Final Update. Untill something changes i suppose lol
I decided to try Suprformance again in my 6.5CM, this time with magnum primers and a higher load ladder, so i decided to try the same thing with my 250AI. Playing with quickloads the 143eldx, and the 115bergers, leave the same useable capacity in both their respective cases when loaded to the correct length. I decided to go ahead an use the same charge weights in a pressure ladder from just below book max (i had previously gone up to book max in the CM) on up. They also produces similar pressures according to Quicloads, but really i just needed and easy starting place. Surprisingly they seem pretty similar in terms of pressure/performance.
The highest charges produced primer flattening and velocity beyond what the 6.5CM was getting as "book" max (my barrel is 2" shorter), but no other pressure signs. The CM & 250 cases looked nearly identical at each charge step, which suggests in my very limited opinion and at least my pair of rifles, produced similar pressure levels with these loads. Velocity for the CM was 2800avg on the last charge step, and the 250 Avg 3140 with an ES of 5 if i remember correctly.
Im guessing these loads are about 1/2gr high, tho again besides a flatish primer and velocity im seeing no pressure signs, im going to back off a bit and go shoot a box worth from both guns before calling those my loads.
Accuracy from both rifles was excellent even with the MS' bayo attached to the barrels, groups probably averaged .75 or better.
The in the pictures the first one is all of the CMs 14 -15 rounds (lost a few while i was moving stuff around the truck). The first 10 were not chronographed and most went into the same group on the right side of the target dot, which is about 1"
The other picture is two groups shot with the .250 and two different load levels and one with the bayo on the other with it off, while poi changed avg size seemed to stay pretty much the same. Group near the dot is my new 7mag load.
All in all im very happy with the way this turned out. After I get some time to go out and shoot all of my guns at longer ranges ill do a full report on them and the loads used, but for now these two are pretty well set.