So I picked up a Lee Enfield No 4 Mk1* 2 groove awhile ago. Bore is bright and shiney and it is overall in very good shape. I have been struggling to get it to shoot cast. I am using water dropped coww for my alloy and powder coating the boolits. I started with the Lee 312-185 sized to .314 and they tumbled. Took a step backwards and ran about 40 rounds of factory ammo and the thing is a tack driver. So I knew at this point it is a very capable rifle. Decided to bump the 312-185 up to .316, still tumbled. For those tests I was using loads of 10g Unique and 13g of red dot since they both have seemed to shoot well in any 30 cal I've used. I did some research and digging and got my hands on a Lyman 314299. Was lucky and got one that drops .315 as cast. I add a gas check with my .314 sizer then add 2 coats of PC to get it up to .318. These loads showed some real promise and did not tumble. My best groups came from a load of 12g of unique and another load of 17g of 2400 (picture of this group below). Before I got my hands on the Lyman mold, I ordered a mold from arsenal (311-176 LFN) and had them bump it up to .315. It's a beautiful mold, but they accidentally made it a plain base instead of a gas check. I didn't discover this until I had started casting with it. Since I already had some cast, I figure I would powder coat and load some up. I did 3 loads of Unique (11g,12g,13g) and 2 loads of 2400 (16g,17g). To my surprise, I had quite a few tumble and keyhole (picture below). I could use some help understanding why the arsenal boolits tumbled and the Lyman did not? I don't have a chrono, but based on load data, the arsenal were probably going a little slower. Have a picture below of the 2 boolits side by side. Any input or thoughts would be appreciated!