when to trim

[kwatters]

I always trim after I've re-sized the brass. I would assume that working the case would stretch it a bit more although I've never measured to find out.

Trim after resize. Last batch of .223 I ran stretched after resizing quite a bit.

 

[lovemywoods]

I plan to use my Lee classic cast press to reload 223 rem. I will be using the RCBS trimmer, I was wondering if I can trim after cleaning with the primer still in, and then go through the rest of the loading process while using the index feature of this press.

Some of the responses have made it seem that trimming before or after sizing the .223 is just personal preference.

Others have said that you should trim after sizing and have pointed out that the case length grows as part of the sizing operation. This is true.

I think it's important to be very clear in answering your question.
The purpose of trimming is to:
1. Keep the case length under the maximum specification and
2. Achieve a consistent case length to reduce variation and increase accuracy.

If you trim before sizing, you might accomplish #1 but you can't accomplish the second goal unless you trim after sizing since cases grow by different amounts when sized.

You should always trim cases AFTER sizing.