I was talking to an old co-worker at the rifle range about Improving My groups @100 yards with a 22LR. Anyway He told me to Weigh My 22LR ammo and sort them by weight. Does anyone here do this and does it improve your groups I know that Constancy is the key .

by weight,and then by rim thickness. rimfires headspace on the rim. It easy to do but time consuming. 223 brass case trimmed and squared deburred no need to size. Drop in 22lr, measure with calipers, record and seperate, repeat. shoot. Sometimes yes, and sometimes no. Try it. does't seem to matter much in my 39A. SEEMS to matter a little in my anschutz target rifle. grounds squirrels don't the difference!!!!!! OH, and by the way my old 39A is far more accurate than my anschutz.

Thanks for the info MyAliyah.  

You can buy a .22LR rim micrometer from target shooting supply houses like Champion's Choice.

www.champchoice.com/detail.php?item=CC1200
CC DIAL INDICATOR RIMFIRE GAUGE, item CC1200

This is worn around the neck on a lanyard while in use.  This prevents the .22LR round from firing if the gage is dropped, WHICH IT WILL.
Using this gage, you sort ammo in lots, which gives better accuracy.

Wow the stuff people come up with I had no idea that there was such a thing as a DIAL INDICATOR RIMFIRE GAUGE.  So how do I find the ideal length? Tm getting a little confused here.

Quoted: Wow the stuff people come up with I had no idea that there was such a thing as a DIAL INDICATOR RIMFIRE GAUGE.  So how do I find the ideal length? Tm getting a little confused here.

As noted above, 22lr. are headspaced by the rim. In some instances, sorting can cull out discrepancy s.
Chamber, ammo consistency, your tolerance as to what to do with what is sorted, all play a roll. The best ammo I have used shooting 22lr. has needed no sorting and therefore no waste, no 'lots' of your lot. Just an ammo lot, all of which is consistent. Finding the right or close ammo for your rifle really should not include sorting. That should come in the form of finding good ammo. Sorting poor ammo is a waste of time in my opinion.
Some may sort the 'right' ammo, having found a lot they like and are willing to take farther. I don't and don't think that this was your question though. Correct me if I am wrong.