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Patterning @ 13 yards- skeet gun?

Discussion in 'Uncategorized Threads' started by skeet_man, Jan 24, 2008.

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  1. skeet_man

    skeet_man Well-Known Member

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    I guess this post is mainly directed to Neil, but maybe others can answer as well.

    Do you think the 13 yard patterning technique you advocate for determining POI for a trap gun will work equally as well for a skeet gun?

    The reason I ask is I believe my gun shoots high, but patterning for spread or POI at distance (20 yards) is fairly inconclusive for me using skeet chokes (the only chokes I have for this gun, and buying additional chokes for patterning purposes isn't an option). The only way I think you could accurately determine POI outside of your method would be patterning @ 20 yards, then draw a circle originating from the center, then an equal sized circle originating from the center of the pattern, then determine the difference from 50/50 to determine the actual POI. The only problem w/ this is there is no way you can accurately determine the exact center of your shot pattern, and this problem seems to be is compounded if you are using paper that’s just barely big enough (36" square) (plus your method seems ALOT quicker,,, and there’s no pellet counting!!).

    What I’m thinking of doing is patterning using your method. However, I’d substitute 10 yards for 13, as I can easily double the distance to get the actual distance I’m determining POI for (20 yds), plus the shorter distance would help keep the patterns of the open chokes tighter. For example, lets say the POI is 2" high @ 10 yards. Add to this what gravity took out (+.75" @ 10 yards) to get 2.75". Multiply by 2 to get POI @ 20 yards, then add gravity back in (-1.5"). So to go back to the example, 2" high @ 10 yards would correlate to 4" @ 20 yards (for the top barrel). For the bottom barrel (due to the barrel being 1/2" apart, based on your previous posting), 2" high @ 10 yards should be 5" high @ 20 yards.

    Am I on the right track? I'm thinking that once I accurately determine the POI of my gun, then I can more accurately test it for pattern, as far as testing loads vs. each other, because I will better know where I need to draw my circle (or shoot lower enough of the paper that the center of my pattern will be in the center of the paper).

    Thanks for your time and consideration.
     
  2. mercedesman1981

    mercedesman1981 TS Member

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    Thirteen yards was used as it is 1/3rd the average effective distance (40yds) one expects to be able to break a target.

    The effective skeet range is about 25yds, so 8 yds may be the POI distance you may want to try to test at.

    Mike
     
  3. hmb

    hmb Well-Known Member

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    The longest shot in skeet is 21 yards. What gun are you using? HMB
     
  4. zzt

    zzt Well-Known Member

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    Not true. In doubles from 3, 4 and 5, the second shot is 22-23 yards.

    Skeet, 13 yards is fine. I like to float the bird, so my gun shoots 60/40. That's 3" high @ 40 yards. So shoot for POI at 13 yards and when the center of your pattern is 1" above POA, you are done. Use a tighter choke to make determining the center easier.
     
  5. skeet_man

    skeet_man Well-Known Member

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    If my previous tests are correct, i'm shooting about 3" high @ 20 yards on the bottom bbl (70/30 to 75/25) (again, this is if I'm doing it correctly), whatever it is, it works well for me, I just want to know once and for all where it really is shooting.

    Therefore, if the center of the pattern is 3" higher than the aim point, and I draw a 26" circle originating @ the center, I've covered 3" at the bottom of the pattern where there shouldn't be any shot anyways, but missed 3" of the top of the pattern, horrifically skewing my actual pellet #s, which I think is the reason why i've never been too successful at patterning, I may be missing 10% of the pellets I should be counting.

    When I shoot for actual patterns (not POI), i'm going to be looking for 26-28" diameter circle for 20ga, i think 22-24 for 28ga, and 18-20 for .410, most of the shot in that circle @ 20 yards (I shoot fairly quick so i'm not chasing anything past 21 or 22 yards usually).

    7 yards may be better than 8 or 10 for determining POI (3x7=21), just to keep the pattern tighter.

    I'm checking POI on kolar subgauge tubes in a kolar gun, and at $85/choke, buying tight chokes just to determine POI is out of the question.
     
  6. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    Give this a little thought and consider sighting in a rifle bullet?

    "Add to this what gravity took out (+.75" @ 10 yards) to get 2.75"."

    If you did all this subtracting business for gravity fall, you'd never be able to sight in a rifle,, or a shotgun or a shotgun with slugs. You only subtract gravity fall once whether it be an apple or a grape! Hap
     
  7. zzt

    zzt Well-Known Member

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    Look Skeet, you are making it harder than it has to be.

    First, 60/40, 70/30, etc. have ZERO/NADA/NOTHING to do with the percentage of pellets. Used correctly it expresses the percentage of PATTERN above the Point of Aim at 40 yards. So a 30" diameter PATTERN centered 3" above POA @ 40 yards is said to be a 60/40 shooter, because 60% of the pattern AREA is above the POA.

    You say you gun shoots 3" high @ 20 yards. That's 6" high @ 40 yards, and a classic 70/30 shooter. The 3" high number is what counts. Everyone understands that. Not many will correctly interpret what you mean if you say 75/25, because they won't know how you are calculating that. Geez, we still have people on this site who shoot for POI at 13 yards with a full choke and claim their gun shoots 95/5 because that's how many pellets were above and below POA. Then when they move back and pattern, their supposedly 95/5 gun turns into a 60/40 gun, because of the placement of the pellets. How can that be, logically speaking? It cannot. So it is much easier to say my gun shoots 2" above POA at X yardage. Then everyone can calculate where it shoots at any other yardage.

    Draw a circle, centered on your pattern sheet. If you are interested in a 24" diameter area, draw a 24" diameter circle. Put an aiming dot 1 1/2" below the center of the circle. Stand 10 yards away, aim at the aiming dot, and your pattern will be centered (assuming you are correct about your POI being 3" high @ 20yds). I suspect you will want to evaluate a smaller diameter at 10 yards.
     
  8. Neil Winston

    Neil Winston Well-Known Member

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    skeet_man, your plan looks fine to me, except your gravity correction, where the values you are suggesting are way too large.

    The fall at 10 yards is just 0.1 inches and even at 20 yards, only 0.6 inches. I think the gravity effect, important at trap, can well be ignored for this up-close skeet POI testing. Otherwise, go for it.

    Neil
     
  9. skeet_man

    skeet_man Well-Known Member

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    Neil- Thanks a bunch for your input. I didn't think the gravity effect would be much at skeet distances, but I tried to mirror your procedure as much as possible by piecing together what you wrote on a couple different threads. Now to wait for good weather.....
     
  10. skeet_man

    skeet_man Well-Known Member

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    Also, if I could bug you with one more question, how did you come up with the .1 and .6 figures as far as gravity's effect on the pattern? I spend about an hour on google last night to try and figure out what the drop would be @ a given range, and came up with nothing.

    Thanks a bunch again
     
  11. Neil Winston

    Neil Winston Well-Known Member

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    s_m, let's do it together.

    The Formula I learned was S=1/2 a (T-squared), where S is the distance covered, a is the acceleration due to gravity (32 feet per second per second, the latter because it's an acceleration) and t is the time, which is this case gets smaller when squared since it is less than 1.

    Let's say the average speed over ten yards is 1150 feet per second, so it gets there in 30/1150 second or about 0.026 seconds which squared is 0.00068.

    Multiply that by 32 (= 0.022) and one-half and get 0.011 feet.

    Multiply that by 12 (to convert to inches) and get 0.13 inches.

    The twenty-yard drop is handled the same way, using an average speed of perhaps 1100 ft/sec.

    Neil
     
  12. skeet_man

    skeet_man Well-Known Member

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    Makes sense to me, thanks a bunch!. I'll put this information in my shooting binder i'm in the process of building.
     
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