
A note about the BDG stock: it usually comes with a black unitised butt that screws to the main frame. This one I have modified to use a flat plate, that rides in a bag better and is a lot lighter than the original by about 500 grams. This was done to allow for the heavy barrel.
The chambering is for this round, developed by Laurie Ingram and Robert Chombart. Note the bullet is pointed, only just spotted that.

The idea behind the short neck and taller body (which are coincidental) in this 260 cartridge, is to simply gain more space in the case. Capacity is somewhat more than the 6,5x47L and closer to the 284. The body and shoulder angles etc are retained, but the chamber reamer is a custom to get the short neck, there is no leade, which is gained by a separate throating reamer.
Cases are formed from 308 Lapua units, necked down to .264 and fire formed to get the new shape. I have not shot this rifle yet, as I only chambered it this morning, but I know Laurie Ingram did a lot of work with it. Laurie was a bloke that did not follow tradition, which I can really relate to.
Bullets to be used are 123 and 139 grain Lapua Scenars (cost and availability are the main feature) and they work well. Powder at this point looks like ADI 2209 or 2213sc (as per the 6,5 x 55 or 6,5 x 284). Primers, as per another thread on this site, probably CCI BR2's. Hoping for around 2850-2900 fps performance with the 139 grainers, and more with the 123's.
The German 88mm round from WW2 shows the benefits of the short neck.