Patterning Vs Point Of Impact


Dear Technoid,

I have recently acquired an AYA #2 12 gauge (my first SxS) choked cylinder and skeet2. I was fitted for this gun by a well known gun fitter and the gun seems to fit me quite well. I will use this gun mainly for pheasants which I hunt with my German shorthair.

One thing I am unsure of is the proper way to pattern it. When I pattern my guns I usually shoot at a target that is at a measured 40 yards away from the muzzle of the gun. I aim my O/U “rifle style” when patterning it which seems to work quite well. If I aim the SxS “rifle style” (with the bottom of the bead resting on the horizontal line of the breech, and the bead covering the dot on the patterning board) it will print most, if not all of the effective pattern below the dot on the patterning board. Is this normal behavior for a SxS, is muzzle flip causing this? Or is my gun shooting low.

When shooting clays with it I do well (which could be considered pitiful by most folks). I assume this is because there is a fair amount of the barrels visible when I shoot clays which would cause it to shoot higher.

Here are my questions. Is my gun shooting low? And what is the proper way to pattern a SxS?

Clark

Dear Clark,

There are two distinct steps to evaluating the performance of a shotgun. The first is point of impact and the second is pattern performance.

Point of Impact involves WHERE the gun shoots. Pattern Performance involves HOW it shoots. Unless the former is correct, the latter is irrelevant.

Your gun fitting session should have involved assessing point of impact. Each “professional” gun fitter has his own techniques, but all the good ones that I know of use dynamic testing on a pattern plate. I am VERY suspicious of the “gun shop” gun fitters who merely look at the position of the eye’s iris over the rib. Shop fitting is convenient for all concerned, but nothing can replace shooting the darn thing.

You comment that your SxS shoots lower than your O/U when “aimed” at a mark, yet you shoot the SxS well at clays. It would appear that you are not cheeking the SxS quite as hard when you shoot at moving objects. Nothing wrong with that if that is the way that you shoot.

The only time I “rifle shoot” a shotgun in testing is to check barrel convergence to see if both barrels shoot to the same point of aim. All point of impact testing is done when moving the barrels. It really should be a dynamic, not a static, test. The best method is to use a very large pattern plate. 6’x6′ is good. Many plates have five aiming points on them, somewhat like the 5s on a pair of dice. This saves repainting after each shot.

Starting with a low gun, raise and quickly fire at the center point. Then, again starting with a low gun, but beginning off to the side, raise and swing through to another point and fire. Then do it from the other side, then top down and bottom up. Repaint the plate and repeat as necessary. Pretty soon you will get a good feel as to where you gun shoots when it is moving as it would in a hunting situation. THEN you can make the appropriate stock adjustments.

If no pattern plate is available, you can do a fair job on a skeet field if you are a consistent shooter and if you instructor knows how to read breaks. The plate AND the skeet field are the best approach and that is what we use around here.

One of the hardest things about fitting a gun is to deal with a newer or occasional shooter whose shooting style is still in flux. You have to fit for what his correct style WILL be, not what it is at the moment. This is more art than science.

SxS guns are generally stocked a bit higher than O/Us. SxS guns just shoot lower for most people. This may be due to barrel flip of the difference in visual perception caused by barrel configuration. All my guns have the same point of impact, but my SxS is stocked MUCH higher than my O/Us, but it shoots to the same place.

If you are curious as to whether your SxS shoots low, why not just layer some tape onto the top of the stock and shoot some clays with it that way. See if you shoot better. Make sure not to have the tape come over the comb onto the inside of the stock so that it gives additional cast-on, unless that is what you want. If your gun does shoot better with tape on it, experiment to get just the right amount and then take it (with the tape ON it) to the stock bender and get it rebent. If you shoot too high with the tape, then you know that you are right as it is.

As to patterning- counting pellets- the standard approach is to get the largest piece of paper you can find (36″ is minimum and barely satisfactory), mark a central aiming point. MEASURE 40 yards from the paper to the muzzle of the gun. I said MEASURE. Aim at the mark and fire. Write the shell and choke on the paper and shoot all the combinations that you want to test. You might get away with only three tests of each combination, but five would be better. 36″ wide Red Resin Flooring Paper is dirt cheap at the local lumber yard and comes in giant rolls.

Take all your papers home. Lay the first one out on the table top back side up. It is easier to see the shot holes by looking at the little exit “volcanoes” than at the “innies” on the front. Now eyeball the center of the pattern and mark it. Pay no attention to the central aiming point that you used on the front of the target. Draw a 30″ circle around the center point that you have just eyeballed. Using a yard stick with two holes drilled in it makes a handy compass. Now count your pellets. I dab each hold with a Magic Marker as I go to keep count. Watch out for your dining room table because the Magic Marker spots go through the paper.

That’s about it. You can learn a lot about where your two barrels converge by comparing the aiming points and the actual pattern centers of the two barrels. Don’t be at all surprised if they aren’t exactly the same, but they shouldn’t be too far off.

One final point- more old and faithful game-getting guns are sold after detailed patterning and point of impact testing than at any other time. If your gun really works well for you, sometimes it is best not to know the fine details. Barrels that shoot 5″ apart will drive some people crazy once they find out, even though they have been using that gun to kill birds every year.

Best regards,

Bruce Buck
Shotgun Report’s Technoid
(Often in error, never in doubt.)

This entry was posted in Shotgun related. Bookmark the permalink.

Leave a Comment

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.