1) drop a bullet in the chamber. Measure the distance from muzzle to bullet nose while bullet is lightly pressed into barrel lede/lead/rifling.
2) measure distance from muzzle to breech.
3) Subtract bullet distance from breech distance to get max COL
4) Load a dummy inert round (no powder or primer) with bullet to max COL.
5) Does dummy round fit in magazine? IF not, seat deeper until it does fit
6) Does dummy round chamber easily? If not, blacken the bullet ogive and case with Magic Marker or Sharpee.
Drop in barrel, rotate case back-and-forth a couple of time.
If scratches are on bullet, Seat deeper until there are no scratches on bullet. If scratches are on case by mouth, you need to remove more of the case mouth flare/belling.
Once you have the round chambering correctly, reassemble gun, place inert dummy round in magazine, insert magazine, pull slide all the back and release. If the round chambers, you have your COL for your barrel and your bullet.
All barrels are at least somewhat different in dimensions and my COL may not be ideal in your gun(s).
However, one thing I have noticed, most bullets are set at a "good" COL when the round simply looks right.
Also, most 1911s are chambered to allow rather long COLs.
I have attached an image of a 9x19 round with a 115gn L-SWC to show the type of COL that is best for most 1911s.