Patterning For Perfection
January 04, 2011
Patterning a shotgun isn't only for turkey hunters and hard-core clay bird busters. Anyone who pulls the trigger on a scattergun will benefit from knowing where it shoots and how it performs.
Even as I write this, I have to admit there are shotguns in my gun safe that I haven't patterned, and that I use for shooting and hunting. I shoot reasonably well with them and usually manage to break a few clays or bring home a bird or two from the field. We're fortunate that factory-made guns are generic enough in their dimensions that when combined with a pattern of decent size and density allow us to make hits, even if they might be at the edge of a pattern. But every time I miss a rooster or knock just a chip from a clay bird on a shot that "felt" right, I have to wonder if it was me, or if the load I was using didn't perform the way I thought it would. When I get around to patterning those shotguns, I'll know that answer.Why Pattern?
Patterning is done at 40 yards unless you're shooting .410-bore shotguns or "skeet" chokes. In those instances, pattern at 25 yards.
There are two fundamental reasons for patterning a shotgun. Foremost is to find where the shotgun puts its pattern relative to where you point it. Second, patterning will show you how a certain shotshell patterns with a given choke or choke tube.
With shotguns, your eye is the rear sight so every time you mount the gun, wherever you plant your face on the stock determines the setting of your "rear sight." If you mount your gun consistently, your shots will be consistent. Fuller faces tend to position the eye more to the left causing shotguns to pattern to the left, while long faces can cause a gun to shoot high. Naturally, the reverse is true. Custom-fitted shotguns are made to the physical dimensions of a shooter so that the gun patterns where the shooter wants it and many new shotguns come with shims to allow the user to make some adjustments. Even shotguns with fixed buttstocks are capable of being easily adjusted by many shooters or by a competent gunsmith. As few as five shots on patterning paper can show where the gun shoots, and which way to adjust it for optimum pattern placement and fewer misses.
When shooting a shotgun, your eye is the rear sight. How the shotgun fits determines the "setting" of your rear sight. Patterning will show if you need to adjust your stock so the patterns hit where you want them.
How a shotgun shoot refers to how tight it patterns. Chokes and choke tubes come marked with constrictions to indicate how tight the choke should pattern. Full, modified and improved cylinder are the most common chokes, and all shotgunners should have an understanding that full choke patterns tighter than modified and modified patterns tighter than improved cylinder. There are two ways choke is usually determined. The first is to physically measure the inside constriction of the choke and compare it to a standardized table. The second is to fire through the choke and determine the percentage of hits in a 30-inch circle at 40 yards (25 yards for "skeet" chokes or .410-bore shotguns).For the most part, the choke marking on factory guns reflects the physical measurement of the choke, and does not necessarily reflect the actual pattern percentage. That percentage can be determined only by firing on patterning paper. Patterning by percentage may show that the "choke" varies from one brand of shell to another and from one shot size to another.
It doesn't take much to pattern a shotgun. You'll need large sheets of paper, something on which to hang them 40 yards away that has a safe backstop, eye and ear protection, possibly a 15-inch piece of string, magic marker, your gun and ammunition and a calculator.
Use a sheet of paper that is at least 48 inches on each side so that it is large enough to get a good measurement from the pattern. Many print shops will have "butt ends" that cost little or nothing.
When it comes to the paper, you'll want a piece that is at least 48 inches on each side so that it is large enough to get a good measurement from the pattern. Some authorities have recommended newspaper, but I think with all the print it's too "busy" making it hard to see small pellet holes. Even small towns usually have their newspaper printed nearby, and many of those printers will part with the "butt ends" of newsprint rolls for little or nothing. Those butt ends are simply the unused ends of newspaper rolls left over after a print run and make good patterning paper. As appealing as it seems to get a possibly free roll of patterning paper from your printer, preprinted ones will save you a lot of time when it comes to actually analyzing your shots.
Hanging such a large sheet of paper can be problematic, especially at a public range, but more and more ranges are installing patterning ranges so the problem is getting better. Personally, I've found a three-strand barbed wire fence and a handful of binder clips work great, but if you use a fence, make sure it's okay with the person who owns the fence, and that it has a safe backstop. My experience is that small lead shot will not damage barbed wire, though I can see where large lead shot, steel or Hevi shot might. For those types of shot, I use two 5-foot long pieces of rebar stuck in the ground four feet apart and clip the patterning paper to it with binder clips.
Eye and ear protection is not as straightforward as it sounds. If you shoot competitively, wear the same safety equipment you use on the firing line. For that matter, wear the same shooting vest and type of clothes you wear on the line. If you are patterning a shotgun for hunting, use the same eye and ear protection you use hunting, or use earplugs if you don't wear hearing protection afield. Try and wear the same thickness clothing you would use hunting, too. The reason is that large muffs can cause you to mount the gun differently, as can different thickness clothing, or shooting vests with slick shoulder pads.
If you're using plain paper for patterning, use the marker to make a reference point in the center of the paper. The marker is also useful later when counting pellet holes to mark the ones you've counted. When attached to the 15-inch piece of string, the marker used as a compass makes drawing a 30-inch circle around the pattern easier.
Pattern all the different type of loads you shoot. Don't be surprised if your gun shoots different "chokes" by percentage with the same choke tube. Guns are like people in that they have specific tastes when it comes to what you feed them.
Ammunition should be the type you intend to use afield or on the shooting range, and you'd be ahead of yourself to have a few different brands and shot sizes to compare. Different ammunition manufacturers use different types of wads, hulls and lead alloy blends for shot — all of which can make a difference in how you gun patterns a particular load. For that matter, different lines of shells from the same manufacturer may pattern differently enough to warrant comparison.
Mark a reference point in the center of the patterning paper, then step back 40 yards for all gauges and chokes except .410 bore or "skeet" chokes. Those are patterned at 25 yards.
How to Pattern
If you're patterning to see where your shotgun shoots, hang your paper and mark a reference point at the center of it if you're not using pre-printed patterning paper. Step back 40 yards, load your shotgun, and hold it at rest as you would when hunting or at the trap or skeet range. Raise and fire one shot at the reference mark you made, just as you would when calling for the bird, or when one flushes. With double-barrel shotguns, whether over-under or side-by-side, use a separate sheet of paper for each barrel. Repeat this about five times at the same piece of patterning paper, being sure to start with the gun down for each shot. After you've fired five or more shots, go downrange, draw a circle around the patterns, and compare where your shotgun patterned to your reference mark. You should be able to distinguish the outer edge of the five patterns to see if they're centered on the reference mark or not.
Personally, I like for my shotguns to pattern a little high so I can keep a rising bird in sight over the rib of my gun in case it changes direction or speed and I have to adjust my swing accordingly. If your gun needs adjustment, follow the manufacturer's instructions if it came with stock shims, or take it and your patterning paper to a gunsmith. Be sure to mark the top of your patterning paper so you don't adjust the wrong way and make a bad situation worse.
Circle the shot holes with a marker and compare the centering of the pattern to the aiming point. If it's off, either adjust the stock yourself, or mark the top of the paper and take it and your shotgun to a gunsmith.
When it comes to how your gun patterns, you'll sometimes find that the constriction indicated on a choke is not necessarily how it patterns according to pellet percentage. You'll also find that a certain choke may fire a modified pattern for example with one specific load, but fire a full or improved cylinder pattern with a different load. That's important information, especially if you're shooting game that is typically up close and personal such as woodcock or quail, or when taking passing shots at high-flying waterfowl.You'll get better patterning percentage results using a shotgun that is adjusted to center its patterns on the paper because you'll get more shot pellets on paper for a more valid pellet count. For that reason, I highly recommend first patterning for where your gun shoots and making any necessary adjustments before patterning for percentage.
To get choke value according to the pattern percentage, hang a sheet of patterning paper just like you did before, step back 40 yards, and fire one well aimed shot at the center of the paper. Change the paper, and fire another single shot. Repeat this until you have fired at least five shots — one shot on each paper. Next, you'll need to know how many pellet holes are in a 30-inch circle on the patterning paper. Pre-printed patterning papers typically have a primary 30-inch circle around a central mark and four offset circles so you can select the one that has the most pellet holes in it. If you're using plain paper, hold one end of your 15-inch string down in the center of the pattern, and use the other end with the marker to draw the circle in the same way you would make a circle with a compass.
Counting shot pellet holes is a tedious and boring job. Keep from losing count by sectioning the pattern and writing the subtotal of hits as you count.
Once you have your pellet holes circled, you will need to count them. I've probably counted more than a million pellet holes in the past ten years, and I've found the best way to do it is to divide the circle into sections, and record the subtotal in the sections as you progress. Mark each hole as you count so you don't double count. Determine the average number of pellet holes in the 30-inch circle by totaling the number of holes in all of the 30-inch circles, and dividing by the number of patterns. Once you have the average number of hits in a 30-inch circle, divide that number by the average number of pellets in your shotshell according to the box or factory tables to get the percentage. Compare your percentage to the accompanying table to see how a particular choke actually patterns that load. If it doesn't perform the way you want, change chokes or change ammunition and pattern again.
When you know where and how your shotguns shoot, you'll have fewer excuses for missing. But then, you'll also be a better shot, and will need fewer excuses.
|Choke|| Inches Constriction ||Percentage|
| Full|| 0.036 ||60-70%|
|Modified|| 0.011 ||55-60%|
|Improved Cylinder|| 0.007 ||45-55%|