Some guys in 12ga like to use the Magtech brass cases
but the cases being brass the sides are thinner than
plastic, and that makes loose fit in 12ga chambers.
And case expand a lot and are harder to resize,
But I found that .750 hollowbase 10ga slug fits
those cases and still chambers ok. Not a sloppy fit.

So If you have a 12ga smooth barrel with full length
backbore job, of .850" bore or bigger you could use
the Magtech brass and ,850" size 10ga hollowbase slugs.

Brett in MN used the a BPI AQ slugs in his full length
backbored 12ga and got fair accuracy as he said the wads
under slugs expanded a lot for a decent fit.
The 10ga slug shown in the 2.5 inch Magtech is 800 gr,
and .850" diameter. These cases will take magnum
pressure so you can get good speed, for what this short
case can hold.

It is too bad they don't make 3" and 3.5" versions.
These 2.5" cases are easier to find and much less than
others, so if needing brass ones you can rig up guns
to work with them. To build a new barreled gun in actual
12ga size, IE .729" bore, you'd make chamber to
minimum specs so cases don't
over expand.ED

Here is the ytube URL again for our guy
shooting 585HE in his NEF----By mid summer we plan on a
pickup truck load of more 585HE cases coming in.

www.youtube.com/watch?v=HypaUdwQGAc