The laws that clarify over 50 cal exemptions is Title 18-GCA 86. Shotgun
calibers exempt, existing in 86 exempt like 577NE, 600NE, etc, and those that
we ask ATF for an exemption for sporting use, which I did for my
585HE and 700HE, which many others like SSK, AHR etc have done
for their cases. And they go by .500" bore size so that all 50cals, with groove
diameter of .512" or less are not DDs.
Some have asked if the guy who made above
bolt action 8ga does them for others, no he only
did one for himself, and isn't a manufacturer.
Here is picture of a cast .504" slug BPI 12ga sabot
a guy made a few for me and it has good accuracy with
our slower powder loads, with the sabot working ok.
Slug is 440 gr and hard alloy cast with decent
meplat for good penetration.But it isn't too blunt
so it has good longer range capabilities when you
get the speed behind it. Soon be the deer season and
guys are still hunting for their ideal 12ga sabot/slug
setup for loading their own.BPI is supposed to have
a new sabot this year..Ed