need help with how much drop to adjust for for 1,000 yards when zeroed in at 100

[slickrock]

I'm fairly new to shooting past 100 - 250 yards and my brother and I have a gentleman's wager on the best out of 3 shots at 1,000 yards. My problem is that I really don't have any where to practice at that distance close buy so when I go to the 1,000 yard range that we have to rent, it will be my first time pushing this far out.

I have a mil-dot 10-40X50 scope. At 100 yards at 40 magnification, cross hairs are dead center of where I am shooting. I know there is a formula to figure out how much I have to adjust by the dots on the elevation of the scope cross-hairs but needs it explained to me or a formula broken down for the mathematically challenged,

The target will be a simple print-out so the the target height will be 11"s tall and 8.5"s wide. Can someone explain to me how I can figure out the formula for bullet drop at 1000 yards with a cope set up for 100 yards?

I'll worry about windage once I see the conditions at the time of the competition.

Thanks, Dan

[a7mmnut]

We'll need a lot more info: Rifle, caliber, load, wind, amount of adjustment on your turrets, the type of mounts you are using....just to start. -7-

[Brian Pfleuger]

You're going to need a target bigger than a single piece of paper.

For the adjustments, no one can tell you without knowing your EXACT muzzle velocity and the bullet you're using.

Use a ballistics calculator like JBM:

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi


Frankly, and I'm being serious here, if you've never shot at 1,000 yards, you need a target that's car sized, not notebook sized.

[1-DAB]

Reloading manuals can get you close, but you need to know more details of your load.

[oryx]

Math without all the numbers is difficult and not very accurate

[g.willikers]

This sounds a lot like a conversation I once had with a neighbor who was a physics professor.
He said his department was once approached to figure out the trajectory for a long range ships cannon.
After much figuring and computer simulations, the only thing that actually came close enough for government work, was just firing the danged thing and see where it landed.

[MTSCMike]

For a .308 shooting 175gr Federal Gold Medal match ammo it is "about" 44 inches of vertical adjustment, if I recall correctly because it's been a while, (up) from a 100 yard zero to an approx 1000 yard zero depending on barrel length, temperature, humidity, etc, etc.

If you hit a target the size of notebook paper at all will be a minor miracle unless you dial close and then shoot some "sighters" to refine your adjustment. The standard 1000 yard target is 6 feet square with a 44" bullseye. The "X" ring is similar in size to the notebook paper so to hit it will require a rifle and ammo that will hold 1MOA at 1000 yards (about 10").

Good luck

[Bart B.]

After getting a zero at 100 yards with Sierra's 30 caliber match bullets, noting the atmospheric conditions and chronographing the load, using Sierra's ballistic software for long range zeros and using local conditions, my first shot at 300, 600, 800 and 1000 yards with three bullet weights and muzzle velocities were within 1/3 MOA of dead on. This is with aperture sights that had to be calibrated for the MOA value each click would make with the non-standard sight radius used on the rifles. Mailed Sierra Bullets an attaboy letter for their excellent software and published BC's for their bullets.

[allaroundhunter]

For a .308 shooting 175gr Federal Gold Medal match ammo it is "about" 44 inches of vertical adjustment, if I recall correctly because it's been a while, (up) from a 100 yard zero to an approx 1000 yard zero depending on barrel length, temperature, humidity, etc, etc.

That is no where close.

It is closer to 375" with that load... About 35 MOA

[MTSCMike]

That's 44 inches at 100 yards...44 MOA...not 44 inches at 1000 yards. I don't think 37.5MOA will get you there. The 44 MOA was on a cold day. Could be more like 42 MOA if the day is warmer.

[Jimro]

allaround hunter,

Really depends on barrel length. 20" barrels can be around 45 MOA if they are "slow" and at standard sea level. A Palma rifle with a 32" tube should be under 35 MOA depending on how hot the load is and what atmospherics conditions happen to be.

Jimro

[allaroundhunter]

Plugging my info into a ballistic calculator puts me at 36 MOA, which is why I said "about". 26" Barrel, 175 gr SMK, .496 BC, 2665 fps, 800 ft elevation and 85 degrees.

Yes, it does depend on barrel length, muzzle velocity, BC, and other factors. What I was getting at was that 44" is not the holdover.

I now see that that is not what MTSCMike meant by it, but that is what it came across as. Since the OP asked what his holdover should be, I didn't want him to go out and hold 4ft over his target at 1,000 yards with a 100 yd zero and expect to be close...

[Jimro]

Holdovers are definitely not for a shot that long, although if you are good enough to holdover out to 1k, you would be aiming thirty to forty feet over your target, which is usually outside the viewing area of a scope at max magnification. Not something I would care to try.

Jimro

[allaroundhunter]

I'll worry about windage once I see the conditions at the time of the competition.

Out of curiousity, slickrock, just how much do you think a 5 mph crosswind (a slight breeze felt on the face) from 3 o'clock will affect a bullet's impact at 1,000 yards relative to your point of aim?


I think that both you and your brother are way out of your leagues with this "wager". Trying to hit a target that is under 1MOA width-wise and barely over 1MOA height-wise at 1,000 yards without ever shooting much past 250?...

Call me a pessimist.... but I would bet that even given 20 rounds each there would not be a hit on paper.

[kraigwy]

I would bet that even given 20 rounds each there would not be a hit on paper

Using your 5 MPH wind at 3 O'Clock with the 175 SMK @ 2600 fps is going to drift about 40 inches or 4 MOA.

A "1" MOA target is going to be 10 inches in diameter.

Somebody is gonna have to "crank in" some windage.

[allaroundhunter]

That's exactly what I was saying, kraigwy. I don't think the OP or his brother really have an idea of what they are trying to do, nor how hard it is.

You can't go out to a 1,000 yard range and send 3 shots and expect to hit a target that is 1MOA x .8MOA. Especially if you have rarely ever shot past 250 yards.

[Tempest 455]

Ditto on above comments. We just shot our first F/TR class last weekend at 1,000 yards. My rifle was zero'd at 400 and capable of .5 MOA on a good day.

However, at the 1,000 yard match, getting sighted at 1,000 took us probably 20 rounds on a 5 foot target to figure out the correction and I had literally spent hours on JBM checking numbers. In our case, it was my fault, I had forgot to re-zero the windage turret before we went. I had been shooting in 15 MPH winds prior to the match.

Point being, we got some 9's, 10's and 1x and it was a lot of fun, but I can't see anyway possible hitting a sheet of paper at 1,000 unless you are already dialed in for 1,000, are seasoned and know what the wind is doing.

[bamaranger]

My F-T/R rifle (175/.308) come up from 100 is 37 MOA f0r 1000. That will ususally put me in the black, but ranges, conditions vary and more vertical adjustment is usually necessary.

What the OP wants (I think) is what mil-dot to use to shoot at 1000 yds if he is zeroed for "on" at 100.

Don't think that is gonna work,..... not enough dots!

[jughead2]

guess my son didnt do to bad with his first and only try then. 3ft square paper with spray bomb lid in the middle. 4 shots covered by a basket ball and one flyer about 5 ins. away. marriage ended things abruptly after that. oh lid was in the center of the 4 shots

[Jim Watson]

My 100-1000 comeup is 35.5 MOA with 175 gr SMK loaded a bit faster than factory match .308. It is Something Different with 155 gr Scenars. I could look it up but since we don't know what the OP is shooting, it probably doesn't matter.

[allaroundhunter]

It is Something Different with 155 gr Scenars. I could look it up but since we don't know what the OP is shooting, it probably doesn't matter.

No need to look it up, I've got it on the top of my head ;)

155 gr Scenar at about 2,950 fps: Come-up is 29 MOA at 1,000 from a 100 yard zero.

[Tempest 455]

Speaking from memory (I have it in my log book, so don't quote me) you can shoot out to 800 yards with a 400 yard zero using mil dots. We did that shooting steel one time. But like you said, you wont have enough mil dots to get to 1,000 and need to be zeroed farther. Not to mention, not the most precise way to shoot.

[allaroundhunter]

Speaking from memory (I have it in my log book, so don't quote me) you can shoot out to 800 yards with a 400 yard zero using mil dots. We did that shooting steel one time. But like you said, you wont have enough mil dots to get to 1,000 and need to be zeroed farther. Not to mention, not the most precise way to shoot.

It all depends on the magnification range of your scope and whether you are using a FFP or SFP reticle.