I've been reloading since I was a little kid (literally)
…and I don't think I've ever trimmed a pistol cartridge case. Least not one that I wasn't turning into something else, or a rifle case shot in a single shot pistol. So I would say it's not crucial. 
Complete thread:
- Reloading -
Art,
2013-09-25, 19:18
![[*]](themes/default/images/complete_thread.png "Open whole thread")
- JimT did an article - Paul, 2013-09-25, 19:58
- I usually trim the cases for semi-auto pistols once -
Hobie,
2013-09-25, 21:25
- I've been reloading since I was a little kid (literally) -
cas,
2013-09-25, 21:28
- I've been reloading since I was a little kid (literally) -
Lee J.,
2013-09-25, 21:53
- I've been reloading since I was a little kid (literally) - Art, 2013-09-26, 06:52
- I've been reloading since I was a little kid (literally) -
Lee J.,
2013-09-25, 21:53
- I usually trim the cases for semi-auto pistols once - Lee J., 2013-09-25, 21:34
- I've been reloading since I was a little kid (literally) -
cas,
2013-09-25, 21:28
- Reloading -
Lee J.,
2013-09-25, 21:25
- Reloading - Bud, 2013-09-26, 08:08
- Triming handgun cases - Charles, 2013-09-26, 10:46
- I've never trimmed a 9mmP case.... - JD, 2013-09-26, 14:35
- I once did some experimenting with 9mm lengths.... - Harry O-1, 2013-09-27, 07:51
- Been reloading for years . . . - Kentucky, 2013-09-27, 09:18