,,,can't address Glock or Sig, switch barrel guns, but I do have some experience with a Colt Combat Commander, the steel framed version, originally in .45 ACP. As sold to me by a close friend, it came with a Wilson Match Grade Barrel and Bushing, beavertail grip safety, long match trigger and an early version of Novak sights. It was and remains, my #1 1911...other representatives of that storied platform have turned my head, sometimes for months, but that old series 70 vintage Commander remains my 'go to' gun when I mean business..be it BBQ shoot-offs or serious carry when its weight is not a factor.
All that said, I respected the old gun so much that I searched for and found an add'l slide and barrel assemblies in 9mm and .38 Super. While they never perked with the precision of the original .45 barrel, they are useful for practice and most folks that see them, have a hint of lust in their eyes...I've been offered some impressive sums for the gun....NOT GUNNA HAPPEN!
When Ciener was still doing well, I ordered a .22 lr unit for it as well and quickly found that even Wally World Remington Bulk HP Golden Bullet .22's would easily shoot into sub-2" groups, and at 25 yds too. It's a good, cheap practice modification, quiet too, if the neighbors are a concern...
As to reliability, all of them work well, with the .45 the best, nearly 100% if good ammunition is used. The 9mm and .38 Super slides are less than 100% but not by much as is the .22 lr.
It's my favorite gun, and of the 36 handguns in the safe at this point, it is the last that I would part with....try to pry my cold dead fingers off the grips and all that....
Switch barrels make sense...if you can't gunsmith it yourself, get some knowledgeable help. I did mine and have had no real problems. Jerry Kuhnhausen's shop manuals have it all for Smiths, Colts, Rugers and the venerable Colt automatic. For Sig's or Glocks there's a wealth of info on the net...get in there and do it pard...you'll enjoy yourself and dazzle your shooting pals.
Best Regards, Rod BTW, here's the apple of my eye, complete with all its slide and barrel assemblies. R.
To Hunter Customs
...can't say if my Commander has been milled or not, tho it doesn't look like it, and I bought it used from a friend. I did smooth the feed ramp with a dremel, and changed the ejector, ...but it was 15 years ago and as I haven't changed the ejector since...may be a 9mm or a .45, can't say. Other than that, and some minor fitting on the link as is normal, no changes were made. I will say that the 9mm and .38 Super have a dedicated recoil spring..don't ask me what strength...it's been in there of over a decade and a cpl thousand rounds. I do use Wilson's recoil buffer and have had no problems. Rod