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Yeah, but...you're assuming the original barrel was any good. On an RG...wow, I wouldn't bet on it.
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True that, but I forgot to mention that we ran a baseline test with both revolvers with handloaded ammunition, and the velocities were close.
Consider this for a minute.
Assuming that velocity increase with barrel length is hypothetically linear...
With a 5-inch 1911 barrel, there is approximately .900 inch of chamber and 4.1 inches of rifled section. Let's simplify it and just call it 4 inches even.
If we assume 35 fps gained or lost per inch...which is pretty close for standard pressure .45 Auto and 850 fps mv...we get 140 fps of the total in the barrel. When/where was the other 710 fps produced?
If we then assume that the missing velocity was produced in the first half-inch of bullet acceleration...we gain about 122 fps in the remaining 3.5 inches of barrel...and 728 fps in the first half-inch.
Later, I ran another experiment with an old, badly pitted 1911 barrel by boring it out to a full half-inch ID all the way to the chamber shoulder. I didn't use a chronograph, but instead compared penetration depth in dry newsprint with the depth before the barrel was altered. The unaltered barrel, firing the same lot of ammunition...230-grain RNJ with 6 grains of Unique...gave a tick more than two inches more penetration than the bored barrel...and the bullet from the bored barrel gave indication of a slight yaw.
And, yes. The slide cycled at what appeared to be normal speed, and the empty case landed at about the same distance from the gun. If anything, in the test with the open barrel, the slide's cycle felt more brisk, and seemed to hit the impact abutment a little harder.
In other words...hardly enough to flip a coin for the practical difference.
With one of the quicker powders like Bullseye...I'd be willing to bet that the unaccounted for velocity is realized before the bullet base clears the case mouth.