Been frettin' over my next build. Decided I want a "do all" gun. Which includes 600yd matches and killin' shit. It will be a 6.5mm. 260AI, 6.5 Creedmoor, or 6.5x47 Lapua.

The latter 2 allow a longer case neck and less bullet protrusion. The Lapua has a smaller primer than the Creedmoor or 260. Somebody tell me what and why........

Should add, this rifle will sport a 21" #5 contour barrel.....

What about the 6.5 Grendel or 6.5x284? A CZ 527 or a small Sako in 6.5 Grendel would be fun.

I'd not be too keen on all the brass bullshit, so 260/260AI would be my choice. Go Wyatts if you are worried about room? What stock have you got in mind?

I have (2) 260's and both shoot lights out.
One is an ultra lite Remington model 7 with a 22 inch barrel that shoots light out. 100Gr bullets are scooting out at 3250 FPS.
The other is on a 700 action with a truck axle for a barrel. have shot several sub .2 inch groups with it as well. I am running 123gr SMK's in that one.
Brass is cheap (compared to 6.5x47) easy to get or make. Load and go, no muss, no fuss. In a pinch, you can buy it off the shelf.
Dies are easy to come by.
What is not to like.

lite weight

6.5x284 is too much of a barrel burner compared to the others. If I was wanting to shoot 1000yd competition instead of 600yd, I'd go 6.5x284. Otherwise, the extra powder, HP, and throat erosion is not needed. I also prefer a 6.5x284 to be on a long action. Grendel was made for AR-15. It doesn't make sense to me compared to the others, in a bolt gun.......

I have checked the 6.5x284 vs the 260 and can not see that the 6.5x284 is any better. FPS looks to go to the 260 if all else is equal.
The only plus I could see is that you can get 6.5x284 Lapua brass straight out of the box. You would have to neck down or up to make 260 brass with a Lapua head stamp. Lapua headstamp does not mean anything to me. If you are trying to get the last.001 out of your gun, your going to work the brass over anyway, so why pay 3x the price on the front end to come out with detailed brass on the back end.

The 6.5x284 will definitely out run the the 260 IMO, especially if it is in a long action. With a price, of course.

I have been leaning toward the 6.5x47. Buying a couple hundred Lapua brass and runnin' the dogshit out of it is a process I'm very familiar with. Although the 260 is probably a more feasible choice, logic has never gotten in the way of my gun purchases.......

I've got a 6.5BDC. Basically the 6.5x284 with the shoulder pushed back and a long neck. Works great in a short action with AI mags or a Wyatt's box.

The 6.5x284 will tear ass on a straight or AI 260 with any bullet I have ever tried.

I personally like the 260 AI for what you mention above. EASY 600 yard gun.