one problem I have been having is misfires. At least one out of every twenty rounds does not ignite. Dimple in the primer cup, but no lift off. The first go-around I blamed it entirely on not using enough force to seat the primers.

I prime off the top of a forster co-ax, which usually pushes them on down. This is the only caliber that has given me this problem. Never a misfire with a factory load. I have experienced misfires with WIN 748 and DP 74 (which gives sweet heart groups at 100 yards). The brass is Hornady.

About 30% of the cartridges will fire on the second try, but none will fire on the third. Flash holes are clean and I don't drink, so the obvious problems are not there. Powder in the cases. Use Federal or Federal magnum primers. It is just puzzling that this is happening. I would like to know if anyone else has had this problem. My rifle is an Ruger RSM.

Thank you for your input.
Spencer

If your factory ammo is firing fine, then probably nothing wrong w/ the firing pin. It could be a bad lot of primers. Are you full length sizing or partial sizing? Maybe you are just not quite getting the round completely seated in the chamber or the chamber is abit long & the round is seated to the belt & the headspace is abit long. A few things to consider.

Well I don't know, I don't think the problem is any of that, unless the Hornady brass has a long headspace, while the factory stuff doesn't.
Don't all Lotts headspace off the belt anyway?

Would I mind a quid for everyone having trouble with Fed primers?

If it is loose headspace, how does one adjust that on a straight case?

I'd try different primers, try Fed primers in used factory cases, and or check the headspace on/with Hornady brass.

Loose primer pockets?