Why trim the cases?

[dblb]

Hey ALL,
Just a quick question. (Not new to reloading, all straight cases tho) Why is it
necessary to trim the 5.7 to a given length? After sizing in LEE die, they pass
the Sheridan GO/NOGO test and chamber in my pistol, just the case alone.
Tried the search but no results. So here I am. Thanks for your help.
Bob

[Rapier1772]

Because they stretch. You might get away with one reload or maybe even two without trimming but check the case length, they're longer each time; this also goes for straight cases. If you don't already have dial calipers then you need to get some & make sure you are staying within tolerances.

One way to ruin your day at the range is to not be able to shoot because your ammo won't chamber or worse, jams when it does.

[panzermk2]

Or worse chambers just enough for the firing pin to strike the primer and have a section of unsupported case exposed.