CS86, this should not be the case. Unless you are shooting a VERY old gun, where quality control was not up to modern standards, the bore diameters should be almost exactly the same.
Now, you CAN measure your bore diameter at the muzzle with a dial caliper--which is what I suspect you're doing. However, the best method is to slug the bore.
Here's how: get a SOFT lead bullet that is slightly over the diameter of the bore. You don't necessarily have to measure the difference, a calibrated eyeball will do here.
Since you have semi-auto pistols, the job will be simple. I would use a .45 rifle bullet, sized around .458. Make sure you're using a SOFT lead bullet.
Remove the barrel, and place it muzzle down on a non-marking surface. Lube the bullet well with a light oil, then use a close fitting NYLON punch, or hardwood dowel to tap the bullet through the chamber. Drop it in, and tap it through the muzzle.
However--with any modern 1911, this step is unnecessary. If you cast bullets, a good all around bullet is the 200 grain HG 68 design semiwadcutter. Lee makes a 6 cavity version of these molds. Get a sizing system--I have both RCBS and Star lubrisizers--with a .452 sizing die. I size them and lube with Javelina Alox, on top of 3.8 of Clays for target shooting; 4.5 of HP38 for general practice.
Hiding in plain sight...