help deciding what to do with rifles

[N10sivern]

OK, let's start with a partial inventory of my rifles:

Bolt 6.5x55 with 28" barrel
Bolt 6.5x55 with 24" barrel
Bolt 300 WSM 24" barrel
Bolt 358 Win 20" barrel
AR10 7mm-08 24" barrel
AR10 358 Win 20" barrel
a few 243 hunting rifles
multiple 300AAC and 223 AR15's

Here is what I have to work with:

Savage SA receiver
AR15 receiver set
AR10 receiver set

My dilemma:
I have an AR15 receiver set that I want to do something special with. Possibly a 6.5 Grendel or 6mmAR. I really don't see a point in a long range 24" barrel 223. The Savage SA I was thinking about building a 308 with a 20-24" barrel. I do not own a 308 and have never been in love with the round, but maybe it's time. I considered a 6.5 Creedmoor but it isn't going to do anything I can't do with the 6.5x55. If I go 308 on the Savage receiver, I may build a 24" 260 or 6.5CM AR10 and sell off my 7mm-08 barrel and rebuild it as a 20" 308. I can't see having a 6.5 variant and a 7mm-08 AR10. There will be more variance between the 6.5 and 308 and 358. What do y'all think would be the best variations to go with.

 

[MudRunner2005]

Bolt Action - .308 Win
AR-15 - 6.5 Grendel
AR-10 - 6mm Creedmoor

 

[N10sivern]

Interesting. Didn't think about that

 

[MudRunner2005]

Interesting. Didn't think about that

I was just picking random cartridges you didn't already have, but also based on pretty stringent magazine length restrictions (AR platforms) the 6.5 Grendel for the AR-15 is about perfect, and given the mag restrictions in the AR-10, the heavy high-BC 6mm bullets would be able to get near the lands if you have reamer built to your specs. And based on your list, you're not adverse to the 6mm rifles (.243). Personally, I'm not a fan of any of the Creedmoor cartridges, but it would be unique and different in an AR, and Hornady is making 6mm Creedmoor brass now.

 

[Schnyd112]

I have seen a couple guys shooting 6mm fat rats. I think it is based of a 6.5 Grendel, but necked down, body lengthened and improved... I think. Similar to the 6mmAR but I have never seen the AR.

 

[N10sivern]

I've seen the 6mm fat rat mentioned but haven't seen a whole lot of info on reloading and barrels etc

 

[BEEMAN]

6.5X47 on your short action.