My drilling is a 9.3 x 72r, nitro proof, and it works just fine.I use swaged .358 bullets, 200 grs, and bring them up to .363 dia. and I've kept the shape very similar to the RWS factory shape. I must admit that I rarely take shots past 100m though. I either let the bugger go or stalk closer. Dead is dead and if you are prepared to be careful with the shot, the old '72r knocks them flat.