AA2520 was very popular with the M1a service rifle group when it first came out in the 80’s. I have shot kegs of the stuff. It shoots well in 308 and 30-06 service rifles, the port pressures are appropriate for M1a’s and M1’s. Accurate Arms told me that they blended AA2520 to give the same pressure curve as AA2495/IMR 4895 for the same charge weight.
I have used the stuff in .223, I got excellent groups with 69 SMK’s in the .223.
Some people confuse metering accuracy with on target accuracy, so those who believe that tend to like ball powders. AA2520 is a ball and throws extremely well. It does shoot well when you hit the sweet spot.
Still, I prefer stick powders over ball. Stick powders shoot well over a very wide charge spread and do not leave a lot of residue. AA2520 does leave a lot of residue which is not a real problem as I seldom shoot more than 88 rounds between cleanings.
I think if AA2520 dropped in popularity it might be due to that loads with Accurate Arms powders must be redeveloped with each new lot of Accurate Arms powder. Darn near each keg came from a different powder manufacturer. Loads that were OK with one lot of Accurate Arms powder will blow primers with the next. I have lots of AA2520 that are extremely dusty and will clog up my .223 Dillon powder funnel. The best lots came from China of all places.
I shot this group with AA2520 rapid fire with a M1a in a 100 yard reduced Highpower match
This was shot prone slow fire with 69 Noslers, AA2520 in .223. The most remarkable thing to me was that the mirage was so heavy I never saw my group until I was at the target butts. If I could have seen what I was doing the group might have been tighter.