450Bushmaster.net

So, i appreciate that this is an old post, but seeing as i was looking for the same info and as near as i can tell does not exist on the internet, i decided to update this post.
I am shooting 450 in a Ruger American and AM seeing the brass grow by small amounts each sizing operation. What i have found is that L E Wilson case holder for a 45-70 (fired case) fits almost perfectly. I say almost because the head of the case is within the case holder, but the tailpiece of my trimmer is smaller than the case, so all works.
Hopefully this helps the next guy

I recently found that I had some long cases and ended up trimming about 35 cases. I had ignored measuring case length for a long time due to everyone saying the cases get shorter. I used the Lee cutter and lock stud, it's simple and cheap. Some of my brass was bought once fired from a prominent company from their test loads, so I don't know what abuse it took.

Yeah I've had an issue with case length growth. It only happens in my Tromix barreled upper, with Starline brass (1 or 2 firings), and loads that are a bit warm. Nice thing, though, case head growth isn't an issue. I trimmed them all using the Lyman Universal Case trimmer w/pilots. Not a great trimmer, but I only use it for quick, or small batch trimming, when I don't feel like setting up one of the nicer trimmers.

Loading to AR pressure tolerances, my brass always shrunk a little except when I pushed them hot, the cases either didn't shrink or grew a little bit. I wonder if despite the bolt action chambers being up for the additional pressure, whether the brass isn't. While this caliber originated with the .284 Win, the 450b brass is a little skimpier on the walls out beyond a little bit past the web. Many moons ago, I put up a graph of the wall thickness difference between the two, measured every .1 inches back from the mouth, as far as I could get my calipers in. Now I have a wall thickness micrometer. I may revisit that for anyone who's interested.

Hoot