Just curious at what length you fellows start trimming cases back for your AR15 brass?  I just measured out about 300 cases last night and separated about a dozen cases that went over the 1.76 mark.  None of then were over the 1.82 mark.  An acquaintance of mine that reloads 5.56 says that he never trims and the case will split before it gets too long to use in an AR15 chamber.  I'm not sure what to think.  I've always played it safe and done the max CL and max COL "by the book" in terms of AR15's.

Thoughts?

Max case length is 1.760, if it's longer or close to it, trim it.

i usually get 2 fires before trimming. i trim anything that is close to 1.76 and i trim to 1.75.

lately i have been trimming after every firing because i got the dillon 1200 that sizes and trims all at once much easier than having to measure every case.

not trimming or keeping your cases under the max is very bad practice just because someone gets away with it dosen't mean everyone will and i don't need a kaboom in my face.

OP,
I understand why your friend telling you this. The current 5.56 nato chamber has a little extra lead and what he is telling you very well may be true. Some people make a casting of their chamber to get a precise measurement on what the max case length for "their" chamber is. There may be some "method" to the madness but for all of us normal folks the above statement posted by BIGGDAWG that I highlighted in red is the rule to go by.

When it comes to hand loading there is only a small number of things that can cause a dangerous overpressure situation. A over-length case is one of them.

Trimming is an important safety step.

I trim every case every time I load it.  I did so before when I only had a Forster trimmer and it sucked but I did it.  Now that I have a Giraud and a Dillon trimmer it is much less annoying.

Actually the chamber dimention "base to case mouth" is the same for the 223 and 5.56, 1.7720 with a few exceptions .

steve,
You are absolutely correct. My mistake. I was thinking free bore and got the two mixed up. I should post after sleeping and not before.
The "extra lead" that I wrote about has nothing to do with max case length.

Keeping your brass at or under max length is a must !!!

I trim all my brass to 1.750...it takes too much time to measure and sort so I just run every piece through my little possum hollow trimmer.

Yep.  I feel the same way.  Too damn much work to measure.  Run each piece through the PH timmer and de-bur if required.  A lot faster.

A very few cases will be a bit shorter than 1.750 - but if its not match ammo it probably won't matter.