The kids and i went out with the neighbor in north dakota to sight in the rifles for hunting & he told me a scope formula for distance, like 25 yds same in the scope as 100 yds, but adjust 1/4 inch for 50 yds and 1/2 @ 75, or something to that effect. does anyone know the exact formula?
Scope formula
- Thread starter Shell
- Start date
There is no such animal.
The caliber, the scope, the bullet, muzzle velocity, the height of the scope above the bore all factor in.
If you really want to know, punch your numbers in here:
http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
The caliber, the scope, the bullet, muzzle velocity, the height of the scope above the bore all factor in.
If you really want to know, punch your numbers in here:
http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
bailey bud
New member
Art Eatman
Staff in Memoriam
For a low-mount scoped rifle, as a generality for most cartridges with a muzzle velocity around 3,000 ft/sec, give or take a bit: Dead on at 25 yards is around two to three inches high at 100 yards. Might be an inch or two off, but easy to then get sighted in.
Mostly, two inches high at 100 will be right at dead-on at 200 and about six inches low at 300 yards.
This omits magnums, hot-shot .22 centerfires and cartridges in the .30-30 class.
Mostly, two inches high at 100 will be right at dead-on at 200 and about six inches low at 300 yards.
This omits magnums, hot-shot .22 centerfires and cartridges in the .30-30 class.
Brian Pfleuger
Moderator Emeritus
Your .30-06 would be in the vicinity of Art's description.
.30-30 is a cartridge, it's like really slow .30-06
.30-30 is a cartridge, it's like really slow .30-06
RaySendero
New member
Works for me: 1/2" low at 25 yards in on paper at 100 yards.
Brian Pfleuger
Moderator Emeritus
Well, theoretically, but I've never thought it wise to sight in high-powered rifles at short range.
First, a tiny variance at 25 yards is QUADRUPLED at 100 and 10 TIMES worse at 250 yards. Errors are MUCH easier to see as distance increases. Getting on paper at 25 is one thing. "Sighting in" is another. Every gun I own will shoot one ragged hole at 25 yards.... it tells me nothing.
Second, it would be irresponsible to sight in a firearm at 25 yards and then try to shoot an animal at 100 yards or farther, for the reasons I stated above. So, even if you sight at 25, you're going to have to shoot at 100 anyway and almost certainly make adjustments, so why not just sight in at 100?
Third, you simply aren't likely to hit what you're shooting at, at longer ranges, unless you've actually put bullets there before. It's downright unethical to shoot at animals without verifying sights at the given distance, and just plain frustrating trying to hit paper. In other words, even if you sight for 25 and then try to hit paper at 200, you're going to have to make changes, so you might as well sight the gun at whatever practical range you have available.... because you're going to end up doing it anyway.
First, a tiny variance at 25 yards is QUADRUPLED at 100 and 10 TIMES worse at 250 yards. Errors are MUCH easier to see as distance increases. Getting on paper at 25 is one thing. "Sighting in" is another. Every gun I own will shoot one ragged hole at 25 yards.... it tells me nothing.
Second, it would be irresponsible to sight in a firearm at 25 yards and then try to shoot an animal at 100 yards or farther, for the reasons I stated above. So, even if you sight at 25, you're going to have to shoot at 100 anyway and almost certainly make adjustments, so why not just sight in at 100?
Third, you simply aren't likely to hit what you're shooting at, at longer ranges, unless you've actually put bullets there before. It's downright unethical to shoot at animals without verifying sights at the given distance, and just plain frustrating trying to hit paper. In other words, even if you sight for 25 and then try to hit paper at 200, you're going to have to make changes, so you might as well sight the gun at whatever practical range you have available.... because you're going to end up doing it anyway.
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Tried & true for me
Years ago a gunsmith told me that for most 30-06 rifles and ammo the point of impact at 50 yds would be the same as 100 yds.
I have tested it and checked out trajectory calculators and it has worked for me. I usually sight in a 1-1.5 inches high at 50 yds, check it at 100 yds. According to the ballistic calculators that should put it about 2" low at 200 yds.
Since deer have about a 6" kill zone, I am good out to 200 yds and that is about as far as I can take a shot at a deer in the area I hunt.
Years ago a gunsmith told me that for most 30-06 rifles and ammo the point of impact at 50 yds would be the same as 100 yds.
I have tested it and checked out trajectory calculators and it has worked for me. I usually sight in a 1-1.5 inches high at 50 yds, check it at 100 yds. According to the ballistic calculators that should put it about 2" low at 200 yds.
Since deer have about a 6" kill zone, I am good out to 200 yds and that is about as far as I can take a shot at a deer in the area I hunt.
RaySendero
New member
killa,
If your asking me - You got to get on paper at 100 yards first!
I've seen many bore sighted rifles that would not hit a target at 100 yards to even get started sighting-in! So...I start at 25 then move to 100 without wasteing a shot!
Brian Pfleuger
Moderator Emeritus
I agree, but I've never started at 25. I typically start at 50. I bore-sight my rifles.... literally. I look down the bore and move the scope to match. I always shoot at 50 first, but the technique has never failed to put me on paper at 100. I should have mentioned that you'd likely need at least one shot at closer range, but I'd still never "sight-in" at less than 100.
TargetTerror
New member
Why bother with rough figures when you can get the precise figures so easily? Go to this link:
http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
measure your scope height from the bore (or just estimate it at ~1.5 inches, which is usually pretty close), plug in your bullet and velocity and you'll know your trajectory.
http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi
measure your scope height from the bore (or just estimate it at ~1.5 inches, which is usually pretty close), plug in your bullet and velocity and you'll know your trajectory.
Art Eatman
Staff in Memoriam
I use the 25-yard target when beginning the sight-in with a newly-mounted scope, after bore-sighting. It usually takes maybe three or at most four shots to get dead-center at 25. After that, it's my usual deal as I said in my first post. I generally need two to three three-shot groups to dial in the group center for my usual two inches high at 100 yards. Been doing it that way for forty forevers with Lord knows how many different rifles through the decades.
Shell, the muzzle velocity of a .30-30 is around 2,200 to 2,300 ft/sec, which is why it doesn't fit in with what I've called the generic "deer cartridges". Sure, the .30-30 is a deer cartridge, but in a different class from the faster stuff. The others I mentioned shoot a tad flatter.
On my pet hunting rifle, I always zero my '06 for 200 yards with the 150-grain Sierra. That puts me around six inches low at 300, which is likely 90+% of all hunting shots. I do the same for my 7mm08 and my .243. At least, I've only shot two bucks out past 200 out of maybe 50 total. One at 350 and one at 450. Once sighted in, I don't change the settings.
Prairie dogs, I've regularly gone to 300 and a few at 400. But that's not really hunting. Mostly, just target practice.
Shell, the muzzle velocity of a .30-30 is around 2,200 to 2,300 ft/sec, which is why it doesn't fit in with what I've called the generic "deer cartridges". Sure, the .30-30 is a deer cartridge, but in a different class from the faster stuff. The others I mentioned shoot a tad flatter.
On my pet hunting rifle, I always zero my '06 for 200 yards with the 150-grain Sierra. That puts me around six inches low at 300, which is likely 90+% of all hunting shots. I do the same for my 7mm08 and my .243. At least, I've only shot two bucks out past 200 out of maybe 50 total. One at 350 and one at 450. Once sighted in, I don't change the settings.
Prairie dogs, I've regularly gone to 300 and a few at 400. But that's not really hunting. Mostly, just target practice.
38superhero
New member
I'm with ART...err not literally just i concur with sighting in 2in high at 100 yds...
Art Eatman
Staff in Memoriam
Aw, it's just a lazy man's way of avoiding thinking. "Point it and pull; Hell ain't half-full."
"Point it and pull; Hell ain't half-full."RaySendero
New member
TT,
I use that site for all my rifles - But those are still "rough" numbers. Even with the sight measurement, a chronoed velocity and a manuf's BC, You still need to shoot'em all the way out to your max hunt range.
I find the JBM trajectory is perfect for only one of my rifles - It shoots to the JBM trajectory out to 400 yards +/- 1". The others are off some and need to be shot at several distances.
Brian Pfleuger
Moderator Emeritus
I also use JBM ballistics but have never found it exactly accurate. Real bullets fly flatter than JBM thinks they should. One day, I switched the drag function to G2 and now it matches the real world almost perfectly.
But, as Ray said, you can never count on it. You have to put bullets on paper.
But, as Ray said, you can never count on it. You have to put bullets on paper.
RaySendero
New member
THX for the tip - I'll try that G2