I have an older 1873 carbine chambered in .357 magnum. This rifle cycles my dummies fine, and will cycle through actual rounds at the range (not firing). But when firing the rifle it will occasionally seize at the bottom of the downstroke of the lever and lock up. I will admit that the cartridges are near max at 5.7 grains of Unique with a coal of 1.54. It does not appear that the stop tab is bent in any way. I am now out of Unique but have plenty of Bullseye. Should I start with say 20 or so cartridges at the start charge of 4.3 of Bullseye and go from there? Is it possible that the action is getting too hot? I am loading 158 grn Bear Creek bullets. This rifle has an aluminum carrier and is short stroked.