Drover,
There is a 95 gr bullet from Hornady that seems light recoiling with a fairly quick burning powder like VV #133 or #135. It is a bit wind sensitive though. I have heard that Lapua has a new 100 gr bullet, but have not seen them as yet.
If the recoil of the 140 gr class of bullets is too much for you there is a 123 gr Lapua (or 120 gr SMK), 130 gr (VLD which will probably jump too far in a hunter rifle) or a 128 gr (10 cal ogive designed to come out of a magazine) that Bob Cauterucio makes.
In addition to the choices Yankee mentions there are some new cartridges which you might want to look into if you are unable to handle the recoil of the 260. There is a 6 mm XC which is rapidly growing in popularity in the across the course (paper punching) crowd which can get to the other side of 3000 fps with a 107 gr SMK and 39 or so gr of H4350 and can be loaded down for everything but the Rams either with a lighter powder charge of around 34 gr Varget or even with an 85 gr bullet. There is factory brass available for this which is properly headstamped and there is a rifle sold with a factory chambering so it should be a "factory cartridge".
There is a .26 (6.5mm) Grendel which is to be officially unveiled at the SHOT Show in Feb. It is supposedly a slightly "improved" version of a 6.5mm PPC and will be offered in factory chambered AR-15s
http://alexanderarms.com/ (perhaps others later). Factory brass, ammo and so on should be available. There used to be a web site of a fellow who was shooting a 6.5 mm PPC in an AR-15 "spacegun" across the course with 128 gr Cauterucio bullets at 600 yards and lighter ones closer. I do not recall the specifics of the velocity, but I think he was shooting the 128s around 2800 fps in a 24" barrel.
You may also have heard of the 6.8 mm (.277") x 43 SPC which Barrett Industries has developed with Remington and a military development team as an upper for the M-16/M-4. It is to shoot a 115 gr bullet around 2800 fps out of an 18" barrel according to reports
http://www.remington.com/ammo/ballistics/centerfire/comp_ballistics_results.aspIt just depends on how much recoil you can tolerate.
Good Shooting