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Tight choke

Discussion in 'Shooting Related Threads' started by twcpdc, Dec 13, 2010.

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  1. twcpdc

    twcpdc Member

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    Looking into a MX8 on here lister says top barrel is 726 bore choked to 680 for 46 choke. I was under the impression that about 40 should be max choke for shooting maybe some thing like this for games. Does anyone out there know what a 46 choke would do I know no two guns are the same But I am a little concerned about that much choke I would use the gun for sporting clays and some bunker Thanks for any help Tom
     
  2. timb99

    timb99 Well-Known Member

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    My unsingle barrel is choked 0.042 (0.728 to 0.686)

    Works fine.

    According to Dr. Andrew, there's not all that much difference in patterns from 0.030 to 0.050.
     
  3. Bob Hawkes

    Bob Hawkes Well-Known Member

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    Tom, I would think it might work well for Bunker IF you're using the lite international loads. Bob
     
  4. Neil Winston

    Neil Winston Well-Known Member

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    Tom, I get what was reported above: 0.040 produces, in general, the tightest patterns. Here's an example with three Perazzis shooting Heavy 7 ½ Federal papers.

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

    Before you worry, check out the y-axis label and see that the difference between the 0.048 gun and the very good RP gun with 0.040 is only about 3% and you would never tell this except by counting pellets.

    Neil
     
  5. Jawhawker

    Jawhawker TS Member

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    The gun in question will break alot of targets and as Neil's graph depicts, not enough difference to concern yourself with. I had several early Pguns that had choke constrictions in excess of .050. Had quite a few 200's and 100's in doubles with them.
     
  6. timb99

    timb99 Well-Known Member

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    Here's what Dr. Jones had to say whan I posted about the choke restriction on my gun. This seems to match well with what Neil and pheasantmaster have to say:

    <i>From: Dr A C Jones <br>
    Email: <br>
    Date: Thu, Aug 19, 2010 - 12:36 PM ET<br>
    Website Address:

    I did a lot of testing with ~30, ~40, and ~50 thou. By testing I mean proper numerical tests. There wasn't much between them. With some shells the 40-thou gave patterns a little tighter than the other chokes. With other shells things reversed - but not by much. The safest bet for the tightest patterns with the least amount of risk and effort seems to me to be something ~40-thou. But a little bit either way will not make much difference.

    Andrew.</i>
     
  7. phirel

    phirel TS Member

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    Tom- Another thought. You were told the barrel has 46 thousands constriction by the person selling the gun. But, did he really measure it or was he told that by another person? His information might not be accurate.

    Pat Ireland
     
  8. benniesdad

    benniesdad TS Member

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    I may be out of my league asking this, but how would variations in payload and velocity influence the pattern density results mentioned?
     
  9. Neil Winston

    Neil Winston Well-Known Member

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    There's one more thing I like to point out about this graph because it ties in with Andrew's phrase "Proper numerical tests."

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

    While the average difference between 0.040 and 0.048 in this test is 3% and between 0.048 and 0.033 is less than a percent, the range for the ten tested shells is, on the average, about 12 percent. That's why you could never tell by shooting them; you have to count. The data don't come in in the nice smooth order you see here, but first a "Good" on of those, then a "Bad" one of those and a lot of the time, looking at a pair or a few, the results are the opposite. Data like these only show up on graphs; in the "real world" they might show up as a bird or two in a lot of birds, or not show up at all.

    I'd have no worries at all about the gun Tom is thinking of.
     
  10. Neil Winston

    Neil Winston Well-Known Member

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    Benniesdad, not much. You have heard about all these difference to be sure. But have you ever _seen_ any?

    Neil
     
  11. benniesdad

    benniesdad TS Member

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    Neil - I told you I was out of my league. I am sure you have thrown out 100 times more patterns than I have ever tested.

    I just recently decided to try to develop a decent 7/8 oz load. I dabbled with this in the past but never tried it seriously until recently. The particular loads using Red Dot and the DR XXL and WAA12L wads seemed to improve (more uniform with less of a hot core) with more velocity. I will plead guilty up front and tell you that this is not based on lots of patterns.

    I may be wandering off topic, but that is why I was asking to see if variations in choke constriction would make these results different thus reinforcing or debunking the conventional wisdom quoted by many to use a tighter choke with lighter loads.
     
  12. Neil Winston

    Neil Winston Well-Known Member

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    Above is what I found with light loads, BD. Again, not enough difference to ever tell anything unless you count the pellets.

    Well, one thing. The patterns are not more uniform as you reduce pellet count, they are less uniform, but in fairness, you can't see stuff like that either.

    Neil
     
  13. twcpdc

    twcpdc Member

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    Thanks for the information I must say I am a little surprised at the results. What does the bottom number of the graph stand for number of shot something to do with distance. Need some info on that number
    Thanks Tom
     
  14. Dr A C Jones

    Dr A C Jones Member

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    This is the graph I was referring to when responding to timb99:

    [​IMG]

    It shows the results from some early tests to identify the best choke for further comparisons. For most of the later tests I used the 39/1000" constriction because from the available data it was the one most likely to give the tightest patterns.


    The graph simply shows the pattern efficiencies. An important point (not shown here) is that the pattern qualities, that is the distribution of pellets throughout the patterns, were on average similar for all the chokes. The 27/1000" didn't give a more even pattern and the 48/1000" one didn't give a pattern that was degraded in any way, counter to what you often read.


    The next graph shows the effect of payload, again with the three chokes:

    [​IMG]


    In this case, the 48/1000" choke had the edge. But again the differences are small. The effect of payload wrt to pattern spread is also seen to be small. Furthermore, the 36-gram shell's pellets were noticeably poorer quality than the others so its quite possible that another batch pattern a little tighter.


    In summary, in the absence of any patterns tests I'd look for ~40/1000" in a trap gun, and I'd rather be a few thou higher than lower. Unless proven to be able deliver 75%+ pattern efficiencies I'd steer clear of guns with fixed chokes about ~30/1000" (unless prepared to multi-choke it).


    Another observation, the first graph is 30-pattern's worth of data, the second one 90-patterns. Neil's graph shows 30-patterns. That 150-patterns in total. With the tools available that's a getting on for about two man weeks of labour.


    Andrew.
     
  15. Neil Winston

    Neil Winston Well-Known Member

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    Tom, in my graphs I put the results of ten shots in some order, in this, ascending based on the total percentage of pellets in the 30-inch pattern. One based on the center might put the shots themselves in different order. All shots are at the same guns, same day, off the same rest at 40 yards from the target.

    The reason I sort them (and occasionally, as I am doing now, explain why) is that you have to impose some order on them to see what's going on. Here's is a typical test before the data are sorted.

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

    As you see, you can't guess what's going on. Add another gun for comparison and what have you got? Well, you have a sketch of Nessie, but that else have you got?

    Andrew has more data and so has to do even more organization, but for my work, which is usually only 60 or 90 patterns, I think this way provides a nice, memorable snapshot of the data.

    Neil
     
  16. Dr A C Jones

    Dr A C Jones Member

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    Neil, I think it would be a benefit to some people if you explained how to interpret the various features of the ordered graphs . . . I could do it, but it's your data . . .

    Andrew.
     
  17. PerazziBigBore

    PerazziBigBore TS Member

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    Barrels are all different.. The bore.. forcing cones.. choke section.. and how it's derived all mean something.. I have more than 1 Perazzi with .032/.045 chokes.. The barrels are vastly different with 24 gram.. Both tight.. but the .045 is rifle like.. On my Bernardelli hammergun.. I have a .038/.052.. Similar results.. Both excellent patterns..the tighter choke having a smaller/tighter pattern on the pattern board..

    Now.. saying all this.. I have had barrels.. that as they approached .040..the patterns got worse.. Very hot cores..then.. very uncertain side coverage..

    In my days of building chokes for card shooting..There is a "sweet spot" for patterns and choke.. Once you go past it.. things start comming apart..

    It's a science I don't fully understand.. There is some relationship between bore diameter..forcing cones.. length of choke taper.. length of the parallel section.. and it all comes together some kind of way..

    I have 1 barrel.. .028/.038 Both throw a very similar pattern in size.. but the .028 is even thru out.. and the .038 is a very hot core with poor coverage outside the hot spot.. Great for bunker..

    My best answer is it takes more than a bore gauge.. pattern different shells and see what you own.. BTW.. I've never had a bad Perazzi pattern.. just some are vastly better than others..
     
  18. Dr A C Jones

    Dr A C Jones Member

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    PBB, Let me go out on a limb here, and state that my tightest patterns were a smidgeon under 80%(**) PE at 40-yards for a 30-inch circle (10-pattern average) with UK#7.5 shot (US#8) as shown above.


    What's your highest average?


    Andrew.


    (**) if you measure patterns by hand by positioning a 30-inch circle, you get slightly higher PEs than those calculated about the mathematical centre of the pattern (which is my method). Hence, the PEs in the graphs above should be increased by 1.5-2% to compare with manual measurements.
     
  19. Twinbirds

    Twinbirds TS Member

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    hard to believe I made the 27yd line with .026 of choke and 7.5's. might be the reason I never broke higher than a 97. live and learn
     
  20. Dr A C Jones

    Dr A C Jones Member

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    Twinbrds, 97 is higher than you can statistically expect to get. As I recall, at 42 yards the average chance of a pellet breaking strike is something like 95%. To get above this requires shooting the target sooner, perfect pointing, and or a measure of chance. Note that just because 95% is the average chance doesn't exclude higher scores; it's an average not an absolute.


    Andrew.
     
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