I am using 3 different bullets and the same brass, powder load, primer, and die settings. For the Cutting Edge 450/420 grain bullets, I have loaded 3 times without trimming. For the Barnes 450 grain bullets, I had to trim after the first loading of new brass. The Barnes have to be seated much deeper and all shoot to the same point on the target.

So, is excessive pressure from deeper seating making my cases grow? Bolt lift is easy and no blown primers, seating of primers might be a little too easy.

What am I missing? Why do only the Barnes make the cases grow?

Thanks for the help, straight walled cases are new to me.

I am not sure about the deeper seating but heavier bullets of just only 50grs will cause much higher pressures in the Lott.I can tell by the ease of primer seating when pressures have reached too high.Are you using Barnes TSX or the old Barnes? The old barnes could cause higher pressures but I am not sure of that too.If the CE bullets or any monometal bullets are slightly undersized for your bore,then I suspect that can cause lower pressures and bad accuracy.

Higher pressure more case stretch. Deeper seating can increase pressure. I load my .458 Lott a bit on the light side for longer case life.