All Choked Up

All Choked Up
Using choke reamers, the author opened the chokes on his client’s gun so that they were shooting the desired patterns with the loads being used.
By Delbert Whitman Jr.

On a glum and cloudy day this past spring, a client and good friend of mine paid an unannounced visit to my shop. In his hand was a very nice side-by-side boxlock game gun. The look on his was face was as glum and unpleasant as the weather. A small but quite reputable London maker circa 1908 had made the gun he was carrying. It was a 12-bore and had 28" tubes and a straight grip. The action was dainty for a 12-bore, and thus the gun was light and felt dynamic in the hands. The gun had the sharp, sleek look that many British guns from that era do. I had seen the gun shortly after he had acquired it, and upon doing a cursory inspection knew it to be in incredibly good condition.

I inquired about his foul mood. He said that he could not hit the broad side of a barn with the gun, even if he were standing inside. He was at a complete loss as to why. I was rather perplexed as well. From the prior inspection, I knew that the gun’s fit was nearly ideal for him. The chokes were set at an amicable Improved Cylinder & Light Modified (i.e, .009" & .015" constriction). A barrel-regulation issue would have been a total anomaly for a gun of that quality. I also knew my friend to be a remarkably good shot. He consistently broke mid- to high 40s on a 50-bird clays course, and very few birds flew away from him in the field.

So out of deference to my friend’s obvious dismay with the new gun, I put away what I had been working on and endeavored to figure out what was going on. The first thing I did was a thorough inspection of the barrels. The bores turned out to be slightly overbored to .735". This was well within proof and not uncommon for a gun of that age. The chokes and choke forcing cones were in perfect condition. The only other thing to do was take the gun to the patterning plate and see how my friend was shooting it.

All Choked Up

At my British-style, 16-yard patterning plate, the issue became immediately evident. Using high-quality, low-pressure ammunition, he fired one shot from each barrel at two different 6" aiming points on the plate. Both of the shots were dead center on the targets, but both patterns were scarcely larger than my fist. Having measured the chokes, this took us both by surprise. We then set up my standard 40-yard patterning board and conducted formal pellet-density pattern tests. We discovered that the right barrel was shooting a light Full pattern and the left a true Full pattern. At reasonable shooting distances, the pattern diameters were roughly half of what the choke constrictions seemingly dictated they should be.

This is an issue I see more and more these days, and it understandably can have a dramatic effect on one’s shooting performance. If you head to the field believing you are shooting Improved Cylinder & Light Modified and in reality are shooting Full & Full, some obvious disappointment will ensue.

This problem is created by the confluence of two separate yet interrelated issues. One is the antiquated numeric system we use to designate choke. The other is the superior quality and technically advanced shotshells we have these days.

I wonder how many sportsmen are dealing with this and don’t even realize it.

I’m going to use some numbers in my explanation. They are based on 12-bore data, but keep in mind that choke-constriction designations are proportional to bore size, so the numbers for a 12-bore will be proportionally less for smaller gauges.

The term “choke” is colloquially used to describe the diameter of a pattern at a given distance. But from a technical standpoint it’s defined as the percentage of the initial payload of pellets that hits inside a 30" circle at 40 yards. If 70 percent of the pellets hit in the 30" circle, it is considered a Full pattern; if 60 percent hit, it is a Modified pattern; if 55 percent hit, it is Improved Cylinder; and if 40 percent hit, it is Cylinder.

Somewhere around the turn of the century in literature and advertisements we started to see the common choke-name designations we still see today: Cylinder, Improved Cylinder, Modified, Full and their various permutations. These designations had corresponding numeric constriction amounts: Cylinder, .000"; Improved Cylinder, .009"; Modified, .020"; and Full, .040".

The issue here is that when the choke designations were associated with their constriction amounts, the ammunition that was being used was inferior to what we have today. Wads consisted of various layers of paper and felt fiber. There were no barriers between the shot columns and the barrel interiors. The felt wads did not form good gas seals, so there was gas blow-by, necessitating the use of larger amounts of powder. Shot was typically pure lead, which is soft and prone to deformation, and it often was not round to begin with. The result of all this was that a lot of shot came out of barrels badly deformed and thus did not fly true, resulting in larger and inconsistent patterns.

I believe that many of us take for granted the quality and technical advances of the shotshells we have today. Perfectly round shot is alloyed with antimony and other elements for increased hardness, and in some cases it is plated with copper or nickel. The plastic wads surround and cushion the shot column and form a perfect gas seal. Progressive-burning powders reduce pressure. The result of all this is that the vast majority of shot comes out of the barrel as round, straight-flying pellets, resulting in denser and tighter patterns.

So in effect the modern high-quality ammunition we use today can cause a mistranslation in how we perceive the size of the patterns our guns shoot. If a gun has .009" of constriction, we still consider it to be Improved Cylinder; but in reality, with today’s superior ammo, it could be patterning significantly tighter. I wonder how many sportsmen are dealing with this and don’t even realize it. The only way to find out is to undertake the tedious but potentially hugely beneficial task of pattern-testing guns with the different shells that are being used.

To remedy my client’s problem, I got to work with my bore-piloted, expandable choke reamers and honing equipment. I reamed out and opened the constrictions in .005" increments and did formal 40-yard pattern analyses after each reduction. At the end of this long process, the gun was patterning the desired Improved Cylinder & Light Modified. In effect, I had fine-tuned the amount of choke constriction to shoot exactly the pattern size my client desired with the modern ammunition he was using. As a result of this choke work, he is now shooting his fine new gun at his usual high level of proficiency.

Delbert Whitman Jr. lives near Traverse City, Michigan, with his wife and daughter. He is a professional gunsmith specializing in repair, restoration, stockmaking and engraving. He also is a passionate upland-bird hunter and English cocker spaniel owner.

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