October 09, 2013
In past articles, I have focused on fitting the rear end of the barrel to the slide and slide stop for maximum accuracy. Today, we will consider the barrel bushing and its fit to the slide and barrel. Ideally, you want a bushing with an outside diameter that is a press fit in the slide, and an inside diameter that is as close to the barrel outside diameter as possible while still allowing reliable function of the pistol.
Most factory bushings are of the "drop-in" variety, meaning no hand fitting is involved during assembly. When accurizing 1911s, standard practice has been to hand fit a bushing with oversized outside diameter and undersized inside diameter.
The bore was cut with an adjustable reamer to just fit on the barrel and the outside dimension was reduced on a lathe or with sandpaper while turning in a fixture. Time consuming, to say the least. What if you could order custom bushings that are close to dimensionally correct for your slide and barrel with only minimal fitting?
Evolution Gun Works of Quakertown, Pa., is offering just such a product. They sell bushings with various outside diameters that are custom bored to your barrel dimension. Not only is the bore matched to your barrel's outside diameter, but it is "angle bored" to match the lock-up angle of the barrel and the flange is thicker than a standard bushing to provide more support for the muzzle.
You must supply EGW with accurate dimensions to ensure a good fit. The barrel can be measured with a caliper or better yet a micrometer. Determining the inside diameter of the slide may be tricky. I use a hole micrometer to get an accurate reading.
In this case I'm fitting a Kart barrel to a Springfield Armory 1911. Karts are usually .581 inches at the muzzle, but that dimension is verified to make sure. The slide inside diameter mics out to .702 inches, but I'm going to order the bushing in a .703-inch outside diamater and polish it to achieve a press fit. The custom bushing made to my specs cost only $27.50 plus shipping. A bargain.
When polishing the bushing outside diameter to fit the slide, I used the Brownells Bushing Fitting Mandrel turned in the lathe with excellent results. A light polish with strips of 220- and 320 grit-paper was all that was needed.
With a flange that is thicker than a standard bushing the factory spring plug looks incorrect. EGW sells a special "long nose" spring plug ($15) to match the bushing. The bushing in the gallery is the "carry bevel" version with chamfered edges, which looks quite nice on most pistols. The EGW custom bushings provide an attractive alternative to the standard NM bushing for gunsmiths and advanced hobbyists.
An EGW custom angle bored bushing and matching long nose spring plug. The long nose lets the spring plug line up evenly with the front of the bushing.
Measuring the Barrel
Taking an accurate measurement of the barrel outside diameter is critical when ordering a custom bored bushing. A caliper is good, a micrometer is even better.
Measuring the Slide Bore
A hole micrometer is used to measure the bore of the slide. This is a tool a lot of home gunsmiths won't have at hand and will have to substitute.
Brownells Bushing Mandrel
The Brownells bushing mandrel is turned on the lathe and the bushing outside diameter is polished with strips of sandpaper to final fit it to the slide.
The Finished Product
The front surface of the spring plug can be checkered if you want a traditional look. The long nose makes it look right.