The bearing surface of the 45 Colt is approximately 15% more than the bearing surface of the 44 mag, thus the Colt 45 is acting against more friction with the contact of the interior of the bore than the 44 mag. How much does that off-set the 10% larger surface area for pressure to act on of the rear of the 45 Colt bullet?
Negligible. Peak chamber pressure generally occurs about the time the bullet breaks neck tension and jumps to the lands. As the bullet moves down the bore the volume of the combustion area is rapidly increasing with a corresponding decrease in pressure. Generally every time the combustion volume behind the bullet doubles the pressure is cut in half.
For the sake of this argument you can't make any value statements that are valid unless you have the following:
1. Bullets made of the exact same material and constructed identically - the only difference being one is .45 cal the other is .429 cal.
2. The cylinders must have the same amount of clearance between the chambers and the OD of the loaded rounds.
3. The barrels must be the same length, identical metallurgically, and rifled as close to identical as possible.
4. The throats have to give identical clearance to the bullets.
5. Then you could pull a bullet through each bore to determine if the coefficient of friction is identical as you claim. Absent the above, you can tell the world the difference is negligible, but you wouldn't know if you were right or wrong.
