bullets that keyhole = too small in diameter
Don't know what expander you're using to bell your 45acp cases. The factory expander ball is designed for the smaller/shorter jacketed bullets. A lee factory expander (has brass ring/watermark left on it from the 45acp brass) next to a lyman m-die that is designed for cast bullets.
As you can see the lyman m-die is longer & it expands the case deeper protecting the cast bullet's bases.
Some 200gr swc's that I cast/load. Note there's no wasp waist, bullet bulge, no base of the bullet being seen thru the case. The cases are expanded correctly for the .452" +/- 8bhn cast bullet.
Those bullets pictured above, not hand picked/cherry picked target by any means. Nothing more than the test target used that day to test a new nm 1911.
FWIW:
The h&g #68 & #130 cast bullets have been used by countless 1000's of bullseye shooters for decades using 3.6gr to 4.0gr of bullseye powder. 4.5gr of bullseye pushing a 230gr jacketed rn bullet has been the mainstay for the government marks (match) 45acp ammo. 5.0gr of bullseye pushing a 230gr jacketed rn bullet has been a duplicate load for the standard military issued 45acp ball ammo.
If you have to either go to p+ loads with bullseye or hot loads with unique to keep your bullets from tumbling. That's telling you the cast bullets are too small or to hard or a combination of both.