I'm glad to hear someone is trying cast bullets in the 7 TCU. I have tried various cast loads with minimal success. I have a buddy that has shot a bunch of lead in his 10" 7 too. He said that they shot well enough for the Handgun Silhouette course. I never watched them shoot until he sold the gun to another buddy. They didn't shoot chickens at 200 meters at all. That was the new Lyman bullet. I borrowed the mold.
I shoot at a rifle silhouette range twice a week with Thompson Contenders. The first targets are chicken size at 200 meters (220 yards). We have been unable to hit chickens, unless one commits suicide and jumps in front of a bullet.
My best success has been with a Saeco #280 (140 grain gas checked) with very light loads. These loads will provide 50-yard practice loads.
6.2 gr. of IMR SR 7625 with a small pistol primer. 1.5" groups are the average.
I tried one load with 16 gr. of IMR 4759 and a 4 shot group at 100 was 1.5". I don't think I repeated that accuracy, since I don't have any other targets posted with that load.
I have tried the Saeco #073, a 165 gr. dog dick type bullet, without any success at all. The RCBS 145 gr. bullet was awful.
I have some of the new Lyman 160 grain bullet, but I haven't tried them yet.
I would be interested in your findings with the 7TCU.
Harold
