Depends on which gun you want to put it in.
Lik if a NEF, buy a NEF 12ga Ultra slug gun,
have your smith ream chamber to 3.5",
order brass 3.5" cases from RMC, 10 for $100.
You can also shoot 3.5" plastic and get real
strong loads. plastic Cases for reloading are 17 bucks
primed for a hundred. Get a BPI catalog so you can
see what is available. Like roll crimper, different slugs,
seals wads, sabots. To double up pad I just get a
thick slip on Limbsaver at gunshop and put it over the original
pad. I add more weight to the butt using extra holes
in butt filled with weight.Ultra has one weight in
the butt from the factory. I add more.
Getting to some more 4ga/bore work.With barrel and
falling block action locked down fired off some blank
type loads to test the breach and firing pin I set up.
I fired it by hitting the back of firing pin with hammer,
as I now have get hammer and trigger setup. Firing pin
dents primers ok, breach works and headspace is ok.
For loads I have wads to take up space above powder.
Others with same 4ga case in doubles fill case about
1/6 full of Blue Dot (110gr), with 2000gr slug.
I'll use 1600 gr hollowbase slugs, with about 1/3 of a case
of IMR 4759 or 1/2 to 5/8 case of RE17, rest filled
with fiber wads.These are shotgun primer loads and I will
be using THE PRIMERS OUT OF KILN CASES at about same
price as BMG primers. And I have BMG primer cases also
that I will test also, once gun is finished in a few weeks.Ed