SHOOTALL: I shy away from the 400 Cor-Bon for a number of reasons, it being a less effective 10mm as the main reason. A 10mm will flat outshoot a 400.
The 400 depends on its case design, which is rather poor and is an offshoot of the old 38/45 Clarke design from days past. That case was not designed to shoot heavier loadings and the only way the 400 makes its name is by using very 'lightweight for the bore' slugs and that gives it the high end velocities it claims. Cor-Bon also claims the use of 'special powders' you cannot purchase in typical cannister form. Well gosh, whadda buncha hooey. If you take the 45 acp case and neck the shoulder down as far as Cor-Bon has, and stuff a lightweight bullet into it you can get your 1425'/sec without any real headache or pressure concerns from a number of cannister powders.
I will gar-an-tee-ya that if you load the 10mm case with a 135 gn hp over a hefty powder charge you will get the same results as the Cor-Bon load. But, you can't load the Cor-Bon case heavier than 165 gns and get much better than a pumped up 40 S&W. And of course the factory ammo is scarce. I have a 25 rnd box of the 400 Cor-Bon I bought a few years ago to see if I could chamber the cartridge in my 40 caliber wildcat - nope, a side by side profile comparison told me the Cor-Bon case would split the neck lengthwise and probably cause me serious problems. I'm thinkin' that just for the hay of it I should pull the bullets and powder, load the stuff into my own cases and see how it shoots. Maybe. I might even give ya the box of ammo just to get it off my gun bench.
You also said the Glock was not as accurate as the Colt - yes, that is an understatement but the Glock can be made to shoot pretty well. Much of the accuracy problem is, I surmise, the result of the trigger (and sights maybe) - although I have seen some Glock 9s shoot so accurately that I almost want one, so the 10 should be able to do as well. But, European gun makers don't usually make barrels to satisfy the American shooter's desires for shooting cast bullets, so you may need some 'attention' for that barrel.
I would slug the bore first to determine the actual bore diameter and then consider fire or bore lapping it. Here's why - Marlin, for example, runs the bore size on their lever actions in pistol calibers on the large size and cast loads that shoot great in revolvers may not shoot so well in the Marlin pistol caliber rifles or carbines. The Glock may want to shoot jacketed bullets accurately enough but may not want to deliver any accuracy with cast loads unless they are properly sized. You can lap and 'size' the bore at the same time by using lapping loads sized to the proper diameter.
Let's say your Glock bore actually runs to .402 or .403 in the grooves but the lands are good at .400 - .401. So, your sized .401 cast loads may not shoot accurately in your barrel and some jacketed loads may not shoot well at all and you might have to have cast slugs sized to .403 or even .404 to shoot accurately. You may even have to go in the opposite direction if your bore runs undersized and find the need to size your cast slugs right at .400.
Also, European gun makers do not, I understand, worry about rough bores or sharp edges that might lead to inaccuracy and figure that any roughness will be shot out. Shooting cast bullets in rough bores really almost always kills accuracy but lapping removes the roughness and greatly helps with accuracy and that might help with your Glock.
Do Glock barrels wear polygonal rifling - I wonder if that would effect lapping results.
And, you may have to do the same thing with the Colt barrel but there are many barrel makers who make 10mm barrels for the 1911.
OK, I have to go clean a rifle. Good Luck and hope you latch onto that Colt. Mikey.
