AR is accuratereloading.com and its big bore
forum. For 3.5" 870, using 600gr slugs with
77gr 4227. For 3" use 72gr 4227.
Maybe a little more if you can get
heavy alloy barrel with muzzles about one inch.

Here is 12ga prototype cushioned base sabot I put
together to show how heavy of powder seal
and heavy cushion base that is needed. That
eliminates the blowouts and damage that was
happening to sabots unless I put a card
under sabot. Just used a Brenekke seal/cushion
base, epoxied to bottom of sabot. Even fired one
and it got out the barrel and 437gr slug hit
target straight. Ed

[Linked Image]

Last edited by hubel458; 02/03/09.
Ed Hubel