You might consider a very small grained powder that is faster than you might normally choose for that bullet weight. The advantages are that you might still be able to obtain reasonable velocity and precision without going way over MAX pressure, or heavily compressing loads due to the lack of boiler room, a [relatively short] 26" barrel, and a heavy bullet with a very long bearing surface.
For those very reasons, I used H322 in a load for a 26"-barreled .223 Rem bolt rifle that had a very short freebore with Berger's 80.5 Fullbore bullet. It didn't take nearly as much of such a fine grained and fast powder to get the 80.5s moving as it would with a slower and more bulky powder like Varget. I started at 21.5 gr and worked up VERY carefully, ending up at 22.5 gr of H322 final, which gave me something in the neighborhood of ~2850 fps. That A-Max has a pretty long bearing surface; it has approximately .a 017" longer BTO dimension than the 80.5 Berger, so if you decide to go this route with a fast, fined grained powder, be sure to start plenty low and work up safely. If you have access to a reloading program like QuickLoad, it can be very useful in circumstances such as this.