I have a 300RUM and 308Win I usually use for long range shooting, I'm looking to buy another rifle that is relatively cheap and in a new caliber I can reload for just for fun.  

I thought about a 6.5 PRC but doesn't look like brass is available.

I have a .300 suppressor I will use so its that caliber or smaller, I see a few rifles I can get under $500 chambered in 7mm Rem Mag and 6.5 cm. I considered a 300wsm but want a softer recoiling cartridge similar to my 308 or less. I can't imagine hunting past 350-400 yards with it on medium game. Leaning towards the 6.5CM, it seems to be superior to the 243 at the longer ranges from the reloading charts I am looking at.

My buddies like to shoot on the range out to 800 yards so not looking for something I have to mortar in at that range, I mainly use 4064 and Retumbo...any suggestions on what round to buy?

Get a 6.5C and burn up bulk-packed Hornady factory ammo for brass.

Right after I posted this I ended up selling one of my 10/22's and bought a ruger predator in 6.5 and pocketed the difference.

Ordered up some 143gr eld-x and will grab a spare nxs and see how it works.

277 Sig fury might be just the ticket.

6.5 cm or a 243 with a faster barrel for the heavier bullets...

These would be more economical than 7mm.

"but want a softer recoiling cartridge similar to my 308 or less" Don't get a 7mm then. I just built a 6.5 cm AR10 and I could shot that thing all damn day and then again the next day.  If you want really low recoil just build a grendel which is plenty capable at 300-400 yards

Or 6 Creedmoor

Ended up with a couple 6.5 PRC's and a .224 Grendel

7-08
It can produce some pretty good numbers better than many realize.
Not a barrel burner nor a powder hog.
Can shoot speedy 120s for whitetail 140s  and long range 160s. Brass is super easy to find and uses same powders as .308 very well in many cases.I am getting my 20b rechambered in 7-08.   Not many negatives with this guy