The Firearm Thread (Best 50 yard group)

Discussion in 'User Topics' started by djfly, Sep 6, 2016.

  1. djfly

    djfly Smiter of Spam

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    Lost focus on a pair, one got way high (off the paper) and one way low.
    Other than that, trigger-pulled a couple to the right, but the group is fairly solid.

    50 yards
    10 rounds (5 + manual reload + 5)
    65 seconds total
    7.62x39mm (SKS)
    Wood stock / Iron sights

    14199680_163447387392774_7894164820257679681_n.jpg

    (Outer circle is 7.5", next is 4.5", black is 1.5")
     
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    Last edited: Sep 6, 2016
  2. skullpirate01

    skullpirate01 Guest

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    One of em almost dead on center, nice shooting especially with ironsights.
     
  3. djfly

    djfly Smiter of Spam

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    The rifle was hitting about 6" high, I needed to add 1/8" to the front sight-post, but I didn't have my sight adjustment tool with me.
     
  4. skullpirate01

    skullpirate01 Guest

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    Oh so if the sight hadn't of been so high those first shots would have been on target, right on. Ironsights = dopeness :D
     
  5. Cib3rNaut

    Cib3rNaut Guest

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    I been thinking a ton about using tele-metrics and cybernetic audio gear to try and hit targets at hugely ridiculous distances like over 1KM with standard army rifles and scopes. Seems plausible if the target wasn't moving and wind was very low.
     
  6. djfly

    djfly Smiter of Spam

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    1. Real life snipers are already hitting targets out past 2km, the current record holder close to 2.5km.
    2. Big (perm-mounted) guns already use telemetry to hit their targets (see the guns on battleships)

    Ignoring gravity, rotation of the earth, wind, moving target, etc., the biggest problem is air resistance. Even with modern (spitzer, boat-tail) bullets, friction with the air slows the round down. In order to increase range and accuracy, you must increase velocity and reduce drag. Even the .50 Browning round would likely hit its limit before 3km.

    Rough numbers:
    Round: .50 BMG
    Distance: 3000 metres
    Flight time: 10 seconds
    Bullet drop: 400 metres
    Earth rotation: 0.04225 degrees (2 metres @ a distance of 3000 metres)

    Assuming a quasi-vacuum, the solution isn't a difficult calculation, for a human or for software.

    The real problem arises when you attempt to factor in varying wind and air pressures throughout the range of the shot. In order to teach a computer to calculate the solution, you'd need to have accurate wind, pressure, and humidity data for every "zone" the bullet passed through. This information would be exceptionally difficult on acquire on a battlefield. A sniper team can reduce this massive amount of data to a judgement call. Short of moving to a much larger gun capable of much higher velocities (and thus distance and accuracy), I doubt telemetry would ever help with standard sniper rifles. Humans are already taking the weapon systems to their limit.

    Notes:

    1. Before anyone argues, though the shooter and target are rotating with the Earth, the rotation of the Earth matters because the bullet is in the air, and the air is not coupled to the Earth's surface, so in essence the earth is spinning under the bullet)

    2. As another aside, I can 16" targets at 200 metres with that same rifle with iron sights, that's accurate enough for a hit on the battlefield. A well practiced shooter with a mid-sized hunting round, 7.62x51 NATO, 7.62x54R, or 30-06 Springfield for example, with good optics, should be hitting (deer) vitals out to 400 metres without too much issue. Plus, plenty of recreational (benchrest) shooters shoot to distances far past hunting distances using a wide variety of hardware.
     
  7. skullpirate01

    skullpirate01 Guest

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    Dude even 3 kilometers isn't enough for the Earth's rotation to come in as a variable, maybe at 5+km the curvature of the Earth might start to come into play but really the Earth is pretty flat and the rotation is too huge a factor not coming into play because the time the bullet is in the air won't be enough either to affect it being a hit or not.
     
  8. skullpirate01

    skullpirate01 Guest

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    Reminds me though I need to practice my distance shooting next time I get the chance, we were just shooting at 100m with a scoped Remington. No challenge at all even with only ironsights....
     
  9. djfly

    djfly Smiter of Spam

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    Wrong. This is a VERY REAL problem when talking about long bullet transit times. Want the math?

    Let:
    There be no gravity
    Us exist in a vacuum
    The bullet leaves the muzzle at 3500fps (high powered rifle)

    Thanks to the previous assumptions, the bullet does not slow down

    3500fps = 1066m/s
    3000m @ 1066m/s = 2.8s

    In reality, because the round gets fired 400m over target, it actually travels closer to 4000m to hit a target at 3000m, and the bullet loses the majority of its velocity, the transit time is closer to 10 seconds than 3... but, I'll demonstrate the appoximate math with "3 seconds"

    There is one rotation of the earth per day, 360 degrees in one rotation, 60 minutes per degree
    There are 72,000 seconds in one day
    There is one rotation per day.

    Thus, every second that elapses, the earth rotates .005 degrees. in 3 seconds, .015 degrees, aka almost 1 minute of angle.

    So, how far is 1MOA at 3000metres knowing that it's approximately ~25mm at 100 metres, and thus ~750mm at 3000 metres.

    -------

    But don't forget, 10 seconds not 3.
    10 seconds is .05 degrees, or 3 minutes of angle.
    3 minutes is ~80mm at 100 metres, or 2400mm at 3000 metres.

    (1 MOA = 1.047197580733" at 100 yards)

    Edit: I Googled, both the .50 Browning and .338 Lapua magnum rounds have muzzle velocities around 3000fps, not 3500. Because of this, the "flight without gravity or air resistance" will take a bit longer. The math for 10 seconds is accurate "real world" performance as a .50bmg round will take approximately that long to travel 3km.

    I should also point out that this problem is variable and depends on the direction of the shot. The math above assumes a shot that runs on a line connecting the poles, perpendicular to the rotation of the Earth. If the shot is parallel to the rotation, the subject gets 10 seconds closer/further depending on whether the shot is from the East or West, meaning the bullet will travel slightly less or slightly more distance than what the rangefinder would have indicated. This creates an elevation problem instead. I've never had to do the math while shooting, I don't shoot at such distances. Snipers however do need to compensate for this reality.
     
    Last edited: Sep 8, 2016
  10. Cib3rNaut

    Cib3rNaut Guest

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    For every direction your firing the setup the math would change given the exact movement of the earth in coordination to the linear line the weapon would be fired in
     
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  11. djfly

    djfly Smiter of Spam

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    100% correct.
     
  12. Cib3rNaut

    Cib3rNaut Guest

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    Basically if you could rotate space around the gun being fired in a computerized cipher that understood the finalized location of the hit with all physics being taken into account, how far would you predict a higher end weapon could be fired. I'd say 4-6 KM, given the quality of the weapon itself and the shooter using a mounting system that allowed the weapon not to move large amounts while being stationary. Not saying the bullet would be deadly at that range although would it be able to travel fully and meet the intended target right on mark.
     
  13. djfly

    djfly Smiter of Spam

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    What about every single gust of wind that happens between the endpoints? changing air density?

    The current record kill is about 2500m.
    I'm not sure the 50 BMG would be effective past 3500m.

    I'm not sure that every weather satelite combined could calculate an instantaneous solution.

    Typically what happens is that the spotter ranges the target and providers the sniper with a solution.
    Sniper dopes the scope and takes the shot.
    Spotter observes the (missed) shot and makes adjustments to the solution.
    The spotter always gets to see the net result of a calculation when his/her partner takes the test shot.
    He/she can draw conclusions about the atmosphere between them and the target that cannot be seen.

    Software doesn't get this luxury, it would need to predict the output, that IS the problem you're attempting to solve.
    How do you propose that the targeting software acquire all of this telemetry?
     
  14. Cib3rNaut

    Cib3rNaut Guest

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    So it's possible just not probable. I'd say a direct simulation of exact possibles and the timing of flight, leaving only one variable which would be the exact coordinates to fire the weapon to defeat all atmospheric impedance in reaching the target itself, including predictions on every changing pattern in the air before it takes place. Most likely need some kind of radar assist to atmospherically see all possible eddies in the air itself.
     
  15. djfly

    djfly Smiter of Spam

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    That would be my opinion. Possible, but cost prohibitive due to complexity.

    OR, use a really big gun (like cannons on battle ships)
    OR, guide the projectile in flight (missles)
     
  16. Cib3rNaut

    Cib3rNaut Guest

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    Yeah, would be elite to see a person hand firing the weapon though. As opposed to automated systems
     
  17. djfly

    djfly Smiter of Spam

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    Then get into long range shooting! There are plenty of long-range shooting clubs in Canada.
     
  18. djfly

    djfly Smiter of Spam

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    @skullpirate01

    Picked up something new, do you recognize it?
    (Bipod is borrowed from my .22)



    new.jpg
     
  19. skullpirate01

    skullpirate01 Guest

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    Looks like a bolt-action AR but I know I'm wrong. What calibre is it? Looks like some SPR special forces DMR bow shiet lmao right on~
     
  20. djfly

    djfly Smiter of Spam

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    It's relatively new, JRC JR-9, built in New York.

    - Pistol caliber (9x19mm, .40S&W, .357Sig, or .45ACP)
    - Semi-auto blowback action
    - AR furniture (trigger group, grip and buttstock)
    - Custom buffer tube (to accommodate larger buffer to handle the non-locking action)
    - Fully ambidextrous, just flip the charging handle, ejector, ejection port cover, and magazine release.
    - Tons of Cerakote colours
    - Uses Glock (and recently S&W MP) magazines
    - Available with various foregrips
    - NY SAFE law and California versions available (meaning there's a variant from factory that's non-restricted in Canada)
    - Attention to such details as threading the barrel from factory, picatinny rail machined into the receiver, etc

    I have a slightly taller bipod on order (so I can give this one back to my .22) and I need to figure out what kind of optic I want on it; I'm thinking about a 1-4x24 Vortex

    I've watched/read reviews of guys shooting sub-2 MOA groups (1.15-1.85" groups at 100yds) using pretty standard 115gr ammunition, so I'm absolutely pumped to get it out to the range!

    Also, unbelievably, despite the 18.5" barrel, it's a mere 33.5" long (a full 3.5" shorter than my Marlin 795 in .22LR), and weighs a piddly 6.5 pounds (despite being all metal other than the buttstock) making it a very comfortable bush gun.
     
    Last edited: Oct 13, 2016

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