The Armscor M200 and M206 revolvers are visually almost identical to the Colt Police Positive and Detective Special. M1911.org recently reviewed both, and there was effectively no difference in accuracy between the 2" and 4" versions. I agree that replacing the barrel on your Colt will severely detract from its value. If you want a 4" revolver to shoot, get one of the Armscors.
http://ezine.m1911.org/showthread.php?t=140