Trimming?

[ilovepotatos]

You haven't stated yet whether or not you've ever gotten the case removed to examine it. In fact your initial post says it's still inthere. As there is usually a bit of leeway in a chamber how did you conclude that it was case length rather than en excessive load that froze it up?

Because I have several other casings that are all from the same batch. All too long.

 

[tiriaq]

But that doesn't necessarily mean that the cases are jamming at the end of the chamber. Military chambers tend to be generous, and just because a case is over spec., it may or may not be too long for a given chamber. By all means, trim your brass to recommended length, but when you inspect the stuck case, just make sure that there is not another reason for the case getting stuck.
Incidentally, a loading manual may be a better source of information than a friend.

 

[savagefan]

You can never have too many books.

 

[Gunnerlove]

Skip the Zip trim, buy yourself a good variable speed cordless drill instead. I throw mine in my range box with a bag of deck and self tapping screws for when target frames start falling apart.

 

[tiriaq]

Did you ever get the case out, and determine why it was stuck?