For those of you who use rifle brass for 410 loads what case do you prefer? 303brit 444 marlin or 9.3x74r or magtech 410brass?
This is an old thread but, it may still be relevant to the OP but if so, I load BP for my .410 these days as well as for 12ga years ago. My observations thus far are these. For 12ga, plastic hulls work great. I get them for free from trap shooters which is necessary if you want to shoot black out of plastic as the hull will have holes melted in them after one shot with black. I would cut the crimp off, load powder, over powder wad, lubed fibre wad, over shot card, shot, over shot card then roll crimped. The reason for cutting off the crimp is twofold. First, I get a better roll crimp with the star crimp gone and, more importantly, I was loading them for vintage shotguns with laminated barrels which most were 2 1/2” chambers. For my .410, I use brass made from .303 Brit but I also have a box of mag techs. Fire forming takes two pows to get a complete form. First is 20gr WW231, filled with cereal (cream of wheat or sunny boy) then plugged with a wad of Kleenex. This will blow out the end 2/3 of the case. second forming load is 25gr Was231 with 30 or 40 grains of shot, then filled with cereal. This will blow out the bottom 2/3 of the case. Any time I increased the charge to do the form in a single go, it would blow the end of the case off. Loading them for use, I load 35gr fff, card wad (cut from milk carton), then 1/8” felt wad, then 1/8” felt wad soaked in bear grease, then card, then 1/2oz shot, topped with another card, then sealed with bees wax dripped into the mouth of the case. I sometimes then press a number stamp into the wax denoting the shot size. Mag tech brass is MUCH better IMO and after buying the .303, then expending 2 primers and 40-45 grins of powder just to fireform and then have an inferior product, mag techs look pretty good. While I have never done it, I feel that should you want to fire form, the 9.3x74R is a better choice than the .303.