X2 on that!
As has already been mentioned, the list of powders that work well in 223's is very long and it's not a finicky cartridge to load for at all.
Longtrain said: "Just put on a new Hart 223 1:12 twist barrel. This is the first 1:12 I’ve had as I mostly shot heavy bullets in other 223 1:8’s. I plan to use 52-55 grain bullets.
I picked up a pound of LT-32, what about N133, AA2015 or RE7, etc? Looking for easy and accurate metering from a powder measure. Any powder rise above the others in terms of accuracy, performance and barrel life?"
Well, Hart makes one of the best button rifled barrels you can buy, I have a few of them, so you're certainly off to a great start.
With the powders you already have you'll likely be able to work up a load that serves you well. I haven't used any in awhile but one that I used to use a lot of in different 223's and it worked with a very wide range of bullet weights was Win 748. Win 748 has been around for a long time and as new powders have been developed it doesn't get used as much but that doesn't mean it still doesn't work extremely well in 223's and it's typically easy to find on the shelf and for less than the crazy 50 bucks a pound that a lot of powders are selling for now days. Also, Win 748 flows like water through a powder measure/dispenser. I use a lot of Hodgdon Benchmark with 53's in 223's and it too meters very consistently and shoots well but I don't know that it shoots any better then 748 and 748 always produced a little faster velocities.
My first 223 was a heavy barrel Olympic Arms AR I bought in 1986. It wasn't anything special but it shot the mid 50's really well with 748 and I loaded for it on a progressive. I have AR's now that are much fancier and cost way more but I don't know that any of them shoot any better then that HB Oly Arms AR did, go figure....