1. Attention: We have put together a thread with tips and a tutorial video to help with using the new software. Please take a moment to check out the thread here: Trapshooters.com Tutorial & Help Video.
    Dismiss Notice

POI and pattern at 13 yards (Winston, photos)

Discussion in 'Uncategorized Threads' started by Neil Winston, Dec 11, 2005.

Thread Status:
Not open for further replies.
  1. Neil Winston

    Neil Winston Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,840
    There are a couple of threads active about POI, adjustable ribs, and so on. Here are some ways to find that out up close.

    I recommend 13 yards because, as you'll see, I can make some guesses about patterns at that distance as well. I also think that a bench rest of some sort is necessary, as just taking one shot at each "target" so you can keep track of what's going on and how you are doing. Paper, a wide magic marker, and no wind and you're in business.

    1. (After checking what's beyond your paper target to make sure it's safe - you won't be able see while you are shooing) Draws what looks like a ticktacktoe grid on the paper with the intersections about a foot apart.

    2. Mount your gun as usual and look at your "sight picture", that is how you see the barrel, rib, beads, and all that. Do it a few times so you can remember.

    3. With your bench rest (table, auto hood, stack of shell boxes - you get the idea) at a place where it puts your muzzle about 13 yards from the paper, sit down (I think that's important too) and put the gun up so you see down it in the same way you did when you were trying to get that right earlier.

    4. Use light 7 1/2 name-brand shells or your own good reloads of the same type. Putting the front bead _just at_ the base of one of the crosses at the paper make a shot. If you've been shooting long you jerked the gun as you shot and so you threw that shot away. So do it again, at another cross, and this time try to make a better, smoother trigger pull.

    5. If you are using a full choke you see two holes in the paper, one from the shot and the other from the wad. As testing continues, you'll see that the wad hole is upper-right now, then lower-left, then dead-center and so on and will then believe, correctly, that where the wad goes has nothing to do with where the shot goes so you can't us the was to tell where you are shooting.

    6.After a few shots, each at a different crosses, you'll have some holes (or little patterns) with a fairly consistent relationship to the crosses they were associated with. What to make of them? Well here are some and here's what they mean.


    We'll start with a Perazzi O/U Ithaca-era, top full and bottom less so.

    [​IMG]

    Individually they look like this, starting with the top one:

    [​IMG]

    This is what a full choke does; it just drills a hole with some pellets around it as well. You can't split hairs here, so this barrels shoots flat. (calculations to follow)

    Again, here's that O/U pair a little closer:

    [​IMG]

    And we'll zoom in on that bottom one:

    [​IMG]

    Now two things are apparent. First the pattern is lower in relation to the cross than was the one from the upper barrel. It started lower, so that can account for about an inch of it, but still, it _is_ lower anyway. Second it's not that nice round hole from the full choke, but rather it's sort of "lacy" and if you pushed the paper back it, a lot of it would still be there. This is typical of an improved modified choke with 7 1/2's at this distance, and that's just what this unmodified Perazzi has. Should we conclude that this barrel shoot low because we made this shot? Not, yet. Look back at that first picture again:

    [​IMG]

    On that one, the right-hand pair has the lower barrel shooting a lot closer to the cross, close enough that, considering where it started from, it shoots just like (but more open than) the upper one. You see, you can't go by any one shot, or, I think, even one day of testing. You have to do this a bunch of shots, and at least a couple of days, before you are satisfied (or ready to panic, whichever the case may be).

    That about covers the flat-shooters, here's a high one, my Bowen when I built the comb up to try it. It didn't work and I'm back down, but that doesn't say it won't work for you.

    [​IMG]

    Set up like this the Bowen shot eight or ten or more inches high at 40 yards. Yours will too.

    Let's close with a couple of more-average shooters. It's a Baker backbore and choke set for an MX-8 again. The top is 0.040 choke, the bottom is marked "16 yards." I've posted them together you can get an idea of the scale.

    [​IMG]

    Here’s the upper, the full choke, a blasted-away hole:

    [​IMG]

    The half-inch deviation to the side doesn't mean a thing; if it was twice that and over and over again, I'd begin to worry,but only begin to pending further testing tomorrow.

    And here's the 16-yard choke:

    [​IMG]

    It's way more open, isn't it? No holes, just a nice round pattern. This is how a modified choke shoots light 7 1/2's at 13 yards.

    How about where that Baker barrel shoots? It's about 2 inches high, I'd call it somewhat high, maybe 5 or 6 inches high at 40 yards.

    I'm going to take a break and take Kyra up to Metro for me to socialize and her to run. I'll fill this in with the rise vs. fall calculations when I get back.

    Yours in Sport,

    Neil
     
  2. zzt

    zzt Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    3,457
    Location:
    SE PA
    Neil, I'm curious. I can't figure out why you picked 13yds instead of say 16 or 20. What is significant about 13yds?
     
  3. Neil Winston

    Neil Winston Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,840
    nothing...it's just a place where you can (generally) tell one choke from another and I didn't try the others. Frankly, it's where the back of the traphouses line up at Metro so I don't have to measure the distance to the pattern frame every time.

    Neil
     
  4. zzt

    zzt Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    3,457
    Location:
    SE PA
    OK Neil (foot tapping impatiently), enough socializing. Where the heck is part 2?
     
  5. miketmx

    miketmx Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    2,961
    If a company such as Kolar says that a certain rib on their gun is designed to shoot 100% high does that mean that the center of the pattern shot at 35 yards will be 15 inches higher than the point of aim with a figure 8 or does it mean something else?? I'm just trying to verify the old fashioned term of percentage high. I agree that inches high is much more useful but what is the Industry Standard??
     
  6. JGS

    JGS Member

    Joined:
    Jan 29, 1998
    Messages:
    216
    I must confess I don't understand measuring pattern heights in inches as opposed to measuring percentages of shot above and below a target. To check a particular load or choke,I measure off 32 yards and then use a paper target with a bullsyeye marked in the middle of the paper. I then draw
    a 30" circle drawn around the bullseye and a
    second circle 22" around the bullseye. After shooting at the target,I divide the circle into quarters and then I
    count the holes in each quadrant. This gives me the information that tells me how high or low the particular load or choke shoots and how evenly the shot is distributed. I know one shot is not definitive so I shoot several more rounds to get a better feel of what I can expect. When someone tells me a gun shoots 70% high, for example, I understand that 70% of the shot is above the target at the distance shot and 30% of the shot has gone below the target. I can visulize what happened and adjust the gun accordingly,if required. When someone says a gun shoots 4 inches high, for example, I'm not sure what this tells me in terms of what the pattern looks like and how much of the shot is above the target and how much has gone below the target. I'm missing how one uses inches as a useful measurement in determing what a shot distribution looks like and I thinking we pattern to check where the gun is shooting and how dense or open a pattern may be. Of course, I still think "dram equivelent" is a better way to describe the powder charge in a shell. What useful information is communicated when patterns are measured in inches. Thanks for the education.
     
  7. zzt

    zzt Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    3,457
    Location:
    SE PA
    jgs, 70/30 or 90/10 is meant to convey Point Of Impact information, not pellet distribution or pattern size information. The trouble with percentages as you describe is they don't really tell you anything you can use. 70/30 describes how high a gun shoots with a specific choke at a specific distance. It doesn't tell you where the gun will "shoot" with a different choke, or at a different distance with the same choke. With a full choked gun, a 70% high pattern describes different Points of Impact at 10 or 30 or 40 yards, because patterns do not develop linearly.

    The beauty of a linear dimension is that it gives you information you can extrapolate from. Choke is not a factor. If you know how high the center of your pattern is at any given distance, you can calculate the height for any other distance.

    Here’s an example. Suppose the center of your barrel is exactly 1” below your bead. You stand 16yds away from a target and put your bead directly on it. If you hit the cross hairs dead center, your gun is pointing 1” high at 16yds. It points 2” high at 32 and 3” high at 48. This is useful information. If it hit 1” high at 16, your gun points 2" high at 16yds, 4” high at 32, and 6” high at 48.

    Factor in trajectory and you can calculate your actual POI. With your gun pointing 6" high @ 48yds, 7 1/2 shot fired @1200fps will drop a touch more than 5" at that distance, so your gun actually shoots 1" high. The center of your pattern is 1" above Point of Aim at 48yds. The shot drops about 1.5" @ 30yds, so your POI is about 1/2" above POA at that distance. That's much more precise information than 60/40 or 80/20.
     
  8. hmb

    hmb Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    9,406
    zzt - Does gravity have any effect on the shot? HMB
     
  9. zzt

    zzt Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    3,457
    Location:
    SE PA
    HMB, thanks. I was puzzled by your question until I reread my post. An entire paragraph didn't get copied across. I'll go back and add it, plus edit for more clarity.
     
  10. Harold

    Harold TS Member

    Joined:
    Jan 29, 1998
    Messages:
    247
    JGS,

    There are at least three things wrong with your method.

    First, if you change to a more open choke, there will be more pellets scattered below the POA, so you will get a different result.

    Second, you may think you know what someone means when they say a gun shoots “70% high,” but you really don’t. There are several ways to make this determination. They could be using the same method you are using or they could be using the “3 inches = 10%” method where “70% high” means that the POI is 6 inches above the POA. If you know they are using the “3 inches = 10%” method you will still have to find out if they mean at 35 yards, 40 yards, or some other distance.

    The third problem is that you are wasting a lot of time counting pellets, which is totally needless for determining where your gun shoots. Just find the center of the pattern and measure the distance from there to your bullseye. That’s all there is to it.
     
  11. Neil Winston

    Neil Winston Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,840
    Mike TMX, there's no industry standard as far as I know. When I ordered my gun from Bruce Bowen I said where I wanted it to shoot, in inches, and it did. Why would I have done it any other way? As Harold said, a ruler tells all in about 5 seconds - it's there or it isn't. Especially since you can't ever get really 100% high without going way over - some pellets will spread down no matter what. Try the link above and see how insensitive the percent system is at any of the extremes since so few pellets are moved in a round, thin pattern at the edges.

    Kyra and I have been working on our Christmas card and I've neglected my promise to say how I calculate POI from my 13-yard "holes"

    Scroll up to the over barrel of the O/U and see what I call a dead-on shot. OK, maybe a bit one way or another, but for the purposes here - comparing it to others - it's dead on. How did it get there? And how do we take gravity into the calculation.

    From the top of the bead to the center of the bore on this MX-8 is about half an inch. So getting to the center of the cross, it shot "uphill" about half an inch.

    Now we will subtract gravity to see where it would have shot without it. Well gravity caused the shot to fall about half an inch getting to 13 yards, so this gun "really" shot an inch high, the half inch you can see and the half inch you can't see, the gravity-obscured one.

    So this is a 1-inch high shooter at 13 yards and will shoot 3 inches high three times farther away which is 39 but we'll call it 40 yards. But now we have to add gravity in again, and at 40 yards the shot will fall 3 inches and again center its pattern on the cross. In other words, a gun that shoots like that over barrel, dead on at 13 yards, will continue to shoot about the same wherever you point it.

    The lower barrel (and this goes for unsingles, in principle and you have to take this into account when shooting the close for POI) started about 1 1/2 inches low and, at least in the right picture, also hits about on the cross, So it raised an inch and a half, plus half inch it fell, that makes it a 2-inch-high shooter. Multiply by 3 to get 6 inches, put the "minus 3" of gravity back in and you get a gun which shoots about 3 inches high at 40 yards, and shoots like this "a little high" all the way out again.

    Lastly, let's look the Bowen set up to try, for a while, a "high shooter." The center of the bore is 3/4 from the bead, it shoots - what - 3 inches high? So without gravity that's 3 1/2 and it started down 3/4 and adding we get 4 inches (OK 4 1/4 but we do this to realistic precision). Multiply 4 by 3 to get 12, subtract 3 and we predict 9 inches high for a POI at 40 yards. And it _was_ about there, maybe an inch lower.

    In short, close-range POI testing works, is fast and economical of time and paper and ammo, and gives results you can scale to shooting distances and be pretty close to right.

    Yours in Sport,

    Neil
     
  12. waverider

    waverider Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    1,619
    Location:
    HI
    Neil,

    Just as I suspected on how you got the 13 yard distance. Only I still have the suspicion that you discovered it by shooting the traphouse. LOL 8^)

    Jason
     
  13. marotta

    marotta Member

    Joined:
    Jan 29, 1998
    Messages:
    155
    Neil,

    Excellent information..... this information makes it very easy for me to understand POI. The web site is superb.
     
  14. porky

    porky TS Member

    Joined:
    Jan 29, 1998
    Messages:
    1,267
    The 13 yard test was as famous test to determine point of aim.It is called the Churchill test and it saves a lot of time in determining the point of aim.It's like setting up a scoped rifle starting at 25 yds instead of 50 or 100 yards.It's just a lot easier to test the pattern.
     
  15. Jim101

    Jim101 Active Member

    Joined:
    Jan 29, 1998
    Messages:
    1,942
    Location:
    Knob Noster, Mo
    Actually I think the Churchhill test was done at 16 yards. He said at that distance a 1/16 inch comb adjustment resulted in a 1 inch change of POI at 16 yards. Jim
     
  16. jrmb

    jrmb TS Member

    Joined:
    Jan 29, 1998
    Messages:
    31
    yes fantastic post! thank you.
     
  17. grunt

    grunt TS Supporters TS Supporters

    Joined:
    Jan 29, 1998
    Messages:
    5,914
    Location:
    Thousand Oaks Ca
  18. Dove Commander

    Dove Commander TS Member

    Joined:
    Feb 21, 2007
    Messages:
    1,364
    If Neil types like me, it took him an hour to post all that. Thanks for taking one for the team Neil. Excellant post.
     
  19. BigM-Perazzi

    BigM-Perazzi Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    8,542
    Location:
    HELL, MICHIGAN
    So much information!!!!
     
  20. jalu

    jalu Member

    Joined:
    Jan 29, 1998
    Messages:
    52
    jalu storing this info.
     
Thread Status:
Not open for further replies.
Search tags for this page

13 yard shotgun patterning

,

13 yard shotgun patterning for trap and adjustable comb

,

neil winston patterning

,

neil winston point of aim

,

neil winston shotgun

,

patterning a trap gun at 13 yards for poi

,

poi at 13 yards

,

winston 13 yards patterns