Were there any changes in the lot#'s of any of your load components? If not, I would confirm that it is actually the load that is the problem. When I have had this happen it has almost always been the the rifle. Typical causes have been loosened scope mount components, loosened bedding screws, scope problem, bipod, or barrel wear. If you had checked your bullet seating depth to the lands, I would recheck it to make sure it is the same. When my groups opened up on my 270WSM it had increased a little less that an eigth of an inch from throat erosion. This occurred at 700 rounds fired and caused my groups to open about the same degree as yours. I recently went through a situation with my 300WM that would shoot .25-.5MOA very consistently. I had been shooting with a Harris Bipod and switched to an Atlas. When I first set it up using a Triad Tactical pic rail it shot the same as the Harris. I switched the pic rail to a Seekins mount that had an itegrated sling mount and was a a much sleeker design. The only problem was that the fit between pic rail and the mounting system was a loose fit causing a small amount of wobble. This was enough to open my groups up to +1MOA. When I switched hack to the original Triad rail which had a solid fit, my groups returned. Sorry for the ramble but I had experienced this quite a few times over the years.
