Fatdaddy, the 45-70 compared to the 500 Mag as far as recoil/muzzle blast is. The 500 Mag has more muzzle blast. But with Marlin loads in the 45-70 the muzzle blast is not as bad but the felt recoil is right there with the 500 Mag.
atlanticfire, I have not had a problem with light primer strikes in either of my BFR. I also use the Lee hand primer and I make sure the primer is seated all the way in. If you don't seat the prime all the way in, you can get light primer strikes. The primer will push in and not ignite, leaving you with the light primer strikes, that is why they go off the second time, because the primer is nor properly seated.
I use WLR primers also in my 500 Mags.
But if you are still experiencing the problem, contact MR and have them look at the gun.