SAAMI has different groove diameter specs for rifle and pistol for .44 magnum (see attached docs.), so cast bullets for rifles do have to be sized to a larger diameter than what you would probably size for a pistol. I've done well with cast bullets in microgroove rifling by following three simple rules: use a hard alloy (wheelweight metal is hard enough), size 1-2 thousandths over groove diameter, and use a gas check.
https://saami.org/wp-content/upload...CFR-Approved-2015-12-14-Posting-Copy.pdfhttps://saami.org/wp-content/upload...d-R-Approved-2015-12-14-Posting-Copy.pdf
