Use Filler on top of powder
I've been loading over 45 years now and when I started shooting silowet with a 357 mag. revolver and after a Thomson Contender. I cast at the time my own bullets 158gr SWC, using Unique 7.1gr.. It was not a hot load at all but got the job done. I used a fill over the top of the powder to hold all to the back of the case on the primer. Worked great.
Back then several loading manuals even talked about it. I don't see that anymore but still use the filler.
Does anyone else out there use a filler? The filler i'm talking about is the filler they use to make quilt.