Unscientific accuracy testing (ongoing) | SIG Sauer 556 Forum

Unscientific accuracy testing (ongoing)

Discussion in '556 Discussions' started by CGRBB, Jun 8, 2020.

  1. CGRBB

    CGRBB Active Member

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    In an effort to consolidate information, and clean up Bosley's info thread, i am posting results from my ongoing unscientific accuracy testing here, for those who are interested and/or bored. I am going to repost everything from Bosley's thread, and remove it from there. Hopefully it won't be confusing outside the context of the replies in that thread. The following is from Bosley's thread...

    Maybe we ought to forget about speculating where barrels came from, and shoot the ones we have. If folks have relatively easy access to a 100yd shot, we could maybe collect data from our guns, and create a chart displaying the data. Model, barrel markings, 5-shot group size, and any mods that may have a bearing. I know it won’t be perfect, considering everyone’s circumstances will be slightly different, but if the spectrum of accuracy variances is as wide as some say, it won’t really matter. Hell, I have a gun with a transplanted Swiss 551 barrel, and I am fairly certain it is the most inaccurate gun I own.

    As long as it doesn’t rain, I will try and perform this data collection today. Some of it anyway. Optics may be something worth mentioning in the chart. Or, in my case, lack thereof. A difference between groups of maybe and inch could potentially be debated if optics are in play on one gun, and not the other, but that’s an unavoidable situation, considering the informal nature of this scenario. I find that 5-shot groups typically eliminate the opportunity for most debate.

    Alright... this was very un-scientific. But I think there’s something that can be drawn from the comparative analysis, as it reaffirms my previous experiences.
    Distance: 100yd
    Target: 5.5” black circle on white paper
    Position: prone unsupported
    Sights: Swiss diopter (peep; not notch)
    Ammo: 55gr PMC X-TAC
    556 Patrol. Barrel cut by competent gunsmith to 12.5”. No markings on barrel. 8.75” 5-shot group.
    P556. 9.5” barrel. Marked with a capital G. 7.5” 5-shot group.
    551 clone. Swiss 551 barrel in US 556 receiver. 13” barrel. Marked with hammer and rifle images and 0065. 10.75” 5-shot group.
    SAN 551. 13” barrel. Marked with SAN67192 KW 11 2017. 4” 5-shot group.
    I could have predicted the results. I included the clone gun because I think it’s an interesting point. And I figured the SAN gun could act as a sort of “control”. Unfortunately, the two other guns are the only ones I have with US barrels in them right now.

    Welcome back to unscientific shooting with CGRBB. On a whim, I decided to perform the same procedure as before, but with M855. And a rest for the front of the rifle. And I used the notch instead of the peep. So yeah. Like I said: unscientific.
    The notch was unintentional. It’s my default position for the rear sights, and I didn’t think anything of it until I had shot the first group. So I just did it that way with the other guns too.
    The cut-down Patrol shot 4.5”
    The P556 shot 7”
    The 551 barrel in US receiver shot 19”. This is not abnormal for this gun, sadly. It is very typical for it to have 4/5 shots in a relatively normal grouping, but then a flyer that opens it waaaay up. In this case, 4/5 shots were inside 7”, but one of them opened it up to 19”. This is one reason I am such an advocate of 5-shot groups. Smaller groups might miss a freak thing like this gun does.
    The SAN 551 shot 4”
    Upon review of the previous outing, it seems little has changed, other than the group out of the cut-down Patrol. It shrunk by almost half. Is this due to the ammo? Unfortunately, due to the unscientific nature of these experiments, we can’t say. Also, this gun received a gas port adjustment since that previous grouping. So who the heck knows. I wrote up a brief thread in technical discussions on that porting, for anyone interested.

    Alright. You’ve inspired me to unscientifically investigate further, Bosley. I shot four 5-shot groups with the Swiss-barreled 556 today. 100m, M855, diopter peep sight, kneeling-supported, 5.5” black dot on white paper. My wife served as my spotter, and was instructed to keep track of which shot in every group was the flier. Between groups I went to the target and marked all shots, and made special note of the flier.
    *It bears mentioning that my wife has an aversion to loud noises. So she backed away from the shooting position for every shot, and then approached between shots to check the target through the spotting scope. When she did this, I came off the gun. So every shot was more or less a “first shot”.
    All that being said, all the fliers turned out to be the first shot, and impacted to the right of the other shots in the group. Normally that would be shooter-error all day, but considering it doesn’t occur with any other guns, and the circumstances made every shot a “first shot”, I am still puzzled.
    Group1: 5” opened to 20” by flier
    Group2: 4.5” opened to 6.5”
    Group3: 7” opened to 9”
    Group4: 10” with no obvious flier
    So, yeah. Still puzzled.
     
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  2. CGRBB

    CGRBB Active Member

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    Did some more shooting with the same guns today. 100m, M193, kneeling-supported, diopter peep rear sight, 5-shot groups. I also added a Colt 933 to the mix, to have a comparison to the ubiquitous AR platform. All conditions are the same with the AR, and it is a 100% factory LE-surplus gun (11.5" barrel).

    12.5" Patrol - 4"
    P556 - 5.25"
    551 barrel in US receiver - 3.75" opened to 15.75" by the flyer
    SAN 551 - 2.75"
    933 - 4.75"

    Results are consistent with those previously seen. I was quite comfortable in my position today, which led to some slightly tighter groups. Another thing worth mentioning is how nice a fully-hooded front sight is. Not only do you get the obvious advantages of shade and protection from bumps, but it provides a 360-degree reference point for consistent sight pictures. I have also found hooded sights to be much quicker to align in close range snap-shooting as well.
     
  3. CGRBB

    CGRBB Active Member

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    A picture of the guns involved.
    image0.jpeg
     
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  4. Millerdaga

    Millerdaga Member

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  5. Bosley

    Bosley Active Member

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    Yeah, you are as shortie guy. I've got a PDW wire stock for an AR I took off as couldn't stand it. That's about as close to a shortie as I'll get.

    With all these marxists on the march, I won't be doing much shooting as I want to conserve ammo.
    Never can tell.
     

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