Drop-in versus semi-drop in pistol barrels?

[His lordship.]

Looking at after market custom barrels to add to my various semi-auto centerfire pistols.  It seems that there is the choice of barrels that will fit (drop in) and barrels that will fit only 70% of the time, (semi-drop in) like the Bar-sto made ones.  Bar-sto and CZ both state that their barrels need to be fitted (altered) by a trained gunsmith.  Haven't these people ever heard of interchangeable parts?  This is especially disturbing as these pistols have a military history, CZ-75, Browning P-35, Colt 1911, etc. and the military needs guns that can be field serviced, not requiring to go to a "trained gunsmith".

I have switched bolts on military surplus rifles like Mausers for years, I did not need to hire a special gunsmith to fit it.  What is up with this?

Thanks.   

[Mikey]

Chris:  I don't know about CZ barrels but Bar-Sto is a top of the line barrel.  I have owned Bar-Sto barrels in a number of different calibers and they are quality work.  All mine simply dropped in replacing the issue barrel but Bar-Sto, in particular, makes match barrels for the Marine Corp Marksmanship Unit at 29 Palms and firmly believes that to obtain the best accuracy from his barrels they must be fit properly to the slide, hence he (Irv Stone) always recommends fitting. 

I have no doubt that the barrel will simply drop in and replace the current barrel and function but until it wears in at the edges and mates neatly with the slide when in battery, unless it does that when you drop it in, you might not obtain maximum accuracy. 

Ed Brown also makes quality drop in barrels.

If you have fitted Mauser bolts you can most likely properly fit a 1911 barrel.  jmtcw.