CIP/SAAMI measurement of the entire case in 6.5CM is 1.920. Many of my fired cases after FL sizing have 1.921-1.925. If I decided to skip the trimming in case of 0.04 divergence, what kind (if any) impact would it have on my groups? At what range would the group start to open up? I know that reloading is about consistency, so should I trimm the 1.925 brass to 1.920 in the name of consistency?
Trimming the brass- does it make sense in my case?
- Thread starter Oldmauser
- Start date
It will not directly hurt your groups, but it could make your gun not function. The max length is to make sure the neck does not bottom out in the chamber. If your brass did bottom out on the neck, it could either cause your gun to to chamber (best case), or could cause a pressure spike (case neck squeezing the bullet, extreme case). There are ways to measure the max length of the brass for your gun, but it is likely easier to trim your brass.
The trim length of 6.5 CM is 1.910", and I normally aim for the middle of trim and max length (1.915"). Anywhere between 1.910" and 1.920" will be accurate and safe.
The trim length of 6.5 CM is 1.910", and I normally aim for the middle of trim and max length (1.915"). Anywhere between 1.910" and 1.920" will be accurate and safe.
I have no idea at what point not trimming will have an impact on your groups or when they'll open up, but consistency is the whole enchilada really.
There are enough variables in play already, no need to make more. Keeping your brass within spec will keep you within a reasonable repeatable range, if you're lazy about it (like I am) you can just take your cases down to minimum (1.910") and get at least 5 firings out of them before having to trim again.
Honestly for best accuracy, and consistency is accuracy, trimming every time is probably best (one less variable). I probably need to stop being lazy and trim every time hahaha!
If you get an easy to use trimming tool, it's not that bad.
The easiest way to do this is set up your trimmer for a certain length (as others have said aim for halfway between min and max saami spec) and then just run all the brass through. If it gets trimmed, it needed it. If it doesn't, then it's still good. Either way you know for sure that your case isn't too long.
The easiest thing to do is not trimming all the time. I can not tell you the satisfaction that has come with not taking my brass to the trimmer, then chafer and deburr every reload. The length of your brass varying a few thousandths is not going to effect anything.
You should always trim cases that are over max length. Since the max for 6.5 CM is 1.92, all of those need to be trimmed. I would not trim back down to max, because then you'll just need to trim again after the next firing. I would trim to the trim length, 1.91, or somewhere in between (maybe 1.915 like some have suggested).
