"Drop-in" Conversion Barrel question

[S.P.F.]

Most every conversion barrel out there, Storm Lake, Lone Wolf, etcetera...says their product is "drop-in", but "may require fitting in some cases".

My question is this....

Is it always obvious when fitting is necessary?

I mean, if you install the barrel, and everything works smoothly, the slide goes into battery with ease and no gaps, and everything is perfect looking, is it good to go?

Or instead, must you actually perform specialized inspection, such as headspace checking by a gunsmith, BEFORE you fire off round #1?

I look at the expended cases after shooting, and it all looks normal. I am just wondering if I have been extremely "lucky", but should still have a thorough gunsmith checkout on my conversions.

[tonyxcom]

If the gun goes into full battery then its ready to shoot.

[twotacocombo]

If they manufactured it properly, there should be no fitting required. The outer dimensions should be identical to the stock barrel, which is the only thing that would need to 'fit'. Most automatic pistol rounds headspace off the case mouth, so unless the chamber is reamed incorrectly, there's nothing else to really worry about. You may have extraction problems if the new caliber is much smaller than the original, such as with a 45 to 10/40 conversion, but that's not really a function of the barrel.

I'd say if you can chamber a round and it's held tightly in the chamber with no visible movement, and it extracts reliably, you're good to go.

[dfletcher]

I've bought aftermarket barrels and they fitted fine from the start. I've also fitted a couple of barrels that were advertised as you mentioned. The difference between "doesn't work at all" and "works fine" is extremely slight. It's amazing just how little has to be stoned or removed from a lug or barrel hood to make a proper fit. By the same measure, it's just as slight going from correct fit to "oops - too much".

The challenge, if the part doesn't fit, is knowing what to cut and what to leave alone.

In my limited experience, if the part fits without binding and functions, but is a bit tight - it will work. Might require a few rounds to break in. If it's not going to work, it generally won't fit and won't function. There are exceptions. For example, a 1911 barrel with too long a link may function properly while at the same time beating the heck out of the locking cuts of the slide.

It should be remembered that if upgrading the pistol is the goal a part may fit and the gun function because of a too loose fit. I'd prefer a barrel that requires fitting to a barrel bushing than one that is undersized and "drops in". Most semi pistols these days don't have a barrel bushing, but the theory remains the same if parts are cut undersized to ensure easy drop in.