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13 Yd POI revisited

Discussion in 'Uncategorized Threads' started by 5screw, Apr 30, 2007.

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  1. 5screw

    5screw TS Member

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    Ok, I tried the 13 yd thing over the weekend. For years I have been shooting my patterns at 40 yards. I normally use the tighest choke I have and shoot 5 shots so that the pattern is thick enough to easily see a center. Then I measure from the aiming point and determine how high in inches the pattern center is. After going through this procedure again on Sat. I determined my point of impact was 9 inches high at 40. Decided to try the 13 yd test and found that the point of impact was only about 1 3/4 inches up Repeated several times with same results. Now according to the 13 yd advocates that should have been at least 3 inches up, right? Did not shoot off a bench cause I don't shoot trap from a bench. I know the pattern is 9 inches high so that makes me suspicious of the 13 yd theory. On Sun. at the local club a 5 stand shooter was patterning his Beretta sporter and was upset that the upper barel was shoting higher than the bottom. I looked at his pattern sheets and he was right.
    Since he only shot one shot per sheet I suggested we try the 13 yd test and found there was only about an inch difference in the bbls but his top bbl patterns were clearly 4-5 inches higher at 30 yds. So explain this to me.

    Bob
     
  2. miketmx

    miketmx Well-Known Member

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    "Did not shoot off a bench cause I don't shoot trap from a bench. I know the pattern is 9 inches high so that makes me suspicious of the 13 yd theory."

    If you did not use the rest then your methods are not without question. Incidentally when I bore-sighted my MX-3 it looked like the bottom barrel would shoot higher than the top barrel but when I patterned the gun at 13 yards and at 35 yards the reverse was true and I used a rest in both cases. The MX-3 is designed to shoot top barrel first.
     
  3. miketmx

    miketmx Well-Known Member

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    Shawn there may be a penalty yardage at the Inland Empire but I haven't heard anything yet.
     
  4. Neil Winston

    Neil Winston Well-Known Member

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    5screw, understand that if you doubt the "13-yard theory" you are just doubting Newton's First Law which, in this case, says that things fly straight (discounting gravity - and gravity would only make your results worse.)

    I think the problem you are having, bench aside, is your way of determining your POI at 40 yards, the five shots you mention. Doing it that way you miss out on very important information, namely, how well are are able to put shots in the same place.

    Remembering that there is no such thing as the law of averages as it is conventionally understood, - see link above - if you shot five times and look at them individually, you would see that they move around - some up, some more left, and so on. A shot or two a little high will raise your "composite" POI which is what I bet is happening here.

    The alternative explanation, that your shot is being made to rise in a manner greater than it's normal trajectory on the way from 13 to 40 yards is so unlikely I think we can dismiss it out of hand.

    Neil
     
  5. GunDr

    GunDr Well-Known Member

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    Neil(Quote)"I think the problem you are having, bench aside, is your way of determining your POI at 40 yards, the five shots you mention. Doing it that way you miss out on very important information, namely, how well are are able to put shots in the same place."


    "Remembering that there is no such thing as the law of averages as it is conventionally understood, - see link above - if you shot five times and look at them individually, you would see that they move around - some up, some more left, and so on. A shot or two a little high will raise your "composite" POI which is what I bet is happening here."

    Neil,

    Are you saing that checking a POI using multiple shots is bad or OK? What will shooting a single shot at paper, using mutiple pieces of paper going to tell you...besides each shot may very a coulpe of inches. Using the same load, benchrest etc, if variations show up in the patterning, there's not a whole lot that can be done about it. Why not take an average of three or four shots.

    By the way, I sent you an email, did you get it? I'd like to know your opinion of it.

    Doug Braker
     
  6. Neil Winston

    Neil Winston Well-Known Member

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    Doug, the underlying idea with multiple-shot-on-one-paper is that "everything will average out," that a shot pulled to the left will be countered by one to the right. But that bad shot has no rubber band to bring the barrel to the right for the next shot, all you have is a total effect more to the left than it should be.

    Sure it's hard to tell pattern center at 40 yards, often there doesn't appear to be one. But you can get a general idea.

    I think in 5screw's case he might find he's not all that good at placing a round bead at the base of a cross offhand at 40 yards and he'd be less confident of his pattern height at that distance.

    I'll check my laptop for that email and answer it, Doug. I often miss a few on the road because I never see them again. Sorry.

    Neil
     
  7. GunDr

    GunDr Well-Known Member

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    I do understand when you're describing the one shot "pulled to the left", but I also don't like to rely on just one patterning sheet either. By having 4-5 sheets to compare to one another, can give you a more "accurate" average.(?)

    Doug
     
  8. Neil Winston

    Neil Winston Well-Known Member

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    Doug, at 40 yards I use the Shotgun-insight program to determine center of pattern and even off a rest I'm none too good. That's why I use 13 yards - just yesterday I went through a box and a half for shells testing a combo, so you can guess what I think of the couple of shots most use.

    Say you plan to take 5 shots, all at the same "cross." Three are right in there, dead where they belong. The fourth is left, the last correct again. With multiple shots, you will think the gun shoots left at least some; with individual patterns, you will know correctly that it shoots just fine.

    If you did the multiple-shot test several times, then it would weed that one out and you would again have the right answer. So I have no reason to doubt those results.

    But I could have gotten the same information easier, faster, and with less uncertainly, just by moving forward. If there is an more than a breath of wind then close is the only way to go. Shot drifts like crazy.

    Neil
     
  9. 5screw

    5screw TS Member

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    Well "in 5screws case" he is quite confident in his ability to hold at 40 yards. In any event when I check for impact it never is a one time deal on one day only. The beauty of the multiple shots on the paper is that a true center will show its self. Pulled shots will show up as thin edges and although there may be pellet holes well to the right or left or even up or down, in the long run the core center is quite obivous. I know for a fact the gun in question shoots 9 inches high at the stock setting I use. The question is why did it not correlate with 13 yds. I did not take into account the distance between the center of the bbl and the top of the bead. That would bring it closer to being correct. What you all are failing to take into account is that at some point the shot charge has to cross the line of sight going up, and at some point cross again going down. Probably at that range though there is no pattern left however. Different loads and speeds will change where that close crossing point will be. 13 yds. may be farther or closer to the crossing point. If I want to know where my pattern is at 40 yards I have to shoot it there. Try sighting in your varmint rifle at 25 yards and guess how many woodchucks you'll hit at 300yds. I have shot hundreds of patterns and counted thousands of pellet holes over the last 40 years. Its never to late to learn however, but try the multiple shots method and if you have no confidence in your ability to see a center, shoot 10 shots. Bet you will then.


    Bob
     
  10. phirel

    phirel TS Member

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    When shooting 10 shots at 13 yards on 10 different sheets of paper is it not uncommon for me to see three that I have pulled to the left. As Neil explained, if I shot all 10 shots at one piece of paper, it would appear that the POI was a little to the left of the true POI.

    Also, shooting from a bench is important. I recognize that we do not shoot trap from a bench but the purpose of determining the POI is to see where the gun shoots, not where we shoot the gun.

    Pat Ireland
     
  11. Bob Hawkes

    Bob Hawkes Well-Known Member

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    Boy am I thick! Thank you Neil, the light finally went on. I also had been doing multiples, covinced in my pea brain that I was getting a true average. Now it's back to the paper one at a time. Thanks again. Bob H.
     
  12. GunDr

    GunDr Well-Known Member

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    I guess I don't mind the walk at 40yds!! If the day decides to be windy, I do move up.

    Doug
     
  13. zzt

    zzt Well-Known Member

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    5screw, from an unsingle with center of bore 1.5" below the bead, using a 3dram 1 1/8 oz & #7 1/2 @ 1200fps, the shot crosses the line of sight at 14.5 yards and recrosses at 45 yards. The center of the pattern is never more than 2/3" high or low from 14 to 50 yards, and .4" high at 40 yards.

    If you hit the cross hairs at 13 yards with this gun and load, you will be .8" high at 40 yards. Hit them at 16 yards (a couple inches shy actually) and you will be dead on at 40 yards.
     
  14. AJ100

    AJ100 TS Member

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    MAN, somewhere around the seventh or eighth post my head started to hurt.

    ALL good advice but, whew!

    AJ100
     
  15. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    Hey guys! Just because there happens to be a hard wind blowing, pattern away! It may come in handy one windy day? Hap
     
  16. Neil Winston

    Neil Winston Well-Known Member

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    5screw, oversingle? Standard rib height? Unsingle?

    Neil
     
  17. Jollytrapshooter

    Jollytrapshooter Member

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    I don't really understand the concept of the "13 yard theory". You don't shoot the bird from 13 yards, and you don't shoot trap off of a bench, and as far as seeing where the pattern is, I want to know what my pattern is doing when it hits the bird, not when it's 3 yards from the back of the trap house. I see no real use/point in finding what your pattern does at 13 yards. I'm not trying to contradict anyone, but I just don't get it. When you shoot trap, it may be windy out, it's not always going to be perfect, so you want to know what your pattern does when the weather isn't perfect. Doesn't this make sense? Or am I just missing a MAJOR point somewhere?

    -Jollytrapshooter
     
  18. Bustedemall

    Bustedemall TS Member

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    I'm glad 5screw posted his thoughts on this because I've been thinking along the same lines. In fact I tried the 13yd poi and it just didn't work for me either. I have a background of 30 years of competition shooting in several different disciplines but see myself always as a beginner. Anyway, in no particular order these are my observations given in the spirit of open and friendly discussion with respect for all opinions and positions.


    It's been repeated that most right handed people shoot patterns to the left when shooting offhand, this is used as a reason to use a bench. If you shoot to the left offhand shouldn't you fix THAT problem? Checking the gun on the rest and finding it shoots straight off the bench fixes nothing. I've found lots of right handed people shoot high and to the right, and others that shoot low left, showing different types of flinches and lack of trigger control. If you don't fix the shooter they won't be a bit more successful at hitting birds in the long run even after you've set the poi off the bench. If you compensate the poi for poor technique a situation is set where the shooter is rewarded for doing it wrong and punished for doing it right which will limit their development. In other words if you move the comb over to compensate for a flinch the shooter will hit the bird when they flinch but miss when they don't, not a recipe for success.


    If you can't stand and shoot a decent group at 30 to 40 yds offhand how do you expect to consistently hit a moving bird at the same distance? Any type of gun that recoils much could have a different point of impact if it is shot off a bench. Off the bench all the recoil has to go straight back and upwards off of the bench because it is solid , shot off your shoulder it has more directions to take off in. If you are very careful in your set up you can minimize this however. It is also difficult to duplicate your head position, cheek weld, how you see the bead, and how you mount the gun standing, while sitting at a bench you find at most shooting ranges. I'll give you that if you are a trigger jerking flincher you will get more consistent results, but with those problems you have more serious issues than establishing your poi. In fact I submit if you can't consistently, hold, press the trigger, and follow thru properly you may not find the true point of impact for your firearm anyway. To illustrate just try to help someone set the sights on a pistol who is jerking the trigger and flinching, it's practically impossible. I don't mean to be harsh but shooting ability is what it's all about. I'd be willing to bet that the best trap shooters can stand there at 40 yds and shoot consistent point of impact patterns and will call a shot bad if he or she shoots one that won't be in the "group". A competent shooter should be able to do that also but maybe not quite as easily as the best but still be able to call the bad shots.


    As mentioned earlier you can't set your scope on a rifle at 25yds and then extrapolate to 300yds and expect to really be sighted in at 300. Yes, a shotgun is not the precision firearm that a rifle is but we regularly talk about changing our poi 2 or three inches higher or lower to really smoke the birds so maybe trap shooting is more of a precision event than it looks?


    Why can't you determine the center of a pattern? We've done it for years and it doesn't seem that hard. Nothing is perfect but where do you want your error to be? The errors can be in determining the outer circumference of a set of patterns shot from 30 or 40 yds and then dividing the pattern in half and measuring to the aiming point. Or the errors can be at the 13 yd line with the geometry increasing the errors exponentially and not knowing what is happening at the distance your shot is going to encounter the target.


    The majority of trap shooters seem to believe the beads should be used to check the gun mount and then ignored, all focus goes to the bird and the gun has to shoot where you look. Therefore the poi should be at that point where they look. I'm not referring to how much of the pattern is above the point of aim but where the shooter is actually looking and expecting the bird to break at. Why then would you set the front bead just under a mark on the cardboard at 13 yds to determine if the gun will shoot at 40 yds where you are looking for it to? If we are not aiming with the bead then how do you use the bead to check the poi? Using the preferred shooting method the actual point of aim will be at some point above the bead, the question is how much above the bead? And the tough question would be how much above the bead at 13 yds since we never look at a bird over our shotgun at that distance in trap shooting? Again geometry is going to increase any error. Add to this how much above your point of aim you want your pattern to actually hit such as 70/30 or however many inches high you want.


    I'm truly not trying to confuse or make this more difficult than it is but these are the factors we are dealing with. No wonder so many just set the trap on straight-aways and adjust the comb until they smoke them and call it good. I don't think you can fault that method at all.

    If you can't shoot offhand instead of using a bench you might try a step ladder if you can find one about the right height. You should be able to shoulder and hold the gun in the same way you shoot at a bird and just use it to steady yourself a little. I would still shoot at the distance I expect to break a bird.


    There are even more factors I can think of but this is enough for now. I hope that Neil doesn't take this as an attack on him or his method because it certainly is not meant as that. I have much respect for his writings and obviously this method works for him and others. I just couldn't make it work for me and want to learn more about setting up a shotgun in general. Hopefully we can all learn something in this thread. I do have one question for Neil, you referred to Newton's law and that shot "fly's" in one post, could you explain that please? I think Newton's second law is about objects staying in motion but I didn't think that shot actually fly's? :)
     
  19. Cherokee Kid

    Cherokee Kid TS Member

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    Let me make this simple. If you want your gun to shoot higher than your point of aim so that you can always keep a rising trap target above your barrel, do EXACTLY what Neil says to do at 13 yards. If you want to both remain and appear ignorant of the geometry and ballistics involved, argue against it. It is amusing, but sad.
     
  20. 5screw

    5screw TS Member

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    Neil:

    The shotgun I am using is a Perazzi MX 9 O/U 31 1/2". The other guy's gun is a Beretta sporter. I make no claims to know anything about it. I thought both when shot at 13 yds did not show what they did down range. But even though I have patterned extensively for years this 13 yd stuff is new to me and perhaps I do not have the techinque down right. I do have complete confidence in the 40 yard method. By the way, we shot together at the Iowa state shoot last summer. I was the Indiana guy that was your number 5 man for at least 3 or 4 events. I enjoyed it very much.

    Bob
     
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