I doubt if there is anyone alive today with experience with this type loading but have at it. Everyone is welcome.
As you can see by the picture of the chamber cast the neck is the same size as the bullet, .257.
The case capacity in grains of H2O is 57.6, a .250-Savage is 47 and the .257 Roberts is 57.2.
I can adjust the length of the base-band by using different thickness of washers when I make them and I can also shorten the case neck in the case trimmer.
I have been shooting with the case just touching the back of the bullet and have used floral-foam, thin and thick cork as well as IPCO wads. It seems to like the thin cork wads the best.
If I put a Base-Band bullet into the chamber and fire just a primer it completely seals the bore and after 15 seconds when I open the rifle the MT case will shoot across the shop.
With the bullet ahead of the case, ala Schuetzen, and the high pressure the wads are very liquid one moved all the way down to the shoulder before the pressure trapped it and indented the case.
I started at 100 yards then quickly moved back to 50 to keep the bullets all on the same target. I have over the last two weeks gone from 2 groups to well under an inch at 50 yards and time to move back out to 100.
A load that works one day seems to fall apart the next. Im now cutting off the case in order to seat a Sierra 75 without a base band and will see how that works.
Like I said before I had one case start to separate and am clueless why.
