What causes key holing in sub loads

If I can push 60m reliably with a sub load I'll be happy
Just like my .22lr but bigger

At the moment with ballistic tips it's brain shots only @ 20m or less

You have a lot to learn. I recommend that you read the stickies on castboolits.gunloads.com .There is several years of reading there ,in particular look up the posts of Larry Gibson and rpm threshold. I shoot a 200 and 220grain boolit subsonic to 100 m with a 1.5/2.0 inch group (mostly) 1:10 twist powder coated or lubed with Bens Red (lithium based lube) .so it can be done and is a lot of fun.

Too slow a twist for that bullet. Need a faster twist, more MV or lighter bullet. No shortcuts are going to fix it.

Try 10 grains of trail boss. On the flip side a tumbling projectile is still going to kill. Expect to go for head and neck shots inside 100 yards, anything outside of this use a a standard load.