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August 09, 2013

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Jack

There is a theory that if you sight a rifle in to hit a bullseye at 25 yards, that the rifle will be back on the bull at 100 yards. I've tried it and found that it was nonsense, at least the way I shoot.

I always sight my rifles 3" high of the center of the bull at 100 yards. With that, they can be shot at point blank range with a hole somewhere in the center of the circle and they are usually back on at 250-275 or require a 6-8" hold over on 350-400 yards, depending of course upon the specifics of the individual cartridge.

In any event this is a rule of thumb and because every shooter is different each shooter should take his gun to a range and find out exactly where his specific round is going. Switch rounds and you'll have to start over.

guy

With 7.62x39 out of a 16.25"(AK47) barrel a 25 yard zero will also be a 200 yard zero. And 3.6" high is the worst you'll be off anywhere in between.

Works out really nicely in my opinion.

john jay

guy:

in theory. but, as noted by jack, it all requires verification with actual shooting at known distances.

and, you must know the bullet, and the muzzle velocity from your arm, to be really precise.

jack:

i am in general agreement, but, as you note, it is all pretty highly variable, and anything different requires a different set of shooting solutions.

this trajectory business is based on a lot of factors, to include velocity of the bullet, the shape and weight of the bullet, ambient temperatures and the like. the height of the line of sight above the line of the bore has a tremendous impact upon aiming, and resultant trajectory to the target.

and, again, all the shooting solutions in the world, and all the methods used to arrive at them, require verification.

all of these things dictate whether you can hit a medicine ball at 350 yards, or whether you can reliably hit a baseball at such a distance from a cold barrel with the first shot.

and, one factor that's not been mentioned, is knowing the distance, almost to the foot at extended ranges.

it is a very complex subject, this long range shooting, and not easily comprehended by rule of thumb solutions.

i wish i could recite authority and appropriate links, but most of what i know i've learned from a group of fellows here in north east oregon who are skilled long distance shots.

they carry with them kestral weather stations that measure wind and barometric pressures, and have calculators that provide shooting solutions to be dialed into precision optics that consider gps fixed position, direction of the shot, effect of the spin of the bullet and the spin of the earth, and god knows what else.

holding the slick side of your thumb up to the wind just doesn't do it.

(and, as a matter of fact, though "height" is relatively easily accounted for, reading "windage" is an acquired art form, and requires a lot of shooting time. there is no substitute for time behind the stock. and, shooting.)

john jay

CharlieL

When I was in basic training, oh, 50 years ago we were taught to set our sights for a 25 yard zero, called a battlesight zero.. This was for combat use, as explained to us (aim for center mass), and were told that on the way down, the round would cross the sight path at right about 250 yards. This was with M-14s, 7.62NATO.
We were also told the ballistics were very close to the Garand 30-06.
Could anyone who trained with a Garand tell me if they got the same information?

john jay

charlie:

see the comments above.--

this seems to be more or less the approach the military has followed, at least the army, in teaching "marksmanship."

i've got a short post in reply to the above, because the assholes at typepad cannot seem to print my submissions to my own comment section.

sheesh.

john jay

Jay Dee

I haven't pulled out my ballistic software but your essentially correct. The bullet starts out below the line of sight. Depending on the velocity, ballistic coefficient & sight in range, the bullet will cross the line of sight somewhere between 15 & 25 yards. Closer sighting ranges moves this crossover point further away.

My 222 Magnum would cross the line of sight at 17 yards to sight in at 225yards. The bullet was never more than 1.5 inches above the lineb of sight at 100 & 150 yards.

drew458

The 25yd zero is a nice idea, but the point blank range you get all depends on the cartridge and the bullet.
Sighted in at 50 feet, my .44 mag rifle is spot on at 100 yards.

To get any use out of these short range trajectories, you have to plot the whole trajectory. Not much point sighting in a pokey old .45-70 at 25 yards if you want to hit a 200 yard bullseye. Plot the curve, then adjust your sighting in point

john jay

drew:

yes, agreed.

not everyone wants to go to the work and expense of getting these trajectory matters squared away.

again, it comes down to what is serviceable accuracy for a person.

baseballs, refrigerators, volkswagen beetles at 350 yards? some people claim long range hits using "kentucky windage" methods, but i remain a bit dubious.

john

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