Well, the wait is over with somewhat surprising info! "Bigngreen" got my 338 Sherman together and between himself, a friend, and his dad, "Cmantha", we have some data. The initial results with RL26 were not what I had hoped for. Even though you could get enough in the case, it seems the bore size does not produce enough INITIAL pressure to make it work. It never did pressure out but velocity increases with a several grain spread were unusually low! (normally 50' per grain). It reached the mid 2700's but increasing the charge neither pressured it out or increased the velocity much!
Now for the good news! Cliff loaded up some 250 Bergers with RL17 this morning and things started happening. The pressures increased consistently with each grain increase and he reached a node near the top where a 3 grain spread shot in about 1 1/2 " at 100 yards. His top load fired was 62.5 grains which reached 2802", "IN A 24" BARREL FOLKS", and Cliff said he felt there was a little more left!
This is super exciting for me and especially since we can do it with a faster burning powder. I think this may bode very well for the new RL16 which I have on the shelf. It is supposedly just a touch slower than 17 but is VERY temp stable. Also, I now believe that N560 may have a lot of potential with the 250's.
It also looks as if 3150', or more, is possible with a 200 grainer. We used both Norma and RWS brass for the test and have plans to try PRVI with another build coming soon from a certain forum member. His barrel will be 26", but I will leave his story for him.
I believe the potential for this round is unlimited with all the old '06 sized actions laying around! Can you say 4400 ft/lbs.
Initially I was thinking of this round as a closer range elk and bear thumper, which it will be. I now am seeing serious long range potential with the 250 Bergers at around only 24 moa at 1000 yards!
There will be more data coming, hopefully not too far off, since I am in the moving process AGAIN! ...........Rich
