My supply of AA2520 is dwindling, and I'm looking for a replacement since no one seems to have any in stock. I currently use it in 6.5JDJ, 309JDJ, 358JDJ, 375JDJ, 223 Rem, and 308 Win. I'm looking for one powder to use in all of these that will meter well through a RCBS Uniflow powder measure, and of course is in stock somewhere. Thanks in advance for your suggestions.

Varget is what I use in the 6.5, 309, and 375. In the 308 and 223, there are a couple of loads I just love! I have a lot of Varget stashed away due to using it in everything pretty much and it's not temp sensitive like the 2520 has been with extreme temp changes in KS.

Varget can be used in all those. My 6.5JDJ works great with Varget. It's one of those powders I buy when I see it.

H4895 is my go to in the 375 JDJ, 308 and 223. 4064 will work fairly well to.

Brenden

Reloader 15 works very well for me in most of those, and will probably work in all of them.

Of the alternatives that you have been given, only 4064 is Temp Sensitive. so,, you should find good results. Varget has been quite accurate, but did give lower velocities than 4895.
8208 XBR might work for you. It has done good for me with the lighter bullets. It also is NON Temp Sensitive.