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Thread: Question for the experts

  1. #1

    Default Question for the experts

    What kind of groups should I be making at 100 yards to have suitable 400 yard accuracy? For example, If I am shooting 2.5 inch groups with my .260 rem, would my groups be too spread out to even think beyond 200 yards?

    Thanks in advance!

  2. #2
    Member Float Pilot's Avatar
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    If you are really shooting 2.5 inch groups right now, they will equate to a 10 inch group at 400 yards. Enough for a Moose shoulder or Deer's chest.
    Depending on what you are using for sights and a few other varibles.

    What is your rifle, sighting system and how are you positioed while making these shots?
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  3. #3

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    Basically, everyone has an opinion on "acceptable accuracy" out of their rifles. What I've heard of the .260 Remington, I believe most any rifle chambered for that cartridge should be capable of shooting sub-MOA groups. That means 1" group or less at 100 yards. As Float Pilot said, that would be good enough for hunting accuracy on a deer or moose. My personal opinion has always been that a rifle that can't be made to shoot under 1" at 100 yards off the bench isn't worth having. If a rifle will only shoot 2.5" at 100 yards off the bench, think of what kind of wobble radius you'll have when you're out of breath, leaning over a rock, shooting at something at 300+ yards. Just my $.02.
    NRA Life Member, Prior F-16 crew chief.

  4. #4

    Default 400 Yard Groups

    On a rare occasion, your 400 yard groups will actually be just 4X of 100 yard groups.Generally, they will be much larger.

    Why? For openers, wind drift will be much more pervasive at 400 yards, as the bullet (regardless of its actual BC) will be traveling much more slowly. Additionally, your ability to achive a perfect sight picture at 400 will never equal the same picture obtained at 100.Issues such as mirage can also interfer more at 400 than 100.Finally, in non parallax adjustable scopes, set typically at 150 yards by the factory, this issue will also degrade total group size.

    Shooting small groups is dependent on many factors.Books are written about all the issues that go into making rifles produce small groups.In many cases, we are measuring the ability of the shooter more than the firearm/sighting apparatus when we measure group size.Put a known to be fantastic bench gun in the hands of an untrained shooter with mediocre technique and group size will double or triple immediately.

  5. #5

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    I am not sure a ruger rifle was the best choice for the 260. However on the bright side i dont reload and with remington factory loads I can shoot 1.5 inch groups. It is the federal loads that are 2.5 inches.

    To pick you brains a little more, What would a 1 inch group equate to at 300 400 and 500 yards? This is some important math I am learning. Thanks

  6. #6

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    Accuracy-wise a 1-inch group would certainly improve the odds of making hits at those ranges, but when you say "adequate" you open the question of energy, bullet construction, field factors such as wind and range estimation that determine where they land, and species of game. Therefore adequacy depends a lot more on your choice of game and the fine details that determine how well you can put the bullet where you want it, irrespective of group size from the bench.

    I think the Ruger is a great rifle for the 260, BTW. I'm betting that between reloading or a change in ammo and a little rifle tuning you can shrink that group a lot.

    But on the other hand my most "accurate" gun for big game hunting won't do any better than 2.5" at 100 yards. It's my most accurate hunting gun in spite of the relatively large groups because it is so dogone easy for me to shoot well offhand and from other field positions. It's a 7x57, and I'm pretty sure I could shrink the groups with further load development and even some rifle tuning, but I'm never going to be shooting game much past 300 with it, and more often I'm shooting inside 100 and offhand. I quit messing with load development and started loading masses of ammo for offhand practice many years ago, and just haven't got around to going back and seeing if it will do better.

    And other factors aside, technically a 1" group at 100 would translate into 2" at 200, 3" at 300, 4" at 400, and 5" at 500, but sighting errors, wind and many other factors tend to enlarge groups beyond potential as range stretches.

  7. #7
    Member JOAT's Avatar
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    Use this formula:

    Group size = tan(MOA/60) * distance

    Note group and distance are inches (100 yards = 3600 inches, etc.)

    Using the "standard" of a 1 MOA gun, the group sizes can be found by multiplying the distance (in inches) by 0.00029088821687 and you'll get the theoretical group sizes for the various distances.

    100 yards = 1.047"
    200 yards = 2.094"
    300 yards = 3.142"
    400 yards = 4.189"
    500 yards = 5.236"

    You'll note that each distance is simply a multiple of the 100 yard group. Therefore, whatever group you shoot at 100 yards can be multiplied by the desired distance divided by 100 and you'll have the theoretical group size at that distance. Example, for 200 yards, divide 200 by 100 and you get 2. Multiply 2 by the group size at 100 yards. For 350 yards, you would multiply the 100-yard group size by 3.5, etc.
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  8. #8
    Member Alangaq's Avatar
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    I have no experience with the Ruger in 260 but my wife has a Rem model 7 in 260 that will put 5 shot into an inch at 100 yards using the Remington 140 gr load. After the barrel heats up some it will start to string them out a bit but not that bad. Pretty darn good accuracy for a 20” barrel that is the diameter of my pinky finger. I have been able to consistently keep 5 shots in about 8 inches at 300 meters out at North Birchwood from the bench. If the wind is calm, and I am calm, then I can shrink those down quite a bit, but not to 3” I have found that for me at least, the math doesn’t really mean squat when you are shooting hunting rifles from anything other than a bench rest without the use of a high magnification scope. That being said, just what the hell are you going to shoot at that is 400 yards away? I know a lot of guys that claim to have shot this or that at 400 + yards, and I tend to think most of those “range estimates” are bunk. I am not saying it isn’t possible, or doesn’t ever happen, but it sure don’t happen as often as people say it does. 400 yards is a dang long ways and you need a good steady rest, accurate rifle and ammo, and a calm mind and body to consistently make kill shots at that range. I guess I always ask myself, wouldn’t it be better to stalk up a little closer than to risk a long range shot that could go bad and just wound the dang critter. I personally like stalking a hell of allot more than tracking! Anyhow, to answer your original question, I would speculate that from your rifle, you should expect about 10” groups at 400 yards. I aint got no math or slide rule to substantiate that figure, but its my 2 cents worth and its worth exactly what you paid for it.
    “You’ve gotten soft. You’re like one of those police dogs who’s released in to the wild and gets eaten by a deer or something.” Bill McNeal of News Radio

  9. #9

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    I believe Carlos Hathcock's M70 3006 was a 2 MOA rifle, due to peppered bore. He did pretty good on smaller targets.

    Side bar:sometimes guns shoot a little better at 400 than 200, as the bullet settles down, so the theory goes.

  10. #10

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    Alagaq makes a really good point: what do you plan on shooting at that distance? If you really want a 400-yard hunting rifle, maybe you should look to a magnum cartridge that was designed to shoot those kind of distances. I've got nothing against the .260, but 400 yards is definitely a stretch of the barrel to have much oomph left to knock something over, especially if it's a very big critter. For many years I carried a Model 7 in 7mm-08 and was very happy with its performance. I knew the rifle and was very deadly with it out to 300 yards or so. Anything very much farther than 300-350 was kind of iffy though because it just doesn't pack the punch when I was only getting 2900 fps out of a 120. BrownBear also made a good point about a "shootable" rifle. Whatever rifle you plan to hunt with, there's really no substitute for putting a whole bunch of rounds downrange in the off season. The more you shoot a rifle and become familiar with it, the better you'll shoot it and the more confidence you'll have in it.
    NRA Life Member, Prior F-16 crew chief.

  11. #11

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    Good point. For the 260 will shoot good at 400 with match bullets as far as grouping, what is the lethality for hunting? The best shooting bulelts are not generally recommended for hunting game.

    Is there a measure, such as minimum energy, recommended or required to ethically kill an animal quickly and humanely?

  12. #12

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    Until you shoot at 100, 200, 300 and then 400 you won't really know and it will just be a guess. Some loads group great at 100yds but not at 400 and some loads group great at 400 but not so great at 100yds. Until you go and shoot your loads and measure them at these distances it is just a guess. Anyway, if you are going to shoot at long ranges you need to be shooting in practice at long range.
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  13. #13
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    Default Cool math...

    Quote Originally Posted by JOAT View Post
    Use this formula:

    Group size = tan(MOA/60) * distance

    Note group and distance are inches (100 yards = 3600 inches, etc.)

    Using the "standard" of a 1 MOA gun, the group sizes can be found by multiplying the distance (in inches) by 0.00029088821687 and you'll get the theoretical group sizes for the various distances.

    100 yards = 1.047"
    200 yards = 2.094"
    300 yards = 3.142"
    400 yards = 4.189"
    500 yards = 5.236"

    You'll note that each distance is simply a multiple of the 100 yard group. Therefore, whatever group you shoot at 100 yards can be multiplied by the desired distance divided by 100 and you'll have the theoretical group size at that distance. Example, for 200 yards, divide 200 by 100 and you get 2. Multiply 2 by the group size at 100 yards. For 350 yards, you would multiply the 100-yard group size by 3.5, etc.

    I like, nice touch, it even works.

    A minute of angle is a 60th of a degree.
    Therefore an MOA or two is a fraction of a degree and the trig tables are extracted from degrees or fractions thereof, sooooo...then * the distance (in inches or yards*36) and voila the inches of the expected group.

    Question: Does MOA describe a group size or the amount of error?

    MOA at 100 as you pointed out is 1.047" but for a rifle to shoot with MOA accuracy doesn't that mean that it will be within, + or -, one MOA or specifically 2.094" at 100 yards? A minute of angle to the left or a minute of angle to the right, or up or down. Isn't that an MOA rifle?

    Just thinkin' or trying to.
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  14. #14
    Moderator Paul H's Avatar
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    Dittos on the only way to know how your gun performs at longer range is to actually shoot at that range. I've seen some loads that are mediocre at 100, say 2", that grouped quite well at longer range, i.e. 5" at 300.

    No offense, but if you're only grouping and practicing at 100, and your groups are 2 1/2", you need to put the targets out at longer ranges before attempting long range shots at game.

  15. #15
    Member JOAT's Avatar
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    Default MOA Formula

    Quote Originally Posted by Murphy View Post
    Question: Does MOA describe a group size or the amount of error?

    MOA at 100 as you pointed out is 1.047" but for a rifle to shoot with MOA accuracy doesn't that mean that it will be within, + or -, one MOA or specifically 2.094" at 100 yards? A minute of angle to the left or a minute of angle to the right, or up or down. Isn't that an MOA rifle?

    Just thinkin' or trying to.
    Digging back into trig & algebra... the formula is a little awkward with shooting because MOA is minutes of angle and is an absolute angular measurement. So it describes the angle that would be created if you draw two lines from the opposite outer edges of your shot group back to the gun muzzle, forming a really long and thin triangle.

    To be useful, you really have to work the formula backwards. In other words, you shoot a group, and then plug in your known values, which would be group size and range. Then the remaining variable is MOA and you can solve the formula and find the exact angular measurement for that group and therefore what the "MOA" you and your gun shot for that one group. Naturally, every group you shoot is going to come back with a different MOA, which is why this doesn't fit "perfectly" into shooting.

    For this case where he is shooting 2.5" groups at 100 yards, the "MOA" for that shooter/rifle/ammo combination on that day was 2.387. So if he pretty consistently grouped 2.5" at 100 yards, you could probably call that an average MOA and use it to figure groups at various distances with the original formula. But all that math doesn't make much sense when the change in theoretical group is linear over distance.

    That's why I think the formula's real value is in determining MOA, not group size. So using that rusty old algebra, the more useful formula should look like this after rearranging it a bit (all measurements in inches):

    MOA = arcTan (group/distance) * 60

    Does that sound better?
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