MOA Accuracy
In theory, disregarding gravity, if rounds which formed a MOA group at 100 yards continued to 600 yards, disregarding gravity again, would they result in a MOA score at that range?
Sage 1[:D][:D][:D][:D]
Sage 1[:D][:D][:D][:D]
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MOA is minute of angle. It refers to the angular dispersion of a shot group, not the size. A one inch group at 100 yards is nominally 1 MOA, and a 6 inch group at 600 yards is nominally 1 MOA. 0 -
In theory, yes
In reality, often not.
You can find loads that group sub-MOA at 100 and than fall apart at 200 (and can't even find paper at 300) and you can find loads that are MOA+ at 100 and sub-MOA at 200yd and beyond.
It's not the gravity or wind, it's bullet stability that causes the changes in MOA groups.
Gravity is a constant that causes the bullet to drop, wind causes the bullets to drift sideways (and shifting winds down range can realy mess with your mind)0 -
Hello I can't speak for rifles past 200 yards but I can address pistol loads. It is IMHO that the correct twist for the weight and velocity of the bullet itself can be a MAJOR factor in any firearm as the range increases and the bullet may become unstable and group size goes to He** I have been looking for that magic small group for 30+ years in 45ACP with 230 grain bullets at 830 FPS the group size between 25 yards and 50 yards can be as small as 1X at 25 yards 2.5X at50 yards drop the velocity to 700 FPS and it goes to 1X at 25 yards and 5X at 50 yards . In another case with cast 200 grain bullets again at 800 fps quality bullets 1X at 25 yards and 2.2X at 50 yards same bullet but not sorting by weight and quality 1X at 25yards 8X at 50 yards. All groups with pistol in ransom rest the X in these examples = the size of the group for 10 shots this changes with powder /primers and OAL of each loading. "PRAISE THE HARD-BALL GUN" 0 -
In theory, yes, a one MOA group will be a One MOA group at a farther distance.
In reality, the target looks immensely smaller, wind has a much bigger effect when you stretch out distances. Imperfections in velocity really start to magnify. Two rifles zeroed @ 100, but one is pushed 200 fps slower. The drop difference from 100-200 is 1/2". 200-300 is 2". 300-400 is 4" See how that grows.
Of course there is stability. I don't usually run into that. Unless, I'm out to 1k and have a bullet that doesn't stabilize through the transonic range (according to some that is now a myth) The bullet just goes unstable..it just seems to happen around the speed of sound.[:0][;)][:D] It may or may not become stable again. Bryan Litz' theory is rotating the bullet more will not only keep it stable through the transonic range but beyond it as well. Meaning go with the tighter twist if you are getting a new barrel.0 -
BUT, if you spin them to fast, it takes further for them to steady down (some high faluting phrase like "precessing around the line of flight"), which is where the larger groups at close range/tighter at long range tend to show up. And, if you spin them way to fast, the jacket tends to rupture and than (due to centripital force) nothing hits the target (but you do get a cute little blue puff of vaporized lead in the air)[:D]
Edit to not burn another reply
Here's a little light reading on the subject of bullet flight
http://www.nennstiel-ruprecht.de/bullfly/index.htm
And if realy want to understand it, might I suggest studying this online book (the definitive study of ballistics).
http://books.google.com/books?id=QdQqAAAAYAAJ&printsec=frontcover&dq=the+bullet's+flight&cd=1#v=onepage&q=&f=false0 -
quote:Originally posted by Sage1
In theory, disregarding gravity, if rounds which formed a MOA group at 100 yards continued to 600 yards, disregarding gravity again, would they result in a MOA score at that range?
Sage 1[:D][:D][:D][:D]
Yes.
MOA (minutes of angle) refers to spread in radial degrees, with one "minute of angle" being 1/60 of a degree.
If you shot the bullets in a hypothetical frictionless and gravity-free environment (eg through outer space), then 1 MOA at 100 yards would equal 1 MOA at 200 yards, at 300 yards, at 1000 yards, at 10,000 yards, etc.
Of course the real world has gravity, air friction, wind, temperature variation, humidity variation, and other variables to mess up this theoretical physical/mathematical perfection.
So in the real world, in *general* rifles that shoot to 1 MOA at 100 yards will shoot slightly wider groups at 200 yards, slightly wider groups yet at 300, etc.
There are certain exceptions where projectiles may be more accurate at certain greater distances compared to nearer ones because of bullet spin/stability issues, but even there, accuracy will tend to peak at a certain distance, then again begin to degrade further downrange after that point.0 -
Well without gravity a bullet wouldn't need spin stabilization to start with... If it wasn't for gravity an object would travel on the same path, and MOA wouldn't be an issue at all. You wouldn't even need a barrel if it wasn't for gravity, you'd just need a force to hit the object on the backside in the exact direction you'd want it to go. Newtons law, an object in motion stays in motion. Literally if something was traveling thru space, and there was no type of energy or gravity or anything to effect its travel, it would continue in an exact straight line travel forever. It wouldn't matter if it was 100 yards or 100 trillion yards.
Now here's the funny thing. If there was another object behind it traveling in the exact same path, depending how much mass the two objects have would effect how long it takes for the object in front to speed up the object behind it and the object behind it to slow down the object in front to eventually stop and orbit each other because all objects have mass which has gravity.0 -
quote:Originally posted by leeblackman
Well without gravity a bullet wouldn't need spin stabilization to start with...
If you wanted to shoot accurately over distance, you would still need it because of air resistance and wind. A non gyroscopically spin-stabilized bullet could be easily deflected off its long-axis first flight path by a breeze, eventually tumbling end over end. Unpredictable tumbling through air would not only decrease accuracy, it would also reduce velocity and cause the bullets not to strike the target nose-first.
Using perfectly spherical bullets might avoid most of the issues regarding tumbling, but those sorts of bullets aren't all that aerodynamic and would again lose velocity quickly in comparision to more conventional ones with excellent ballistic coefficients.
quote:If it wasn't for gravity an object would travel on the same path, and MOA wouldn't be an issue at all.
Not entirely true.
While in zero-gravity the path of moving objects should approximate a straight line, a fundamentally inaccurate gun fired in a zero-gravity environment is still going to be inaccurate. . .even assuming no air or other friction during flight.
Gravity doesn't play any significant role in shot-to-shot variations in bullets, powder, primers, barrel vibration, barrel-to-stock movement, barrel cleanliness, and all of the other factors generally correlated with conventional firearm accuracy.
Put differently, your Hi-point wouldn't turn into a match-quality pistol just because you took it into a zero gravity environment!
quote: You wouldn't even need a barrel if it wasn't for gravity, you'd just need a force to hit the object on the backside in the exact direction you'd want it to go. Throwing a bullet at something with your hand might eventually get it there in a zero-friction gravity-free environment, but it wouldn't do any damage when it hits!
If you want to launch a projectile at a high velocity from a conventional firearm, you'd still need a chamber and barrel to contain the expanding hot gases and direct the bullet even in a zero-gravity environment.
quote:
Newtons law, an object in motion stays in motion. Literally if something was traveling thru space, and there was no type of energy or gravity or anything to effect its travel, it would continue in an exact straight line travel forever. It wouldn't matter if it was 100 yards or 100 trillion yards.
This is true, but again, the real world has friction, gravity, etc.
There is even friction in the "vacuum" of outer space because in reality the supposed vacuum isn't entirely empty, containing as very sparse population of hydrogen molecules.
At ordinary velocities and in ordinary human time frames, this friction is negligible, but if you were to say, try to build a craft to slowly accelerate to light speed, you'd find that you'd have to expend enormous amounts of energy to overcome the vast ocean of hydrogen you'd be pushing your craft through.
quote:Now here's the funny thing. If there was another object behind it traveling in the exact same path, depending how much mass the two objects have would effect how long it takes for the object in front to speed up the object behind it and the object behind it to slow down the object in front to eventually stop and orbit each other because all objects have mass which has gravity.
If you want to get into silly theoretical physics constructs, again *in theory* every particle of mass in the universe exerts a gravitational force on every OTHER particle of mass in the universe.
That means in your hypothetical "empty world" containing absolutely nothing but two projectiles starting in a frame of reference with zero relative motion, no matter HOW FAR apart, the two would exert gravitational force on each other, eventually either colliding or orbiting one another (or both). Sure it might take trillions of eons before either accelerated enough to demonstrate perceivable motion, but that's why this is a theoretical empty world. . .nothing else is going on, so you might was well wait!0
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