Bullets backing out of case...thoughts?

[8x68s]

Not happening to me but I have heard of it happening. Specifically in a very full or powder crushing load. (Not recoil induced.) What is the cause? I'm wondering if powder has "spring back" capability or is it the trapped air in the cartridge case expanding as one goes into higher elevation locales? What got me thinking about this is the expansion and contraction of empty water bottles coming and going to higher elevation hunting areas.

I look forward to your opinions... thanks!

 

[SO I HUNT]

I think neck tension may part of this problem not sure

 

[Dean2]

A compressed powder load does exert pressure on the bullet. If it is compressed enough it will push the bullet out of the case, especially with a little vibration like travelling in an MTM case. You either need enough neck tension or a light crimp if making compressed loads. That or shoot them right away.