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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.
 
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
 
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
 
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.
 
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
 
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.
 
Pat Ireland,

I was answering the original question of how to pattern a shotgen; not how to pattern and select particular loads. I have shot trap for 40+ years. Early on, I determined that the most importand thing in trap shooting was the proper sight picture combined with correct lead for the angle of target flight. Choke and shotshell loads are of secondary importance. The more I shoot trap, the more I have found this to be true.

Dennis
 
Pat Ireland: I'll follow you only because Frank Little has passed away. I do have his book and will always remember what a great person he was. I respected, not only his talent, but he worked a fulltime job and I could relate to that (with the exception of me being a great shot). Darrell
 
I did some very professional patterning of my own last weekend. I wanted to compare cheap factory loads to reloads with cheap shot to reloads with magnum shot. I used the professional method of paper plates tacked to a tree at 35 yards all through the same choke all 7 1/2 shot with my 20 gauge then counting the holes in the plates. What did I find out? There were wild inconsistancies with the cheap reloads and the cheap store bought shells. They patterned the same. But the magnum reloads were more consistant. Whereas the cheap shells would have anywhere from 15 to 35 pellets through the plate the magnum shot always had between 25 and 35 pellet holes. The magnum shot did not have the wild swings that the cheap shells had and had more even distribution of pellets. I have decided to spend the extra 5 dollars per bag on the magnum shot. I know my best scores in competitions were with my magnum reloads.
 
Dennis- I am just getting old and fussy about words and for this I apologize. A pattern for a shotgun would be a set of drawings used to build the gun. A pattern for a load shot through a shotgun would be a bunch of holes. You can test how a specific gun patterns a load, but this is very different from "patterning a shotgun".

Pat Ireland
 
Thanks, highflyer, you've done the work to give us some valuable information. I've done some of this myself with "cheap" vs. "premium" loads and sometimes I get what you did, sometimes not, though. Before buying a season's loads it's a test well worth doing. If you opt for bargain loads you might end up with something just fine - or you might get something not worth shooting. And they could come from the same maker in the same boxes.

Neil
 
Neil- Your explanation, and I agree with you, presents a dilemma to me. I have tested, and shot a few flats of a discount shell made In Italy with a brass head and a picture of the Roman Coliseum on the box. To get them at the best price, I must order a pallet. But, I might not get what I tested and I don't want to get stuck with 100 flats of bad shells. Life decisions can be difficult.

Pat Ireland
 
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