Got a bunch of 300g cast bullets. What powder/charge would you fellers suggest for a midrange load for my blackhawk ? Say 1,000ish fps.

4227 has always been my heavy bullet go to powder for .45 Colt.

What powder do you have on hand? As I recall, Briane Pierce had an article showing 1000 fps with 300's using unique. That said as much as I like Unique, I'd be using something a little slower like 2400.

I was out today shooting my custom 5 1/2" Old Model Blackhawk 45 Colt conversion prepping for an upcoming rifle elk hunt. My load used the RCBS 270 SAA SWC (from Montana Bullet Works) that weighs 285 grs as cast. I used 7.5 grs of Titegroup (per Pierce for SAAMI level loads) that should run right at 1000 fps and it proved to be the most accurate load I have fired from this particular piece. I would load 7 grs of Titegroup with your 300 gr slug and would expect 1000 fps.

Got unique as well as some slower stuff....296 and 2400 and some 'lil gun. Dont have any cast bullet data. Dont know how the slower powders do with less than full house loads. Seem to remember 296 being touchy in that regard.

You remember well, 296/110 need to be loaded very near maximum to be safe. You will only want to use Unique given what you have. Ten to eleven grains of Unique should meet the 1000 fps you seek, depending upon bullet used.

Accurate #7 12-14 grains should be in the neighborhood.

13-14 grs. Blue Dot, 11.5 gs. Longshot

I run 22 grains of 296 under a 300 grain XTP for 1093 fps from a 4 5\8" Vaquero. Might go a shade faster with a lead bullet of similar profile.

Blue Dot is what immediately jumped to mind with me.

IMR 4227