basically the 260 was an interesting cartridge, but it kinda lost its zip as commercial round to me !, .. i guess it could be compared very closely with the Swed, an not all that much better... i've also heard that a 6.5 jap rifle makes for an easy conversion to the 260 with just a reamer if one was interest in making a A-square/260 rem. "not sure 100% on that".., it was put into the factory line-up in the later ninties ?, no doubt its a worthy gun, but comparing ballistics as you say it drives a heavier bullet then the .25, but what you've done in that statement is jumped a hole, of coarse the larger diameter will have a heavier bullet weight, giving need for more bearing surface that would stabilize its flight,.
keeping in the same family of cases i can only think why not just buy a 7mm-08 to replace the 260Rem.,..another hole jump or so !
my thoughts on building the .25 Souper isn't new, but changing it to AI may have a new meaning to me, along with a custom rifle, not a factory chamber, plus the possibly that it could out do most of your .25's is a interesting thought as well, i'm not trying to compete with 6.5's.. although it mite?
there is no shortage of cases to be had, forming cases an having dies made is not a big deal today, also about the long chamber mentioned earlier, it wasn't a concern of mine rather something i had read of another persons idea/worry/thoughts.. i would first consult with both a bullet an the barrel maker on how long the throat should be anyway. i've never owned a 1/4bore so staying in that class, the goal here is that one hopes for better accuracy, a gain in velocity, more energy, flatter trajectory, less throat erosion which can be done by blowing out the shoulder to get more internal case space. hoping for great results, as one would, you'd wind up with a Souper personalize firearm....
