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Hey Neil Winston...

Discussion in 'Shooting Related Threads' started by Brian in Oregon, Dec 20, 2009.

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  1. Brian in Oregon

    Brian in Oregon Well-Known Member

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    Neil, are you aware of any tests of amount of shot vs choke size for pattern density?

    What I'm getting at is.... If you're shooting a good pattern with 1 oz of shot with a full choke at a certain distance, how much more shot would be needed to have the same pattern density at the same distance with a mod choke? Is there a formula for this?
     
  2. overbored

    overbored Member

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    I bet Rollin would know.
     
  3. phirel

    phirel TS Member

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    Brian- Due to the random nature of patterns I cannot see how any accurate formula could be derived. Also, to test this question, you must first define the term "good pattern" with numbers. My opinion is that if you have a good pattern with 1 oz loads, a similar load with 1 1/8 oz shot will give a better pattern. I guess it depends on if you are happy with good, better or best.

    Pat Ireland
     
  4. Neil Winston

    Neil Winston Well-Known Member

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    Man, what a great question, Brian, and why haven't I ever heard it before!?

    I think I've the data right here. It'll be provisional, subject to all of the above cautions, and a little bit off due to the fact that Shotgun-insight's scaling feature is linear but still OK if we don't go too far.

    Give me a day or two and we might come up with something interesting. There _is_ an easy way, and it will be fun to see how close that comes to reality.

    Neil
     
  5. Dr A C Jones

    Dr A C Jones Member

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    There is a really really easy way to get a working estimate.

    There is also a formula but it is complicated.

    It should be pointed out that one needs to decide at which part of the pattern the densities are to be equated, e.g. the very centre or some distance from the centre. Since a tight choke and a more open choke have different relative densities they can't be matched at more than one distance from the centre. (Being pedantic there are two distances from the centre where the pellet densities can be equal, but infinite distance from the centre giving zero pellet density doesn't exactly help the cause.)

    Andrew.
     
  6. Brian in Oregon

    Brian in Oregon Well-Known Member

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    My gut feeling is that the amount of additional shot may be more than what would be sanctioned for trapshooting, but we'll see what the math says. But for field use, like upland bird hunting or small game, this might be useful.
     
  7. zzt

    zzt Well-Known Member

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    Brian, here is my back of the envelope calculation. You don't give PEs or shot size, so I'll use #8 shot, and 75% for F and 65% for M.

    410 pellets in a one ounce load of #8. Full choke puts 307 of them (75%) in a 30" circle at 40 yards. The Modified choke puts 266 in at the same distance (65%). 307 / 266 = 1.154. 1.154 x 410 pellets = 473 pellets. The 65% PE with the M choke puts 307 pellets (473 *x .65 = 307) in the 30" circle at 40 yards, same as your 1oz with F choke.

    473 pellets of #8 weigh 1.154 oz. That's a little more than 1 1/8 oz, by 12 pellets. If memory serves, the ATA allows a 5% tolerance on 1 1/8 oz charges. If I recall correctly, that would place the maximum amount of shot at 1.18 oz, so this 473 pellet load would be legal.
     
  8. zzt

    zzt Well-Known Member

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    Interesting exercise Dr. Jones. If you match pellet count in 30", you get the same answer I gave above. However, you have 7 fewer pellets in 10" circle. You have 12 fewer pellets within the 20" circle. Is that enough to matter. I see and endless discussion coming.

    Brian, if you wanted to match the number of pellets in the 10" circle, you need 532 pellets to start with. You would also gain in the 20" and 30" circles.

    If you matched pellets in the 20" circle, you would need 506 to start with. There would be 3 fewer in the 10" circle, same in the 20" and more in the 30".

    In any event, they wouldn't be ATA legal payloads unless you went to smaller shot.

    And now I have another what-if game to play with Pattern Optimizer.
     
  9. Dr A C Jones

    Dr A C Jones Member

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    I used as my example matching the "pellets per target" in the centre of the pattern. In my trial, I used 70% PE as the start point with 400 pellets. Next I set 60% PE and needed to adjust the pellets to ~530 to get the same pellet density at the centre. Obviously, because the 60% PE pattern is wider, if its pellet density matches the 70% PE one in the centre, it must have a higher pellet density at any other distance from the pattern centre. Consequently, the higher pellet count payload gives a higher chance of striking the target. This is just a round about way of arriving at the conclusion that greater payload is better.


    Andrew.
     
  10. Neil Winston

    Neil Winston Well-Known Member

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    I don't think we've done this before, EE. zzt and Andrew have covered it as regards 30 inches and 10 inches, but I'd like to go back to Andrew's first statement, that in a general sense, it can't be done.

    Here's why, in a drawing on page 196 of John Brindle's book, "Shotgun Shooting."

    <a href="http://photobucket.com" target="_blank">[​IMG]</a>

    Imagine a pair of curves somewhere between cylinder and choke and that where modified is. The point is, there's nowhere you can draw a line to make the two kinds of patterns the same. Adding pellets to the the modified curve will not make it like the full; it'll just be modified with more pellets and with a different center density than the full at that distance.

    However, late-spring, we'll know how close zzt and Andrew got for their respective areas. I'm collecting 0.040 and 0.020 chokes from representative sources and should have a stable by April/May.

    I just had a good experience along these lines. I ordered the two (0.040 & 0.020) from Seminole Chokes last Friday night and said I would call early the next week with the credit-card information. I called on Tuesday and they were on my porch when I got back from the Minneapolis Gun Club on Saturday. I got a bit of a shock when I opened them. In their subdued black-oxide garb, they looked like 20 gauge tubes, but they are twelve, just dressed for a prom. They look fine and time will tell if they can be told from the others at the pattern board. I'll tell you, the workmanship on all these brands of tubes these days is beyond first-class, it's perfect and perfectly beautiful.

    Neil
     
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