[Unclenick]

Welcome to the forum.

Well, they will fit and they will fire, except maybe if you've got a revolver with soft mainspring. The main thing is that the rifle magnum primer makes a larger volume of gas than either standard rifle or either pistol primer. If it unseats your bullet before the powder gets burning (and it may) there is a chance you will get a squib load, with the powder venting out of the barrel/cylinder gap or backward around an unexpanded case in the chamber, leaving a bullet stuck in the barrel for your trouble. If the gun is a single shot, it may work OK. Typically, these high gas volume primers give higher muzzle velocity extreme spread when used in a case that's too small for their intended purpose.

On the other hand, it may fire OK, in which case you want to be sure your powder charge is reduced 10% to start. The higher pressure in the case, if the bullet doesn't unseat too early, will start the powder burning faster than usual, raising peak pressure some. So you want to start light and work up while watching for pressure signs. I would probably avoid using it with a powder you can't reduce the loads on safely, like H110/296. I would fire only one at a time during workup in a revolver and check to be sure I saw a bullet hole in the target and that nothing was stuck in the barrel before firing again.