Join Date: Aug 2008
Location: Tahlequah, Cherokee Nation
Re: 6.5 Creedmoor ..Why?
The 6.5 Creedmore is designed to have more of the bearing surface of the bullet exposed from the case neck than the .260 Remington does and still be within the SAAMI Spec O.A.L. dimension of the .308 Winchester.
So, you don't have to seat heavy-for-caliber bullets so they intrude in to the combustion area of the case with the 6.5 Creedmore as with the .260 Remington.
The 6.5 Creedmore chamber specs have more of a leade in to the rifling, too. That plus exposed bearing surface limits bullet yaw prior to engagement with the rifling. That might not make a difference on your hunting rifle. It might matter on your target rifle. Or, it might not. But that's the idea.
Also, I think the 6.5 Creedmore has a higher operating pressure limit than the .260 Remington does.
One way to look at it is that the Creedmore makes more effective use of available common short action magazine length than the .260 does, where heavy-for-caliber bullet use is concerned. You could do the chamber of a .260 Remington with the kind of leade common with the 6.5 Creedmore, and then seat the bullets out to have more of the bearing surface of the bullet extending beyond the case neck, but the result will be too long to feed through magazines based on the .308 Winchester O.A.L. dimension.
BTW, "flight time" of the bullet isn't just a function of starting velocity, but also one of drag in flight, or deceleration. Highpower target shooters tend to use fairly heavy for caliber bullets for this reason -they tend to have higher ballistic coefficents and thus retain a higher percentage of starting velocity over distance.
Everything you ever wanted to know about the 6.5 Creedmore is probably easily found on Hornady's website, since it is their brainchild, based off their .30 T/C case, IIRC..