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Posted: 12/28/2010 5:09:35 PM EDT
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I was shooting today at 25M to see what ammo my Kimber 82G likes. I shot at 25 M because the wind was a bit of an issue. I was wondering, since I plan on shooting this rifle at mainly 50M how much will a 25M group spread out in another 25M. I guess what I am asking is If everything other than the distance was exactly the same and the group was a bit under 1/2" what would that group spread out to at 50M? Thanks for reading my rambling post.
ERic |
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Nearly an inch.
Accuracy tends to degrade with distance, 2 minutes @ 25 likely will be a little bigger @ 50, bigger still @ 100. I'll be shocked if that thang won't punch one somewhat ragged hole @ 25 with SOME ammo. You'll have to use a lower sight setting, too. |
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If it's windy enough to actually feel then don't worry about your groups that day with .22LR...
Wait for a totally windless and preferably cloudy day. That gun in good condition should hold about 2" at 100 yards with match quality ammo that it likes (Eley Match/Tenex/etc..) It's not an easy thing though. Your technique needs to be pretty perfect to get a 5-shot 2" or better group at 100 with .22LR in a bolt action... |
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Quoted:
Nearly an inch. Accuracy tends to degrade with distance, 2 minutes @ 25 likely will be a little bigger @ 50, bigger still @ 100. I'll be shocked if that thang won't punch one somewhat ragged hole @ 25 with SOME ammo. You'll have to use a lower sight setting, too. I am confused. 2 MOA at 25 is half inch. at 50 it will certainly be a little bigger - it will be one inch, but that is still 2 MOA. Bigger still at 100 is still 2 MOA. But all of these can be with the same accuracy - 2 MOA. I hope I haven't misunderstood something you wrote, if so my apologies. I suppose accuracy could degrade with distance due to wind, spin drift, or some other external ballistic factor. If OP is getting half, inch at 25, this pattern should be an inch at 50, inch and a half at 75 and 2 inches at 100. All of these are "two minutes of angle." |
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Quoted:
Quoted:
Nearly an inch. Accuracy tends to degrade with distance, 2 minutes @ 25 likely will be a little bigger @ 50, bigger still @ 100. I'll be shocked if that thang won't punch one somewhat ragged hole @ 25 with SOME ammo. You'll have to use a lower sight setting, too. I am confused. 2 MOA at 25 is half inch. at 50 it will certainly be a little bigger - it will be one inch, but that is still 2 MOA. Bigger still at 100 is still 2 MOA. But all of these can be with the same accuracy - 2 MOA. I hope I haven't misunderstood something you wrote, if so my apologies. I suppose accuracy could degrade with distance due to wind, spin drift, or some other external ballistic factor. If OP is getting half, inch at 25, this pattern should be an inch at 50, inch and a half at 75 and 2 inches at 100. All of these are "two minutes of angle." He means the accuracy will tend to degrade parabolicly with distance. So a .22LR rifle that holds MOA (~1 inch) at 100 yards will very likely be much worse at 200 yards, say 3 MOA (6"). The accuracy degrades for all the reasons you mentioned plus 100 other variables. |
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Any time you're shooting to measure accuracy, you have to read the wind, otherwise you're really wasting your time and will come to incorrect conclusions.
First, put up a rudimentary wind flag. Just a piece of surveyor's tape hanging from a stick will work in conditions that are easy to feel. Set it up no more than one quarter the distance to your target. If you have to err, set it closer to the rifle. In really light conditions, hang a piece of old school cassette tape. Try to shoot when the flag is hanging in the same orientation for every shot - but also when the conditions at the bench and down the range are the same. Then pay attention to the breezes you can feel, and understand how wind from each direction will affect how the bullet flies. This chart, Bullet Impact in the Wind, will help you understand where the bullet will land in breezes coming from every clock direction. These are real effects that require compensation. Also pay attention to structures behind the range and terrain along the range, and try to understand how the airflow is affected. Some time when the air is calm, set a few smoke bombs on the range from the bench to the target. That can be an eye opener. Learning to pay attention to the wind at the bench will pay off in the field. You'll feel a breeze and know how to compensate, or whether to wait. |
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Quoted:
Quoted:
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Nearly an inch. Accuracy tends to degrade with distance, 2 minutes @ 25 likely will be a little bigger @ 50, bigger still @ 100. I'll be shocked if that thang won't punch one somewhat ragged hole @ 25 with SOME ammo. You'll have to use a lower sight setting, too. I am confused. 2 MOA at 25 is half inch. at 50 it will certainly be a little bigger - it will be one inch, but that is still 2 MOA. Bigger still at 100 is still 2 MOA. But all of these can be with the same accuracy - 2 MOA. I hope I haven't misunderstood something you wrote, if so my apologies. I suppose accuracy could degrade with distance due to wind, spin drift, or some other external ballistic factor. If OP is getting half, inch at 25, this pattern should be an inch at 50, inch and a half at 75 and 2 inches at 100. All of these are "two minutes of angle." He means the accuracy will tend to degrade parabolicly with distance. So a .22LR rifle that holds MOA (~1 inch) at 100 yards will very likely be much worse at 200 yards, say 3 MOA (6"). The accuracy degrades for all the reasons you mentioned plus 100 other variables. Fearme (and others) I hope you will give me room to disagree with you some, and please don't take offense. there is a lot that is not in contention. First, 2 MOA is a fine group for many rifles. Second, many shooters have trouble shooting long distance - this is a criticism of the shooter, not his rifle. third, when you are talking about external ballistics and the environmental factors that can effect a change on accuracy, there are many, including wind, extreme temperature shifts, spin drift, Precession. Rain and the Coriolis effect have become "busted" myths for conventional centerfire rifles. I think in most rifles, accuracy will NOT degrade with distance. In fact, there was a very heated thread on just the opposite phenom - that the accuracy of many rifles can actually increase with distance (distance greater than 300 yards in most cases.) This is the thread on "corkscrew effect" and bullet "precession." In your example, a rifle that shoots 1 MOA (which is 1 inch at 100 yards) may not shoot 1 moa at 300 yards (in other wirds, the group may be larger than 3 inches). If this is the case, it may be because the shooter was only firing 3 round groups (see Molon's thread on the trouble with 3 shot groups) it may be because of other rifle/shooter error such as an understabilized round. Your example was for .22 LR, which has it's own science/art if you ask me and may not be the best example. In most cases absent external factors and errors, a rifle that shoots an inch at 100 yards will normally shoot 3 inches at 300 yards, or better. The problem is normaly shooters who fail to record data in a statistically valid way, such as by only firing 3 round groups. So I'm all ears on this - maybe you guys can show how a rifle can be less accurate at a distance of >100 yards. |
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The 2 MOA was a f'rinstance based on OP's group size.
And while I agree with many of FordGuy's comments (based on the bullet "going to sleep", I think), there was a discussion a while back (RFC, IIRC) about somebody bent out of shape about statements of "XMOA @ Y distance" the contention that a half minute is a half minute at any distance, and that a half minute gun (or whatever reference standard) is capable of that standard to the limit of that cartridge, which I consider BS. Lots of gun/cartridge combinations that can shoot to a given standard can't shoot to the same standard at a greater distance. Benchrest guys shooting for fractional MOA @ 100yd don't give a FPF about 200yd accuracy. It will usually be real damn good, but oftem more than twice the group size of 100yd. Crap, I think maybe it was you, FG. Can we agree to disagree again? |
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The 2 MOA was a f'rinstance based on OP's group size. And while I agree with many of FordGuy's comments (based on the bullet "going to sleep", I think), there was a discussion a while back (RFC, IIRC) about somebody bent out of shape about statements of "XMOA @ Y distance" the contention that a half minute is a half minute at any distance, and that a half minute gun (or whatever reference standard) is capable of that standard to the limit of that cartridge, which I consider BS. Lots of gun/cartridge combinations that can shoot to a given standard can't shoot to the same standard at a greater distance. Benchrest guys shooting for fractional MOA @ 100yd don't give a FPF about 200yd accuracy. It will usually be real damn good, but oftem more than twice the group size of 100yd. Crap, I think maybe it was you, FG. Can we agree to disagree again? LOL, I don't think it was me but maybe. I am a student of ballistics, not a teacher.  And I consider you a smarter guy then me so I defer to your opinion on this frog. I appreciate all the civility over a topic that has been known to result in bickering. We sure can agree to disagree frog. cheers brother.
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Things to consider.....
Environment: wind, rain, pressure, etc. Bullet: BC, when does it drop out of the speed of sound, etc Bench set up: Stable rest, flags, etc. Rifle: Trigger, stock, barrel, clean?, Scope, mounts, etc. Shooter: can you keep it together? If you shoot 1 MOA at 25M, you may or may not shoot 1 MOA at 50M......it's not so much accuracy.....it's repeatibility. Yes, group size opens up as you go out in distance (cone of fire).....however it will not be linear....it will be exponential. A 1 MOA group at 25yds may open up to a 1.5MOA group at 100yds. |
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Things to consider..... Environment: wind, rain, pressure, etc. A lotof people think wind and rain don't play the havoc you think it does. Bullet: BC, when does it drop out of the speed of sound, etcn thats why you shoot subsonics Bench set up: Stable rest, flags, etc. Rifle: Trigger, stock, barrel, clean?, Scope, mounts, etc. cleaning your barrel may not have the effect you think it does. Shooter: can you keep it together? If you shoot 1 MOA at 25M, you may or may not shoot 1 MOA at 50M......it's not so much accuracy.....it's repeatibility. Yes, group size opens up as you go out in distance (cone of fire).....however it will not be linear....it will be exponential. A 1 MOA group at 25yds may open up to a 1.5MOA group at 100yds. |
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