Ruppster is correct, regulations state no all brass shells and no necked down shells for shotgun deer hunting. Regulations are silent on OAL, bullet proturding from the hull, and just about everything else. Diameter of the round can be no smaller than 410 bore or larger than 10 ga. The standard for a 410 bore is .410" plus 20 thousands (.430"), my barrel slugged @ 0.4295"
Tim I would love to use an all brass hull, I think the ones from Magtech have more case capacity than a 444 Marlin.
Bullet is a 310 grain WNFPGC from Oregon Trail I believe. It is the bullet that has silver in the alloy. I have also tried some 240 cast PB, 240 grain HP/XTP, 275 grain lead HPGCs and 330 grain lead plain base bullets. Horndays work fine as did the 275 grain GC HPs, the plain base bullets have not been very accurate, I think I am pushing them too hard.
I think the key to making this work is to have a very tight fit round. If the round is loose in the chamber the weak hull will expand too much and you will have a gas leak and loss of velocity. I hand fit each round to my gun and have eliminated leaks around the brass/plastic joint. The only pressure leaks I have had are at the rim and never bad enough to give a visibile notice while shooting. I can tell the difference in recoil when a shell leaks. Also, when you get to the limit of the hull you will get vertical stringing as each hull leaks a little differently.
The Winchester AA-HS hulls (2.5") are by far the strongest hulls I have tried. I have not had a case head leak with these hulls.
This gun when finished will still be a shotgun, not a CF rifle. The load is equivalent to a mid range power inline 50 MZ shooting a 300 grain sabot. The velocity will be well under the starting load for a 444 Marlin with the same bullet. My 12 ga. slug gun will shoot a heavier slug at a higher velocity than this 410 is capable of, however this gun doesn't punch me in the forehead everytime I pull the trigger.
BB