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Pattern testing

Discussion in 'Shooting Related Threads' started by mercedesman1981, Jan 27, 2008.

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  1. mercedesman1981

    mercedesman1981 TS Member

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    I got to the stage where I need to do some pattern testing. Handicap competition is a good driver to get the most out of your gun and loads.

    I found my MEC 1oz charge bar really drops about 26grams. I picked up an adjustable bar and bumped up the charge to a full ounce and headed to the patterning board.

    I was surprised to see a fuller pattern with the 1oz load. I also learned I have about a 70/30 pattern, printing about 4" high from aimpoint (at least that was where I drew my 30" circle and over the course of several targets, found an 80% hits within the circle).

    One question is this, is 80% - 82% a good number at about 37yds for a full choke?

    I also noticed my patterns were noticibly a bit to the left of center. I don't know what would cause that, I'm shooting a Browning XT Over/Under with Briley Stainless Choke tubes and using the upper barrel. My thought is canting should be a minimum from the upper tube. The other culprit might be a rib mounted sight-blocker which may be skewing my bead relationship.

    If anyone can help me to interpret the results, I would be glad to upload pictures of the patterns I shot.

    Thanks for taking the time to read/respond.

    Mike
     
  2. Neil Winston

    Neil Winston Well-Known Member

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    Eighty percent is just OK from 37 yards. It could be better, especially if you are shooting from long yardage, but call it passable for now. Was this name-brand magnum shot and did you count the number of pellets in a couple of example shells?

    The left shooting is not certain unless:

    1. It is confirmed off a bench at 13 yards

    2. There was no wind at all, even a breeze you can hardly feel.

    I found interesting your observation that adding a couple of grams of shot improved the visual impression of the patterns. At Tucson I plan to pattern 7/8 oz. loads and hope to be able to see if that impression is carried forward to actual probabilities of single.pellet hits.

    Keep up the good work - and as you see, it _is_ work.

    Neil
     
  3. mercedesman1981

    mercedesman1981 TS Member

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    Thank you for the replies.

    Neil, For the number of pellets, I used a 4'X4' piece of paper and counted all of the hits on paper, then used that for my total to calculate the percentage within the 30" circle. I take your point in that there may have been a few that didn't even make the paper. The total number of pellets seemed to coincide with the weight of the charges thrown, plus or minus a few. I'm using #8 shot which weigh about 1.1 grains per pellet. I could count out the pellets before testing again if you think that would make for a better sample rate.

    I am using brand name magnum shot (I think it is called Northwest - I'll have to check when I get home, I believe the bag says it is hardened or Magnum shot).

    If there was a breeze, it was imperceptible. The target paper was only anchored at the top and very sensitive to any air movement, the paper remained still for the testing.

    Previously, at an indoor pistol range, I wrote here I did some bench testing with this gun and its accompanied Browning choke tubes (Inv+). You and zzt were quite helpful with analyzing my results. With the Browning chokes, I found the bottom barrel was shooting to the left by about 1.5" at 13yds, the top barrel was centered, both hitting the paper at about 1.5 to 2 inches high which doesn't quite square with my pattern testing at 4". There may be two factors at play here. One is the comb. This gun has the adjustable comb and it has been adjusted since the POI testing. I found the locking mechanism in the stock tends to allow the comb to move even when the lock-screw is tight. I reset it and installed spacers to help keep it from moving.
    The next problem may have been the sight blocker. It was rib mounted on the left side (left eye dominant), and caused sensory confusion as to where the beads were actually lined up, ie, was I able to get the beads lined up straight? Since there was doubt here, I removed the sight blocker and will re-test. Just mounting the gun at home I perceive it to be much easier to line up the beads without doubt or hesitation. I think zzt hit the right solution for a sight blocker for left-eye dominant people by using a "hooded" fiber optic tube.

    From my previous round of POI testing, I found I canted the gun a bit to the left so the under barrel shot to the left while the over barrel was centered. I confirmed this with the use of a level. I'm curious though and will retest it (with the level) but will also test with Briley chokes.

    Kelley,
    I was careful to squeeze the trigger and not jerk/slap it. I also used a "bench rest", actually the hood of my car which was wet but stable. I have shot a lot of bullseye pistol and competed in the Northwest so I'm acquainted with those problems. I appreciate your input too regarding the choke/pattern and yardage. I'm currently D-class shooter on the 20yd line, During this testing period I tested my Invector + Improved Modified choke (which I had been using for this years winter league handicap) and found at 37yds, the pattern is quite wide open. I kept the target, I just didn't score it yet because I got tired scoring 5 others. I am curious how it did percentage wise and will get to it eventually (I will guess about 60%). It was certainly interesting to see this as my results thus far in this years league has been dismal, scoring in the teens with a low of 11. At the last meet, I turned in 3 scores of 20 and a 21 using my Briley full choke. I hope that trend continues and it wasn't just a good day.

    As for the 80% results, I wonder if it could be the wads? I'm using Downrange equivalent AA12SL's (bright green). I know zzt had good success with Federal 12SO's, but can't find any locally to test with. I also have some Downrange TGT12 clones I want to try. I should probably try factory loads too.

    It is a lot of work, but its paying attention to details like this which is the only path to the winner's circle.

    Your thoughts/comments are deeply appreciated.

    Mike
     
  4. JBrooks

    JBrooks TS Member

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    Neil,

    What is the pattern drift at 40 yards with say a 10 mph crosswind? Is there measurable, material difference between 7.5s and 8s? Does initial velocity make much difference?

    JT
     
  5. coffee

    coffee Member

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    Mercedesman...Everything else aside I watched Phil Kiner's latest video and he said (right handed shooters)may shoot to the left when raising the comb! Good Luck.........COFFEE
     
  6. zzt

    zzt Well-Known Member

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    Mike, congratulations on the hard work you are doing. I have a couple questions about your methods. You say you drew a circle, presumably 30" diameter, an averaged 80% pellets hits inside the circle at 37 yards. You also say the center of your pattern hit 4" high. Where did you aim? If you aimed at a mark in the center of the circle, your whole pattern is shifted up by 4" and you would end up with more pellets in the higher circle. If you know your gun shoots 4" high at 37 yards, Put your aiming mark 4" below the center of the circle you drew. Then aim at your mark and fire. That will center the pattern in the circle and give you the most accurate results. If you want to make life easier, just adjust your comb so you shoot dead on at 37 yards. Now you are zeroed, and you can record the number of spacers under your comb. That is your base pack of spacers. You will never use less than that amount. You also can now just aim at the dot in the center of the circle and not have to worry about offsets.

    I have forgotten which hull you reload. In any event, I wouldn't worry too much about wads right now. If you are using STS or Gun Club hulls, use STS209 or W209 primers, your favorite powder and TGT-12 wads for 1oz and Fig-8 wads for 1 1/8oz. You know they are going to work. I haven't patterned the DRM replacements yet, but I'm sure they are OK.

    When I was doing a lot of patterning, I would save a bag of particularly round, consistent shot for just that purpose. I weighed and counted a bunch of samples and found that I was never off by more than 1 pellet. That is plenty accurate enough. So I just weighed the shot charges for a boat load of shells and saved them for patterning.

    I think your choice of shot will make more of a difference than the wads you use (within reason).

    Are your Briley chokes flush, or extended?
     
  7. mercedesman1981

    mercedesman1981 TS Member

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    Thanks so much for the replies!

    Coffee - thanks for the tip! I will need to get Kiner's video, I need lots of help on the 20!

    zzt - Thank you for your insights. I have the DRM clones of the TGT-12's so will try them on my next patterning session.
    Load: STS green hull, DRM AA12SL wads, 1oz magnum shot, 18grs Clays, W209 primers.

    I marked a large "dot" in the center of the paper for my aim point. Then looking at the pattern of pellets, pattern density appeared to be about 4" high. In all of the targets I counted, I measured 4" above the center of the aim point to draw the circle. After the circle was drawn (centered on the paper), one can see where the pattern and density was shifted (to the left).

    When I get home from work I will try to attach a picture to my next post. Also when counting pellet holes, the higher density counts were in the left hemisphere on all targets.

    Regarding the use of spacers on the posts for the comb, I really like your thoughts along this line.

    As a note, If I had a 30" circle made of plexiglass or some other semi-rigid ring, I could move it around on the paper to come up with the highest density and perhaps a better percentage, but I don't think it would be more than a couple of points. That is just a guess, I'm also a novice to pattern testing. I recall Neil's words about doing this enough times to get a feel for what is going on and he is absolutely correct. I think it impossible to take a single shot at a piece of paper and have a clear idea of performance.

    The Briley chokes are the Extended version, bright Stainless Steel. I don't know if Briley chokes perform differently from one version or the other, though I would think if all models are well made it should not make any difference. The Browning chokes were the standard issue flush chokes that came with the gun.

    All good thoughts here, thank you for the insights.

    Mike
     
  8. nipper

    nipper TS Member

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    The only problem issue i see is northwest "magnum" is reclaimed shot and of thr 4 bags i have opened it dosent take a micrometer to see different sizes but i am loading it at 1 oz. and it works great.

    Bill
     
  9. hmb

    hmb Well-Known Member

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    After extensive testing I have found that shells loaded with equal amounts of different sized shot have on average 6.73% denser patterns at 36 yards. The best patterns were from equal amounts of 7 1/2s and 8 1/2s. HMB
     
  10. willing

    willing Member

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    Mike= The Browning flush IM is equivalent to a Briley Mod, ie .020.

    Bill
     
  11. mercedesman1981

    mercedesman1981 TS Member

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    Just got home from work, I'll start on the photographs in a bit.

    The shot I'm using is West Coast Premium, Magnum shot - Extra Hard Shot, from Carson City, Nevada.

    Bill, thanks for the tip. Do you know if Browning's flush Invector Plus Full is also more open than a Briley Extended Full? Time isn't of the essence here so I can research that answer later, just curious right now.

    Thanks for the input,

    Mike
     
  12. Jim101

    Jim101 Active Member

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    JB, I don't have my book handy, But I believe the shot drift is about 8-9 inches at 40 yds in a 10 mph cross wind. Not a lot of difference between 7 1/2s and 8s.



    Jim
     
  13. Neil Winston

    Neil Winston Well-Known Member

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    Jim, that's what Ed Lowry's program, Shotshell Ballistics for Windows, says as well.

    Neil
     
  14. otnot

    otnot Active Member

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    If you want to post multiple pictures in one post. Copy and paste the HTML code from photobucket and paste it in this message box seperated by a double space.

    Jim
     
  15. zzt

    zzt Well-Known Member

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    Well, judging by the picture on PhotoBucket, I'd say you are considerably to the left, more than a couple inches. Try the same choke in the other barrel and see if the POI is the same.

    Otherwise, it looks like a pretty good pattern. I've seen many that were much worse. When you try it again with the TGT-12 or the DRM clone instead of the WAA12SL clone, you may find you have a more evenly dispersed pattern, but you might be 1% or maybe even 2% less dense.

    You need to confirm weather the sight blocker caused the shots to go left, or there is another reason.

    Rather than draw a big, clay target sized blob as an aiming marker, I use the fluorescent orange dots I buy in Staples. They are self adhesive, about 3/4" in diameter, and are quite easy to see at any distance. I find it helps with aiming when patterning. BTW, I'm not as keen as Neil is about having Shotgun Insight determine the pattern center for me. One errant flier and it will report a center 2" off. When I am seriously patterning, I set up on a bench with a rest. The barrel is supported, the stock is supported, and the gun just isn't going to move as I squeeze the trigger. Since there are no fliers, I call my aiming point (or offset if I don't have an adjustable comb) the center of the pattern, regardless of what SI says it is.
     
  16. mercedesman1981

    mercedesman1981 TS Member

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    Thank you for the comments ZZT. I removed the sight blocker and am interested in testing again which won't occur until this Saturday. I want to head over to the pistol range to POI test to see if I am re-aligned. I sure hope so. I was quite taken aback by the consistent left sidedness of all the patterns.

    I'll try another photo for this entry, it is one of the 26gm patterns.

    Mike
     
  17. mercedesman1981

    mercedesman1981 TS Member

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    here is the other 26gm load...
     
  18. Neil Winston

    Neil Winston Well-Known Member

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    Once again, zzt, you've left me scratching my head wondering from where you come up with some of these ideas of yours. Last week it was "percent high;" this week it's your complete misunderstanding of how the program Shotgun-insight works.

    You wrote, above,

    "BTW, I'm not as keen as Neil is about having Shotgun Insight determine the pattern center for me. One errant flier and it will report a center 2" off."

    Now I don't know why you think that happens, or in fact how it could happen, but your assertion is totally wrong.

    Here's a randomly-selected pattern - not a particularly good one, but that's the way random works, isn't it?

    [​IMG]

    I've moved the aimpoint around a bit to get the offset very small, and as you read in the lower left corner, it's 0.02 inches for the Y coordinate, the vertical one. The one we will keep track of as we add errant pellets.

    Now here I've added the single pellet you specify, about 18 inches below the aim-point, marked in orange for ease of identification.

    [​IMG]

    As you see, the calculated POI has not moved so much as a hundredth of an inch, a far cry from the kind of change you predicted.

    Of course, maybe the program just doesn't work at all - we need proof that you _can_ move the POI the way your expect. So here I've added _ten_ pellets way at the edge of the paper, again marked in red.

    [​IMG]

    And here the POI has moved. Ten errant pellets, all clustered right at the edge of the paper, have moved the POI about two-tenths of an inch.

    In other words, Shotgun-insight handles errant pellets about as you would expect a proper program to do, and not at all in the way you erroneously describe.

    Neil
     
  19. Hap MecTweaks

    Hap MecTweaks Well-Known Member

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    mercedesman1981, a botched forcing cone job will look real close to your pattern posted above also. I know first hand how it affects one side or other of the pattern, mine was weak on the left side. Re-cut with a new cone reamer and polished, the gun shot patterns centered as it should then. Might want to check that out also. Hap
     
  20. mercedesman1981

    mercedesman1981 TS Member

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    Thanks for the tip Hap. The photo's of my POI testing tonight may be of interest, I don't know. I shot 5 targets and they were all closely centered.

    http://i198.photobucket.com/albums/aa271/mercedesman1981/DSCN1092.jpg

    I don't know if this one will come through, but both the over and under barrels seemed to be centered at 13yds.

    Mike
     
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