One thing I did when I had mine converted to a 458Lott ... give the 'smith dummies loaded with pulled 510gr Winchester softs. If they can get that projectile feeding reliably, just about anything will feed.

Shame about the Winchester soft too ... its a magnificent projectile for soft skinned game like Sambar. I used to pull them and replace with a 480gr Woodleigh to get the factory ammunition feeding reliably. Worst scenario in a BGRC shoot had 3 of 5 (one magazine) fail to feed ... always from the left from memory.
Cheers...
Con