When I first started getting serious about handloading in the early '90s, I read somewhere that 6.5 grains of Red Dot was a good load under any bullet in the .45 Colt. I shot a lot of that load from the 195 grain 452488 up to various 150-255 grain bullets, seems to hold true.
I'm real late to this party but I've shot the 6 grain load of Red Dot for about 30 years. It is as accurate as I'm able to be...and probably more so. Have used all the "traditional" lead bullets but have yet to try the RCBS 270SAA, though I have the mold. One of the most accurate loads I used was a 265 grain SWC from a commercial caster in Florida (now out of business.) It had a fairly long bearing surface and I'm sure that had something to contribute to its pleasing accuracy. In my experience, it's pretty dirty and soots up the cases a tad...but that about the only negative for me. It does require me to be consistent in my use of the powder measure, in order to throw accurate, consistent charges.
Just looked and my Red Dot loads ran from 4.5 to 5.5. They were .45 [45colt-acp-AR and Schofield] CAS loads shot duelist style out of Ruger Vaqueros, DA Webleys, Colts and Smiths.
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |