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In my experience I found that straight wall cases grow. If you think about it they expand to fill the chamber just like bottle-neck cases. When you run them through a sizing die you squeeze the case back to size and some of that expanded brass flows to the mouth.
I don't even check cases with calipers anymore. My trimmer is fitted with spacers that limit the trimming to the length I selected when turning the spacers. I set the trimmer to trim the shortest case (9mm) to 0.75" and made the spacers to trim each case to a certain length. No adjustments are required.
With 9mm, 38, 357 mag, 357 max, 40 S&W, and 45 Colt there are always more cases that trim than those that don't.
I trim after sizing because that is the length that goes in the chamber. I counted the cases that trimmed and those that didn't in 9mm, 357 mag, and 40 S&W and found that between 50 and 60% trim to some point. Some just to square the mouth and others up to several thou.
I doubt I would ever notice in my 357s but the 9mm and 40 have caused failure to go into battery before I started trimming with every reload.
I suggest you measure your sized cases to see if the lengthen or not. My experience shows they all get longer.
 

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In my experience I found that straight wall cases grow. If you think about it they expand to fill the chamber just like bottle-neck cases. When you run them through a sizing die you squeeze the case back to size and some of that expanded brass flows to the mouth.
I don't even check cases with calipers anymore. My trimmer is fitted with spacers that limit the trimming to the length I selected when turning the spacers. I set the trimmer to trim the shortest case (9mm) to 0.75" and made the spacers to trim each case to a certain length. No adjustments are required.
With 9mm, 38, 357 mag, 357 max, 40 S&W, and 45 Colt there are always more cases that trim than those that don't.
I trim after sizing because that is the length that goes in the chamber. I counted the cases that trimmed and those that didn't in 9mm, 357 mag, and 40 S&W and found that between 50 and 60% trim to some point. Some just to square the mouth and others up to several thou.
I doubt I would ever notice in my 357s but the 9mm and 40 have caused failure to go into battery before I started trimming with every reload.
I suggest you measure your sized cases to see if the lengthen or not. My experience shows they all get longer.
Not in mine. I have not had to adjust my crimping dies one bit which would be the case if cases were lengthening. Over time as you reuse cases, the base will widen out to the extent that the chamber allows it. You aren't running cases all the way into the sizer, only that part of it that is above the web, and because that base web area gets hammered by pressure every time you shoot it, cases gradually become shorter. The .45 ACP is well known to get shorter over time, and since even brand new cases are a bit shorter than spec, you never need to trim them.
 

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Our experiences are very different. Use whatever works for you but I have never seen a case get shorter with firing.
 

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Our experiences are very different. Use whatever works for you but I have never seen a case get shorter with firing.
When I do trim mine (rifle case almost exclusively) I like to trim that about 2 thousandths below SAAMI minimum. For the ones that sometimes need trimming, I have made gauges for the by cutting the proper size "notcher" in the handles of old butterknives that I pick up at goodwill or yard sales. I keep these on a large key ring and it makes it very easy to run a check on case lengths. I cut these notches to be about 2 thousandths below........................... As you said many experiences are different and we need to use whatever works best:)
 

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You should trim after sizing. The sizing process will make the case longer.
You can use the "trim to" length if you like but you can also measure the chamber and trim to match your chamber length. I use my chamber length minus 0.001" for my trim length.

Other than that your checklist looks great.
Thanks - I double checked the sequence and thanks for the catch! I reordered the sequence to show check/trim after sizing.
 
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