Lots of SRM were in 7x57,,it's a nice sporting cartridge too.
Any of the x57's really. Depends on what you want to use it for.
.300savage ain't bad.
As far as the oct front ring,,I'd instead use the extra material in the Turk to shape a 'square bridge' front ring.
The rear ring can be built up into a matching square bridge in any of several different ways.
I stumbled on this one the other night. I am not the seller, nor do I have any interest in it!
http://www.gunbroker.com/Auction/ViewItem.aspx?Item=336603004
