Re: considering a .260 project
I second the idea of building the 260 on a long action ,you'll have plenty of magazine to seat the long bullets way out for better case life and more case volume.
I built a 308 on a LA Rem 700 with the idea that I was gonna shoot the 210gr Bergers , ended up shooting the 190's but they would have never fit in a Short action mag.
And like it was mentioned if you shoot the barrel out or feel the need for more speed then you can rechamber to the 6.5-284 , 6.5-06 , or the 264 win mag and several others.
I'm currently having a 260 built ,but on a short action ,I decided against the improved version due to the added steps in making the brass hence eating up barrel life. I plan to use 308 Lapua brass necked down , the chamber is a tight so I'll probably have to turn the necks a little maybe only 60-70% from what the smith says , if that is at all.
Ballisticaly , look at the BC of a 140 gr A-max and look at the speed you can get 2600-2800 , if you campair it to a 300 Win mag shooting a 220gr SMK its realy close if not a little better but with a hell of alot less recoil , noise , bowder and longer barrel life (ask Shawn Carlock) I talked to him a bit about why he shoot this caliber in comps.
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