I have shot 45s almost exclusively for the past 1-2 years and shoot the 40 some. The ventliners wear faster the smaller the caliber. I'm not convinced that it is all due to increased pressure but it may well be - what else could it be? Bushings wear out faster also, of course. Hi quality bushings are a must. Possibly ceramic or pure carbide may be the final answer. The one 375 cal smokeless MLer reportedly went from 0.031" to 0.035" in 12 shots- this was a RW ventliner! Try to get consistent groups with that wear rate! This was with slow powders. So plan on spending some money on 2-3 breechplugs if going with bushings and learn to replace them yourself if you don't know how already(I didn't until RB taught me). I like the ventliners on the 45s but have hopes with my M&M high quality bushings. The 69 is 0.031" and the 68 is 0.0292" which I prefer for higher pressure operations(most 40 loads and some 45 loads). The 45 loads are in the hi 30s and low 40s. The 40 loads are in the low to mid 40s or higher. The lone 375 has been shooting in the 50s and 60s. Hopefully, a little more load development will bring it down into the 50s. Just some thoughts.