Collet barrel bushings

[dsk]

L- standard solid bushing, R- Colt collet bushing

I often see threads started asking about so-called "collet" barrel bushings, usually in reference to Colt pistols. The collet bushing was introduced by Colt in 1970, and is easily identified by being made of spring steel with four "fingers" at the rear. The last batch of standard commercial Governments in 1970 incorporated the new barrel bushing and matching barrel (which has a slightly belled muzzle) as a test run. These pistols (approx. 1500 made) had conventional post-war commercial markings, but had a special "BB" marking underneath the serial number. Later that year the new system it was formally introduced as the "Accurizor barrel and bushing" with the new Mark IV/Series 70 models later that same year, which included all 5" barreled pistols (Government Model and Gold Cup). The shorter 4.25" Commander models continued to use solid bushings. How they worked was that the spring "fingers" of the bushing were pushed out by the belled end of the barrel during lockup, and wedged between the barrel and inside surface of the slide to tighten the fit and improve accuracy. For the most part it worked great, as the accuracy of a typical box-stock Series 70 usually exceeded that of earlier commercial pistols with standard bushings. It was basically a means of improving out-of-the-box accuracy on production pistols without going through the expense of hard-fitting match bushings like those used on custom accurized pistols.

The collet bushings remained in use past the the introduction of the Series 80 models in 1983, but were eventually phased out around 1988 or so when the solid bushings were reinstated. The reason for them being discontinued was due to a rare but potentially serious issue with the bushings. In the manufacture of firearms the matter of maintaining design tolerances is always an issue, and in the case of the Series 70 bushing system it was critical. If the slide inside diameter (ID) was machined too large the fingers of the bushing couldn't wedge between the slide and barrel snugly, and accuracy would be lackluster. If the slide ID was machined too small then the fingers would have insufficient room to expand during lockup, causing them to flex and buckle at a point just ahead of the pads that contacted the belled end of the barrel. Eventually one of the fingers could break off due to being overstressed, with the broken piece floating around inside the weapon. Since the pistol would continue to operate normally it would likely go unnoticed by the user, at least until it jammed somewhere inside the pistol, possibly locking up the pistol while it was still loaded. Gunsmiths weren't usually too happy to receive a still-loaded Colt that was jammed up in this fashion, especially given the fact that freeing it up usually involved putting the pistol in a vice, taking a rawhide mallet and banging the slide back and forth until things came loose. It wasn't healthy for the gun, and it wasn't healthy for the gunsmith either if there was still a round in the chamber.

There are many owners who say they've already put thousands of rounds down the tube without experiencing a broken bushing. Odds are they won't, because the vast majority of pistols were manufactured within proper specs, and by now it's probably evident whether or not there's an issue with tolerances in their particular weapon. It's just that one in a thousand that may end up breaking. But that is why I usually tell people to replace the collet bushing with a solid one anyway just to be on the safe side. Your pistol will probably never have a problem, but the fact is you really never know when it'll fail. It may a long time before the fingers finally succumb to fatigue and break off. Maybe after 5,000 rounds, maybe after 50,000. I've kept the one in mine simply because it's more a safe queen than a shooter, but if it were being used for competition or defense I'd replace the bushing with a standard solid unit.

One frequently-heard comment is that you should never pull the collet bushing off the barrel, otherwise you may stres the fingers further and cause them to break. This is not true, as you can be rest assured there are greater stresses imparted on the bushing during actual firing than if you simply popped it off the end of your barrel! However it is true that when disassembling a Series 70 you should retract the slide at least 1/4" when trying to rotate the bushing, as you'll be releasing the bushing from engagement with the slide/barrel and thus making it a whole lot easier to turn.

And yes, to answer another frequently-asked question, a standard non-oversize solid bushing will work on an early Series 70 or 80 pistol. The belled muzzle on a Series 70 barrel is still the same outside diameter as a conventional "straight" barrel, so a factory Colt solid bushing should drop in without fitting. Aftermarket oversized units (Wilson, Brown, etc.) will of course require gunsmith fitting to the slide and barrel as with any other type of 1911 pistol.

Once again, the only factory pistols you're likely to see them in are Colt's Government Models and Gold Cups made from 1970 through 1988. Commander and Officers ACP models never used them nor did any of the so-called "clone" makers, although I am aware of some aftermarket companies (such as Bar-Sto) who offered collet bushings for Commander-sized pistols for a short time during the 1970's.