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Patterning a Trap shotgun

50K views 32 replies 23 participants last post by  gyrine 
#1 ·
What are the suggested methods for a patterning a Trap shotgun?
Some suggest use 13 yards, others 25 yards and so on.
Should the gun be shoulder mounted or bench rested or both?
Should you check it using different loads?
Preferred chokes used, any recommendations?
THank you.
I. Hartman
 
#4 ·
Test at 13 yards to make sure the gun shoots straight. Then set the gun up so it shoots a little high. You need a built in vertical lead for trap shooting, because you are shooting at a rising target.

Now it's time to test it on some clay targets and fine tune your adjustments. This is best done on station #3 on the trap field with the machine set to throw straight away targets. HMB
 
#6 ·
You must learn the difference between "patterning" which is counting pellets in a certain size circle at a given distance ( 25, 30, 35, 40, 45, or 50 ) yards. and POI ( point of impact ) at whatever distance.

Some here seem to like 13 yards for POI, although I have never understood why. But some type of POI checking is always benifical to be sure the gun's barrel (or barrel's) shoot straight. I would agree more with pheasantmaster. He seems to be on target with his accessments and explanation.

Tom Strunk
 
#7 ·
I pattern several different ways.

1. 5 shots at 35yds to check POI. From the bench.

2. 5 shots @ 35 free standing to reveal consistency/flinching. Amazing how loose these shots are compared to the bench. Also amazing how sometimes you can hardly tell the difference. Depends on the shooter.

3. 1 shot benched to count pellets for pattern density and to check several different types of load/speed combinations.
Todd
 
#9 ·
I.Hartman here is some advice I gave to Bob last year, plus some addition thoughts. I'm going to cover all the basics, step-by-step, assuming you don't really know anything about your gun yet.

The first thing you have to determine is where your gun shoots. When you are satisfied the gun shoots straight, you'll want to determine where you shoot it.

Set up on a bench with a target between 13 and 20 yards in front of you. If you have interchangeable choke tubes, you'll first have to determine whether they all shoot to the same place. Pick a barrel and put a choke tube in it. Sight the shotgun just like it was a rifle and fire at your POA. Do this at least 5 times, or enough so that you can say with authority this choke prints 1" high and 1/2" right of POA. Now do the same for every other choke. Make sure to use the same barrel for all of these tests. At the end of your choke testing you will know which chokes shoot to the same POI and which don't. Mark or discard the ones that don't.


If your new gun is an O/U, put your two tightest good chokes in and repeat the test. That will tell you if both barrels shoot to the same POI. If a combo, all three barrels should shoot to the same POI with the same sight picture and setup.


Once you know your hardware is good, it's time to see where you shoot your gun. I like to work on one variable at a time. Any distance from the muzzle to target between 13 yards and 20 yards will work. I prefer 15 yards most of the time for reasons I'll not get into here. I use 40" wide paper and draw three vertical lines on it about 12" apart. Then I mount the gun while standing just as I do on the line, and fire while tracking a line. I find I'm much better if the gun is moving, so I just trace the line with my bead and fire whenever. I only care about right and left here. If I'm consistently dead on the line, I'm done. If not, I move the comb right or left until I am.

Next I repeat the process using horizontal lines. Here I am trying to set my POI to the proper height. I know what my POI needs to be because I have already established it through experience. If you have not, then set you gun up so it shoots about 2" high at 13 or 15 yards, then go and do as hmb suggests. Lock the trap to throw straights and shoot a bunch. If you are smoking birds and you like your sight picture, move to Station 1 or 5 and repeat. If you are not happy, adjust your comb to raise or lower your POI until you are. Then move to 1 and 5 and adjust again if necessary. The idea is to find what Phil Kiner calls your natural POI. I'll also add the following: you are unlikely to get it perfect in one session. You'll be close, but next week you may be just a little off. That's fine. Make a minor adjustment and go with the flow. Sooner or later your subconscious will tell you "this is right".

Now go back to the target board and do the horizontal line bit again. You are shooting to determine your actual POI for reference. Just for the sake of argument, let's say you find the gun shoots 4" high at 13 yards. Write it down. That way you have a reference you can always return to if you have been experimenting, or you change guns, etc. The core idea here is you made the gun "shoot where you look" by actually firing at real clay targets, and only then determined your actual POI for the record. It is sheer lunacy to arbitrarily say I will set the gun up for x" high or x/y percentage, and then go shoot.

Now for patterning. Patterning takes a lot of time and effort if you want good, believable results. If you have a "good" barrel, almost anything you feed it will work well. I'm well past thinking another 10 pellets in the inner 20" circle is going to get me another bird. Personally, I'm much more interested in uniformity than I am in actual PE (Pattern Efficiency). If you have a "bad" or finicky barrel or choke, you'll be testing many more loads.

Here's the deal. Trap is shot with tight chokes. Tight choke forgive a multitude of sins, patternwise. So I'll suggest you take your favorite singles load and shoot it for singles. Now that you have your gun set up properly, you'll know if the load is performing. Do the same with caps. Good loads are the ones that work. You'll quickly find a few that you really like.

If you are still interested in patterning, or simply want to find out which of three pet loads works best in your gun, go at it. I do all my "official" patterning at a measured 40 yards. I do that because I shoot tight chokes and you simply cannot tell anything of real value at 32 or 34 or 35 yards unless you are shooting a modified or looser choke. I also do all of my "serious" patterning in the winter. There are two reasons for this. First, as Bob Brister notes in his book, patterns from a full choke spread in a trumpet shaped pattern. They start out tight, stay together for quite a while, then suddenly begin to flair out much more quickly, just as a trumpet does near the front. The tighter the choke, the farther away this happens. Second, air is denser in the winter and causes patterns to disburse more quickly. I want to magnify differences, and patterning at 40 yards on a cold winter day is the way to do that.

Remember, right now I'm comparing two loads that I already know work well. I'm not interested in determining whether I got 68% or 70.4% PE. I'm interested in comparing the performance of two loads, one against the other. The one that gives me the most even patterns wins. I shoot a minimum of ten patterns each, often more, before I form any kind of conclusion. I shoot from a bench, carefully, and use Shotgun Insight to analyze the patterns. It tells me what I need to know.

BTW, if you find a load that gives you 70% PE @ 40 yards when the temp is 30 degrees, that load will give you 82+% PE in the warm summer months. That's why I pattern in winter. Small differences are easier to pick out.
 
#14 ·
My method of patterning a trap shotgun:
1. Adjust the comb so that you see the correct sight picture - figure eight.
2. Shoot a round of 16 yd targets; targets will be smashed.
3. If #2 leaves targets not properly reduced to dust, make further comb adjustment after noteing the direction of the chips (move comb in opposite direction of chips).
4. That is all it takes; I have adjusted several shotguns using this method and have yet to use #3.
 
#16 ·
dzneff- Your comments were directed toward setting up a shotgun to shoot where you are looking. This is not patterning. You mentioned "patterning a shotgun" but actually, we pattern a load, not a shotgun.

A typical patterning question would involve the difference, if any, between a factory AA wad and a Claybuster clone of the wad. To answer such a question, analysis of at least 20 patterns will be required. It is a lot of work.

I must also question your comment indicating a figure eight is the correct sight picture. It is my contention that sight picture (relation of mid bead to front sight) is not important. What is important is getting the gun to shoot where you are looking.

Pat Ireland
 
#17 ·
Patterning and testing loads is an important part of the game to a lot of people and provides them much enjoyment. Others, like me, have only a passing interest in such things. However, it is important to establish where your gun shoots and where you shoot your gun so that you have the confidence of that knowledge when you go to the line.

Without getting into a discussion of the geometry of POA, POI, sight lines and bore lines, my Reader's Digest version is this:

1. Trap targets rise and shot strings fall. As such I see no reason to have any pellets below the POI at the target breaking distance.

2. Most FCs will produce about a 22 -24 inch sure kill pattern at 35-40 yards.

3. To get this kill pattern above the POI at 40 yards means you have to get the bottom of the pattern about 12 inchs above the POA. Consequently, a POI of about 4 inchs at 13 yards will accomplish this.

4. Shoot the 13 yard POI shots from some type of rest. It is a shotgun so if a bench rest is not available, so what? Just use something to steady your aim.

5. Put a big mark on a patterning board/paper at 40 yards. I like to raise the gun up to the mark and fire when I think I have the sight picture I am used to seeing on a straight bird from 3. If the 6 o'clock of my pattern is right above the mark, I'm done.
 
#18 ·
I hate to be different but I relate patterning a trapgun to the kiss of death. It's just me, but after 35 years of shooting BT-99's, BT-100's, & a 90T, if the gun shoots where I look and the target is reduced to a puff of smoke, it's good enough for me. Since a shotgun shoots a pattern of 3 dimensions, I don't believe me pattering my guns would do anything more than make me doubt the load or gun. I see the guys constantly patterning their shotguns, then go back and make a change to the choke and/or stock, and then the next month do it again. This usually is after a few missed targets and after watching them year after year it's comical; they have not figured out that it is the fault of the operator... Their stock comb goes up & down like a bride's nightgown sort of speak. That's just my opinion. Darrell
 
#19 ·
Darrell- I disagree with your position, but Frank Little strongly agreed with your thoughts. Who would you want to follow, Frank Little or me?

Pat Ireland

PS- I was one of the group who badgered Frank so much he finally did test the POI of the gun he had used to set a long run record with. After he saw where it shot, he could never shoot the gun well again.
 
#21 ·
There are a number of ways to do it right. zzt's explanation was great. Try 27-28 yards. It will throw a 20" - 22" pattern with a full choke.

The center of the pattern is easy to determine at that distance. I keep a record of how high each of my guns shoot at 28yards. I do it in "inches above aim point", not a percentage. My P-gun shoots 10" high at 28 yards. The center of the pattern is 10" above the aim point. It gives you a "standard" to work from and if you sell the gun you can tell the buyer how high it shoots at a given yardage. This 80% or 100% high stuff means nothing unless there is a yardage attached, and inches above POA is easier to understand. 0thers may argue, but thats how I do it.
 
#22 ·
Dove Commander - How can you convert 10 inches high at 28 yards to X inches high at 40 yards. If you use 0.357 inches rise per yard, you will be off by the fall due to gravity. Shot, leaving the barrel at 1200 ft/sec will fall three inches at 40 yards, but it will fall less than 1.5 inches at 20 yards.

Pat Ireland
 
#23 ·
Injecting shot fall at any distance into explanations concerning patterning a shotgun is mis-leading to most. Shot fall is measured ONE TIME and that's from the centerlines of the bore, not the bead, sights or a scope. If the barrel is leveled and centered on a spot at 40 yards then the charge falls approx. 3 inches for a 1200 FPS 1-1/8 oz. load below that aiming point. The regulation of shotgun barrels with ribs and beads negates mentioning shot fall at all. Same thing if a rifled slug is used in a shotgun or a rifle bullet as all begin falling as soon as it leaves the confines of the barrel.

Hap
 
#24 ·
Pat, I don't think I would ever care to know what my 40 yard POI is. I have found that I need to add or subtract shims depending where I'm shooting handicap. Maybe it's the background, or average height or speed of the target where I'm shooting. There is a reason. If I know my Perazzi shoots 10" high at 28 yards, and I shoot good averages with that gun, I can set up another gun to shoot 10" to start and I know I'll be close. Maybe my other gun is a K-gun, and it has a completely different feel and speed. I may have to tweak my POI a bit to get the loads centered at 27 yards. Maybe I swing it slower, or trigger speed, or maybe I just don't see the bird as well behind that gun. Required 27 yard POI has been a moving target for me. I've even added shims between banks if I'm not centering my hits or struggling. I think too many shooters play with loads and stats, when they should be working on their consistancy. When I shoot a good score, I document everything I did that day. My good handicap scores have been within 1 and a half shims of each other, but there are days I see the bird better too. I use the pattern board for documentation, and the trap field for testing.
 
#25 ·
Thanks for all the information. It is a subject that needs thrashing once in a while.Some people will gain confidenceby going through the stepps. for others it just puts a clinker in their thinker. Shooting really is a matter of eye sight and timing (brain processing the information and reacting to it.)and Fit of the gun. Real shooting begins when you are able to point and shoot without all the analysis.I to have to Laugh with all the mechanics of changing the combs and ribs. As you can see some are beyond that point. If you believe it is the dam guns fault,let one of the old time natural shooters shoot a round.Most of the time they will powder them without changing a thing. When your down, maby messing with adjusting makes some feel better. Marv White
 
#26 ·
Marv, Some may like to tinker with their guns. I for one absolutely hate to make adjustments. But, depending on your style, and target perception, a fixed rib and stock simply may not work. In my case, I started with a couple of Mod 12's and then a Citori O/U with adjustable rib. There was no way I would maintain my average in handicap without finding what POI worked best, but I had to have the ability to experiment. With a decent site picture, the Mod 12 would only shoot 6" high @ 28 yards, and I had to cover the bird at 27 yards. A K-80 and MX-10 also shot too low. When I got my current gun, capable of shooting 11" high or more at 28 yards, I was able to find my best POI and document it on the pattern board. To me that is the importance of a pattern board.
 
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