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

O/U barrels throw different patterns

Discussion in 'Shooting Related Threads' started by jbmi, Aug 19, 2009.

Thread Status:
Not open for further replies.
  1. jbmi

    jbmi Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    1,451
    I was checking the POI on my two year old XT. Shot at a pattern sheet from 13yds using factory shells out of the same box. I used the same modified choke tube shooting it first in the upper barrel then installing it in the lower barrel and shooting it again. The upper barrel threw a much tighter pattern, maybe 25% , repeated the process and same results. I have not measured the bore dia. of each barrel but is this common?
     
  2. rick979

    rick979 Active Member

    Joined:
    Feb 28, 2009
    Messages:
    1,908
    "Mic" your barrels...they are different.
     
  3. Shooting Coach

    Shooting Coach Well-Known Member

    Joined:
    Sep 14, 2006
    Messages:
    8,351
    Location:
    Nashville Tn
    The barrels are minutely different, even if the same diameter and model. The shells are also different, even if out of the same box.

    My Browning Unsingle is a Martian Death Ray with the Angleport XF choke. The O/U barrels prefer looser chokes. Also, my Browning Special Sporting does not perform well in either barrel with the same choke. All bores are the same .740" diameter, are all factory ported, and are unaltered. All the Angleport chokes have the same skirt diameter, etc.
     
  4. phirel

    phirel TS Member

    Joined:
    Jan 29, 1998
    Messages:
    9,556
    Could be a problem here. Checking the POI at 13 yards is fine, but you get nothing more than the POI at this distance. You get no information about the pattern.

    To compare patterns you need about 10 patterns from each barrel at 40 yards (a little less is OK) then you get to count a lot of holes. You need to compare the mean number of holes in the 20 and 30 inch circle +- 1 SE to see if there is really any difference.

    Pat Ireland
     
  5. Neil Winston

    Neil Winston Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,845
    Pat, I can tell a lot about my patterns at 13 yards if I use 1 1/8 oz. of shot and 7 1/2's of light premium factory shells. I generally use light Winchester AA's for this. 8's work to some extent as well. I use Kraft-weight paper and get these results:

    1. A hole about the size of a quarter = full choked

    2. A lacy hole, one where most of the paper can be fitted back onto what it once was = Improved Modified

    3. No hole = less than IM, for me, a doubtful choice for trap (for me), but every now and then I try it though never for long.

    Of course, to know more you need to do as you said, but the above system has weeded out both unsuitable barrels and unsuitable shells for a long time for me.

    Neil
     
  6. SirMissalott

    SirMissalott Active Member

    Joined:
    Mar 29, 2006
    Messages:
    2,241
    How did or how should the actual POI vary between the top & bottom barrel. jbmi thanks for the post very interesting. Jim W
     
  7. Andy44

    Andy44 Active Member

    Joined:
    Jan 29, 1998
    Messages:
    1,262
    For Sporting Clays & hunting, I like my barrels to shoot 50/50. For Trap Doubles and Bunker, I want my bottom barrel 70/30 and top barrel 50/50.

    AndyH ;-)
     
  8. Shooting Coach

    Shooting Coach Well-Known Member

    Joined:
    Sep 14, 2006
    Messages:
    8,351
    Location:
    Nashville Tn
    Andy hit the nail on the head, several times!
     
  9. phirel

    phirel TS Member

    Joined:
    Jan 29, 1998
    Messages:
    9,556
    Neil- Your system intrigues me but I have questions. If I tried to compare 10 patterns with your system, would not I have to find a nonparametric statistics book or would your system have a potentially normal distribution?

    Pat Ireland
     
  10. Neil Winston

    Neil Winston Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,845
    Pat, as you well know, patterns vary - one to another on consecutive shots - not only in their pellet distributions but also their placement relative to the POA. Close-up patterning gives you enough shots in a reasonable time to end up superior to most other methods no matter what other theories people may hold.

    So close-up patterns vary too. Consider a success/failure test for a full choke, that is, does it drill a hole or not? By using a binomial test, you could say that 8 or more "holes" in ten close-up patterns means your gun really shoots full-choke patterns (P=less then 0.05). Want to know IM or full vs more open? Just call a success a clean hole or a laced one in contrast to a a failure, a more open one. Same test, same result.

    The time savings vs counting holes at 40 yards is hours; the information loss is little or nothing. It's more likely a gain, since who's going to count pellets? Really?

    Neil

    PS. I'm not dead-sure about the appropriateness of the statistics I outlined above, but I _do_ usually get at least eight of ten clean holes and the guns _do_ shoot "full" a great majority of the time.
     
  11. BMC

    BMC Member

    Joined:
    Oct 12, 2006
    Messages:
    769
    jbmi, my XT shoots the same POI as yours. The bottom barrel shoots higher than the top, which I actually perfer for doubles.
     
  12. phirel

    phirel TS Member

    Joined:
    Jan 29, 1998
    Messages:
    9,556
    Neil- I really don't have an argument with your conclusion, but I do have a problem with your analysis. A hole, or no hole only gives two possible results that are not continuous and this would require nonparametric statistical analysis. I am not ready to give up my belief that 13 yards is for POI and 40 yards is for pattern analysis, but you have me thinking.

    Now, watch Larry jump in and tell me I am wrong with my nonparametric thinking.

    Pat Ireland
     
  13. Neil Winston

    Neil Winston Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,845
    OK, Pat, I admit it. I just take the kind of result I get most of the time and leave it at that. My notebook says "full" or "IM" or "mod or less" and that's all I need, just what I see most of the time. Too many - let's say more than two in ten - "mods" where I expect "full" and I know I'm looking at an ammo problem. Sometimes, of course, ammo problems will show themselves in ten of ten and I'm thinking of a particular factory non-premium shell when I write that.

    Still, I can't agree with your idea that two possible results that are not continuous require non-parametric analysis. Don't coin flips fulfill those criteria and aren't they duck soup for binomial treatment?

    Neil
     
  14. Jawhawker

    Jawhawker TS Member

    Joined:
    Jan 29, 1998
    Messages:
    3,734
    Neil, you know who really counts each of those pellets in each and every pattern...

    You also know that different wads will punch through where some may not at 13 yards. It seems to me to be untruthful with results but then again, Iam stubborn...

    What if you could get 5 consistent patterns from one gun/barrel/choke/load combination without enough difference to warrant noticeability?
     
  15. phirel

    phirel TS Member

    Joined:
    Jan 29, 1998
    Messages:
    9,556
    Neil- Good point about the coin flip. Not that I an totally convinced but now I am confused. I did take a non parametric stat class once and I would like to at least once use what I learned. I would hate to think I wasted my time and effort 40 years ago. But, I also took a Psychology class.

    Pat Ireland
     
  16. Neil Winston

    Neil Winston Well-Known Member

    Joined:
    Jan 29, 1998
    Messages:
    7,845
    Pheasantmaster, it's true that the wad will make its own hole at 13 yards, but that's not the kind of hole I'm talking abour.

    Here's a typical wad hole:

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

    There could be a wad hole concealed in this full-choke one but usually it shows up somewhere else on the paper:

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

    And here's a laced hole I attribute to an improved modified choke:

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

    and I don't think a wad could have gotten through there.

    And yes, I know you do count holes; I meant anyone _else_.

    Pat, according to Sidney Siegel in his book of the same name, nonparametric statistics are used:

    1. When the normal distributions other statistics depend on are not there and

    2. When the data are rank orders or classifications (for example) or other non-numerical forms.

    Neil
     
  17. phirel

    phirel TS Member

    Joined:
    Jan 29, 1998
    Messages:
    9,556
    Neil- A sort of round hole-- A kinda round hole with floppy edges and no hole sounds like a non numeric ranked order to me. I have though more about your system. I am about convinced that it is a quick and reasonably accurate way to check the choke in a gun. I also believe is would be a very poor way to compare the patterns of magnum, chilled and reclaimed shot.

    I do confess to counting a lot of holes over many years. I have learned relatively little for the effort I put into the work.

    Pat Ireland
     
Thread Status:
Not open for further replies.