Do bullets expand as they are seated?

[David Sinko]

I was loading some Cast Performance 330 gr. LBT bullets for the .45-70 Marlin Guide Gun. Due to the dimensions of the ogive of the bullets, overall length of the loaded cartridges is critical or they will not chamber. I trim all my brass every time it is used and I have realized that I do not have any problems when I use R-P brass but when I switch to W-W brass the rounds will not chamber. The ogive of the bullet is actually hanging up in the chamber and preventing the lever from closing. This is obvious from the bright ring around the ogive of the bullet. How can this be? The .45-70 is a slightly tapered case and there is no shoulder to get in the way. A shooter told me that if the W-W brass is harder and/or thicker it will actually squeeze the bullet hard enough to cause it to expand just enough that it will prevent the round from being chambered. Is it possible that cast or even jacketed bullets can expand during seating and cause chambering problems? I have never heard of such a thing but I don't have any other explanation.

Dave Sinko

[wide45]

Take one of the rounds that won't feed, pull the bullet and mike it.