My friend has had one for years and has worked thousands of loads. I have helped him and shot many rounds from his gun. Accuracy that I like has never been there. Hunting accuracy ONLY that would limit range.
I just had the opportunity to work loads for one myself. The first thing I found is that loads need to be near or at max before they will even fire and a hang fire can appear at anytime.
There is no steady progression to tight groups as the charge is changed. When you think you have a good load, the next group will be all over the place.
Even with max loads, every recoil is different. Weak one time and wrist twisting the next. Fliers are common.
My opinion it that it is the stupidity of using a SR primer! I have tried about all of them now and even the mag primers do not change recoil feel or fliers.
Moving to the .460 case, it uses a LR primer and is what the .454 should use. If I had a .454, I would buy .460 brass and cut it down.
Has anyone done this? Please post results.