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300 yards ... a true 1/4 MOA rifle and load ... 15 shot group in 0.814 MOA.

Discussion in 'Rifle Country' started by MCMXI, Oct 25, 2010.

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  1. MCMXI

    MCMXI Member

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    300 yards ... 15 shot group in 0.814 MOA ... a true 1/4 MOA rifle and load perhaps?

    This post isn't an attempt to show off but rather an effort to show what can almost happen when everything comes together during a match. I'd also like to start a discussion on what it means to have a TRUE 1/4 or 1/2 MOA rifle and load. I scored a personal best yesterday at 300 yards with 15 shots in 15 minutes plus two sighters. My rifle is zeroed for 200 yards so I dialed in +0.7 mils of elevation and -0.3 mils of windage and held on center. The first sighter S1 just clipped the X-ring. I made no adjustment for the second sighter, held on center and a wind gust pushed the bullet to the right. Luckily, I realized that the wind had picked up so I made no adjustments for the next 15 rounds but held off to the left slightly and tried to time my shots with the wind. My score was 149-4X with one 9 which was the 14th shot! The scorer told me that the wind suddenly dropped right as I pulled the trigger ... :banghead: I shoot F-TR which means a bipod and some form of rear bag. The conditions were tough with the sun right in our faces and wind gusting from 5mph to 12mph. The wind proved to be a bigger problem at the 500 and 600 yard lines where we had 15mph to 20mph gusts. My overall score was 435-8X (master).

    So why do I say a "true" 1/4 MOA rifle and load. Well, I don't believe that you can shoot a 15-shot 1/2 MOA group with a 1/2 MOA rifle and load. Statistically it just isn't going to happen. If you have everything optimized, the vertical deviation is a true indication of your system because wind will mostly affect the bullet left to right rather than up and down. The 15-shot group for score shown below has a vertical deviation of 0.548 MOA. Both sighters (S1 and S2) are inside that vertical spread. Given aiming error and variations in each round, the rifle would have to be capable of considerably better than 1/2 MOA, something more like 1/4 MOA.

    Needless to say, I'm very pleased with the target below and doubt that I'll repeat that performance anytime soon.

    [​IMG]

    [​IMG]

    Here's my string for the 300 yard stage.

    S1: X
    S2: 9
    #1: 10
    #2: 10
    #3: 10
    #4: 10
    #5: 10
    #6: X
    #7: X
    #8: 10
    #9: X
    #10: X
    #11: 10
    #12: 10
    #13: 10
    #14: 9
    #15: 10

    :)
     
    Last edited: Oct 27, 2010
  2. desidog

    desidog Member

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    Nice shooting. So what's this boomstick look like? No rock-lock, i take it?
     
  3. TonyAngel

    TonyAngel Member

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    FWIW, I agree with you 100%. I don't get the opportunity to shoot past 100 yards very often, so most of my experience is shooting at 100 yards. I just try to make the most of it by shooting at really small targets.

    I have shot some pretty good groups, relative to the way that I was shooting a year ago. I can't say that I have "just" a sub MOA rifle, because that would assume that I did everything perfectly every time I pulled the trigger, and I know that is impossible. I would imagine that if I'm able to pull off sub MOA groups, that the rifle is capable of shooting twice as good as the groups I am shooting, if you took me out of the equation.

    I can live with this since I build my own rifles and get a sense of self satisfaction knowing that my rifle can shoot better than I can.
     
  4. SSN Vet

    SSN Vet Member

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    very impressive!

    What's ATC stand for?
     
  5. FlyinBryan

    FlyinBryan Member

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    very nice (although not terribly suprising coming from you, lol)

    i clearly remember being impressed with your work when you competed in one of my ar-15 matches not long ago.

    load info?
     
  6. Dave P

    Dave P Member

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    OK - I am confused.

    "... a true 1/4 MOA rifle and load .."



    Your max spread is 2.55", which is about .8 MOA (like the software says). A 1/4 MOA group would be about .75".
     
  7. MCMXI

    MCMXI Member

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    The max spread in the horizontal direction is due in part to wind so this is NOT an indication of the rifle/loads potential accuracy. The max spread in the vertical direction is a better indicator of the rifle/loads potential. There is still error, both load and shooter induced in the vertical direction. If you have a rifle/load truly capable of 1/4 MOA grouping, not just for 3 or 5-shot groups but for 10, 15 or 20-shot groups with 1 minute per shot, it's highly unlikely that you'll shoot 1/4 MOA groups. Think of the variables such as the SD of the load, shooters ability to hold on target, wind, parallax etc. In fact, I'll go so far as to say that you need a 1/4 MOA rifle/load to even have a chance of shooting a 1/2 MOA group. Another thing is that S1 was the first shot out of that rifle and #15 was the last over an allotted time of 17 minutes. In fact, I finished in under 15 minutes. There is no significant difference in the POI as the barrel fouls and heats up. Another indicator that this is an excellent rifle.


    Average distance to center of the group. The software calculates the center of the group (centroid if you like) which I find useful since I use that average group center to check my scope adjustments. The Off V: value tells me how low or high the average group center is compared to the point of aim on the target. In this example, the group center is less than 1/2" low at 0.436". With 0.1 mil adjustments, if I come up 0.1 mil, that would move the group center 1.08" up which would put me over 1/2" high. Basically, the comeup of 0.7 mil is as good as it gets at 300 yards. If the scope had 0.05 mil ajustments I would make a change but 0.1 mil is as fine as it gets.



    Thanks ... here's the load info ...

    178gr A-MAX
    CCI 200 primer
    44.2gr of Reloder 15
    Lapua brass fired three times



    Sort of like the photo below but with a Premier Reticles Heritage 3-15x50mm scope on it. I'm very pleased with the Seekins rings that I have on the PRH. A few months ago I took the PRH off after using it for a course and some F-Class matches. I wanted to try the Mark 4 again so I removed the PRH with the Seekins rings still on the scope. A couple of weeks ago I put the PRH back on and didn't even check the zero before yesterday's match. First shot (sighter) at 300 yards was an X ... now that's my idea of a repeatable zero after removal and re-installation!!

    [​IMG]

    :)
     
    Last edited: Oct 25, 2010
  8. JDGray

    JDGray Member

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    Great shooting!! And I'm happy with 5 shot groups that size:D
     
  9. USP45T

    USP45T Member

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    is that a 1.5" x-ring? nice of your scorer to give you an X for S1. I wish they'd score me like that where I shoot. There's usually money involved. lol
     
  10. MCMXI

    MCMXI Member

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    JDGray, thanks ...

    Actually, the X-ring is 1.40" and the 10-ring is 2.85" in diameter. S1 clearly breaks the X-ring but it doesn't help since S1 and S2 don't count for score. At the 500 yard line, S1 and S2 were both 10s, but my first shot for record was a 9!! :banghead:

    You have to shoot either .223 Rem (5.56x45mm NATO) or .308 Win (7.62x51mm NATO) in the F-TR class, but I don't know anyone that is competitive that shoots .223 Rem. The bullet diameter would put you at a disadvantage in terms of breaking the X-ring or 10-ring, not to mention wind drift at 300, 500 or 600 yards.

    :)
     
  11. Walkalong

    Walkalong Moderator

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    Great shooting, but what is the distance center to center of the two furthest shots? That is the group size, and it would have to be .75 or less to be 1/4 MOA.
     
  12. Dr T

    Dr T Member

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    Very, very impressive shooting.

    As a probabilist, I must agree with you. I am not sure what the term would mean mathematically. If you assume that your shot placement has a two dimensional Gaussian distribution, by saying that a rifle is a true 1/2" MOA, does this mean that 95% of the shots would land in a circle of radius 0.25"?

    The calculations can get complicated (see http://en.wikipedia.org/wiki/Multivariate_normal_distribution).

    Perhaps it would be better to use the CEP (circular error probable) like is used for targeting heavy ordinance (see http://home.earthlink.net/~loganscott53/Circular_Error_Probable.htm )

    Personally, I prefer to reduce things to a univariate case. I look at the axis of extreme spread that you have highlighted. What ever that distance is, I call it the group size.
     
    Last edited: Oct 25, 2010
  13. USP45T

    USP45T Member

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    Thanks for the info. I guess I don't see too clearly. Nice shooting. A 1/4 moa rifle is a joy to shoot.
     
  14. wanderinwalker

    wanderinwalker Member

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    Nice shooting! Mid-range prone shooting is hard enough, those F-class targets are just diabolical. Must have been drawn up by some kind of sadist. "They want to shoot scopes? Then check THIS out!" :eek:
     
  15. taliv

    taliv Moderator

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    Nice shooting!

    I take it you don't have pit service and paste targets between shots? Your scorer determines the value from behind the line?
     
  16. Uncle Mike

    Uncle Mike Member

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    Nice, Nice, Nice!
     
  17. MCMXI

    MCMXI Member

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    Walkalong, I'm not claiming that the group is 1/4 MOA ... clearly it is not. What I'm saying is that given the 0.5 MOA of vertical spread for 17 shots which is largely independent of wind, and given the human and load error, the rifle and load together would have to be a lot better than 1/2 MOA.

    Dr T, thanks for the links. I need to read up on the statistical part and figure out how to sum all of the errors inherent to the system to make sense of this.

    :)
     
  18. MCMXI

    MCMXI Member

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    We do have pit service and we take turns pulling the targets. We typically have three relays, one shooting, one scoring and one pulling targets. We use pasties but they're of low quality and are easy to remove after the match when we get our targets back. We tape up a new face center for each shooter over the correct high power target.

    :)
     
    Last edited: Oct 25, 2010
  19. taliv

    taliv Moderator

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    cool. We do the same, but when i put the spotter in the hole it usually makes the paper tear slightly different and our pasters hold pretty well except in august when my hands are sweaty
     
  20. MCMXI

    MCMXI Member

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    We use golf tees with a 1" rubber washer painted white on one side at 300 yards. We use a regular 3" spotter at 500 and 600 yards. The 1/2" small round pasties are junk but the 3/4" larger square ones are very good. I cut them in half when I'm pulling the target so that I don't obscure the rings. I was just looking at the national records for 300 yards (15 shots). The open and civilian record is 150-7X. Nancy Tompkins holds the women's record with a 149-5X. I was 1X behind her and given that she's a phenomenal shooter I feel good about that. The national record for the mid range prone course is 442-27X! :what: I have a long, long way to go with my best so far being a 435-8X.

    :)
     
  21. 52grain

    52grain Member

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    I think both the univariate and the bivariate treatments. The math isn't that bad. If I didn't have other things to work on, I'd make a Matlab routine to handle it.
     
  22. Walkalong

    Walkalong Moderator

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    In that case, every group I have shot with my bench gun would be a zero, cause the rifle is capable. :D

    Seriously though, that's good shooting. My last 300 yard group (I shot one with an unknown load the other day and haven't shot at 300 in years) was double yours. I loaded two more loads to try in the .222 Mag. I am going to try it at 100 & 300 one of these days. I am almost out of the Hornady bullets that this gun will shoot 1/4" groups with (if (big if) I do my part), but Hornady changed the bullet. I am trying some 52 Gr A Max bullets to see if I can find a combo they like in this rifle. The 50 Gr V Max is next. Even with a rifle and load that is capable of shooting 1/4 MOA, it is difficult to actually do. I would be most happy to shoot a group like the one posted using a factory rifle.

    You are right. The rifle/load must be able to shoot much better than that group, to be able to shoot that group, given human error, wind etc. We only wish we could shoot to our rifles potential. Well, sometimes we do. :)
     
  23. MCMXI

    MCMXI Member

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    Exactly!!!

    :)
     
  24. p5200

    p5200 Member

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    Great shooting and a very sharp looking rifle! :)
     
  25. TexasPatriot.308

    TexasPatriot.308 Member

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    money, money, money.....
     
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