Over years of shooting heavies (88s, 90s, 95s) from .223 Rem F-TR rifles, at one time or another I have tried Varget, H4895, N140, Benchmark, 8208 XBR, IMR 4166, and H322. In my hands, none of them come close to H4895 in terms of pure precision, or in terms of velocity in a tuned load. Of course, the trade-off for that can be brass life if you're pushing them hard.
For the OP, N140 generated velocities fairly close to those of Varget on a per charge weight basis, but I found the transition to over-pressure conditions to be very abrupt with N140. However, N140 seems to work quite well in .308 heavy bullet applications. More recently, I have noticed .223 Rem heavy bullet shooters using N135 with what appear to be excellent results, but I have not tried it myself. There are also a few F-TR shooters that have used N150 in this application. In general, any of the powders I have listed here could probably be made to work acceptably. In other words, the list of powders that will work for this application is pretty generous. The primary difference will be in the final velocity of tuned loads, although some of the powders also seem to provide slightly better precision than others. So with the current difficulties of obtaining reloading components, I'd start with whatever powders you actually have that fall into the burn rate range from slightly slower than Varget up to about H322.
Edited to add: any of these powders can cause a carbon ring; I have not found one to be noticeably worse in terms of carbon fouling than another. Proper cleaning technique using a bronze brush should take care of that, anyhow.
