you need to know your neck size before you start loading. I have a greg tannel built 6.5-06 and it has a .293 neck, I can size 25-06 up no probs, but if I go 30-06 or 270 I have to neck turn. if your neck is in the .295 or better area you have more options. A-square makes brass, but standard brass in the cals I listed work great. If you have a fairly quick twist barrel you can fling the big bergers and SMK's. I have a bunch of rifles but the 6.5 is quickly becoming my favorite. the accuracy of the bullets in the better than .6 bc bullets is crazy, and I bang flopped two elk and a deer this year, all at ranges I won't say other than quite long. it could be the most under rated rig made.
if you load the big bullets RL25 is perfect, lots of guy run RL22 also. I came within 12fps with both but my ES was single digits with the 25. it is not a fast round and really should have a scope with turrets to do its best, but setup right you can hit stuff your buddies can't even see.
I took a deer yesterday on a cull hunt and my pard asked what I was shooting at, I told him I just canned a deer. I had him look through my spotter as he could not even see it with his bino's, in the snow.......it is a damn impressive performer.