Critical Dimensions?

[brokfut]

Bought new 338 win mag brass last week and the Sierra Reloading manual says the case length is 2.500 inches and trim length is 2.490.
Just how critical are those numbers? I ran all the cases through the RCBS 30-338 sizing die and they all were nearly perfect at 2.500. I trimmed them to 2.494 but, really, do I need to do more?

 

[VikingsGuy]

In general case length is important to safety, but since you were within spec it would have been ok to use at 2.5000. I typically trim new brass just to make it uniform - I measure a bunch and then trim all to the shortest length (assuming shortest is still in spec).

 

[std7mag]

It will be more critical to watch after you fire it.
Max i can go between trimming is 2 reloads in my 7mm Rem Mag.