1911 Pistol Modifications - Top End Fit
by Dennis L. Schrieber, Pistolsmith
Whats the one thing that we all took for in a firearm? The most common answers are probably accuracy and reliability. The top end of the pistol is what determines most of this. Accuracy and reliability come from repeatability. The slide and barrel must return to the same relationship too the frame each and every time. To that end, at least three areas come immediately to mind: the slide to frame fit, the barrel fit and the fit of the barrel bushing. >
The frame to slide fit is where we should always start. This is the foundation of the whole top end. It really doesnt matter how good we fit a barrel or bushing if this foundation is unstable. As with all foundations it can also be a major problem area. One factor that must be considered before a slide is fit is the ultimate use of the pistol. A pistol designed for bullseye will be too tight for ISPC and etc. I like to grade pistols in seven categories, ranging from military (rattle - battle guns) to the precision bullseye grade. >
A properly built grade 1 bullseye gun will hold a group of 1 ½ at 50 yards. That is about as good as a match barrel will do when shot from a barrel fixture. The problem here is that a gun that tight will only fire a hundred rounds or so without cleaning. This is fine for shooting a national match course but, would never do for most other disciplines. The traditional way to achieve the proper fit is to peen the rails and squeeze the slide. Then file and lap the mating surfaces to the desired fit. The alternative is the installation of Accurails. Accurails can only be installed by a shop licensed by the manufacture to do so. The cost of either method is about the same and each has its place. The rails are an advantage with we are looking at a piece that is very loose or with minimum size rails (0.109). Rails are the only choice on an all stainless gun. Either method should last 60 to 70 thousand rounds before needing additional work. >
Barrel fit is equally as important but, must be done after the slide and frame are mated. The barrel must lock up into the slide solidly each time for both accuracy and safety. By forming a series of triangles between the points of fit, we can assure that this occurs consistently. The barrel should lock on the upper locking lug at two and ten oclock, fully on the two lower lugs, at the end of the barrel hood and of course at the barrel bushing. These points will form eight triangles and as we know, a triangle cannot be deformed without changing the length of one of its sides. To achieve this degree of precision we must start with an over size barrel. It would be a one in a million shot to get a true fit with a drop-in part. >
Please, keep this all in context, what I am talking about here are target guns. Those intended for those who demand the highest in accuracy and performance. But, there are lessons here for all of us. Not until we understand how all the components enter-act to form a system, can we made good decisions about our own equipment. So, good shooting, keep it fun and safe, and remember to visit your favorite pistolsmith. All comments should be directed to Dennis L. Schrieber, Burnt Mill Smithing, www.burntmill.com or firstname.lastname@example.org.