Here are some photos of Colt barrels you can use for reference...
https://www.milsurps.com/images/impo...20425203-1.jpg
https://www.milsurps.com/images/impo...00022JPG-1.jpg
https://www.milsurps.com/images/impo...01105JPG-1.jpg
https://www.milsurps.com/images/impo...2045B15D-1.jpg
https://www.milsurps.com/images/impo...01147JPG-1.jpg
https://www.milsurps.com/images/impo...20barrel-1.jpg
https://www.milsurps.com/images/impo...arrelJPG-1.jpg
