Well, it’s probably best to start by asking what do you have in stock? Because trying to go out and get a specific powder just to try it out, can teach you what a dog feels like while chasing his tail.
The good news is that there’s a lot of options out there for .223 and a lot of them work very well.
There’s nothing wrong with Old School 748. Some say it’s a little dirty, but that’s relative.
Sticking with the old school theme, my Contender pistol loves 4895 and I’ve had good groups with 3031 as well.
Varget has given me excellent results, but at 27 grains you’re doing a compressed load which are a little fussy to handle and you can only seat the bullets so deep.
Benchmark and 8208 XBR have been great. If you can get them.
I have not shot BL-C or CFE 223, but they get a lot of air time and a lot of guys like them. I don’t use them because my go-to powders are doing double duty for .223 and other rifles, so I’m not looking to add horses to the crowded stable.
Obviously, extreme caution must be used when loading for someone else. I won’t go anywhere near max loads for anyone else but me. ALWAYS be sure to warn them about what to do should they experience a squib! A lot of people have never thought about this.
Grouse