Re: Short or Long Action build
As mentioned above, the bolt face on your LA won't work on the 6.5x284. But, it is my opinion that if you intend to build a 6.5x284, then you should go with a LA.
I just made the mistake of building a 6.5x284 on a Sako M591 short action. This mag allows for COAL at 2.80. The 6.5x284 is a 3.10 COAL caliber. The 130 AB bullets have to seat very deep into the case, so I'm going to be changing this asap. I will convert my Sako to a 308 Win using an Obermeyer 11 twist D-3 SS 5R bbl that I should receive by Tuesday next week at the latest.
I have a Stiller Predator action that will be mailed to my FFL by November. I'm taking the LW bbl off the Sako and having the current threads cut off and have the bbl rethreaded for the Stiller action. There is plenty of length at the breech to do this.
Moral: don't build a 6.5x284 on a short action unless the mag can hold a loaded round at 3.10 or a little longer. Make sure your bolt faces match the intended calibers.
I own a 7mag and highly recommend the caliber.