sighting in at 25 yards for 100 yard shots


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p89cajun
January 22, 2007, 12:14 PM
The outdoor range I frequent is a good ways away and I heard it is just one big mudpit due to all the rain but I need to sight my rifle in so I am going to have to go to the indoor range. The only problem is our indoor range is only 25 yards. I know there is a chart for if your shooting (blank) round at 25 yards you should hit (blank) inches high to be on at 100. Where can I find this chart. I know it isn't quite like shooting at the full distance but it will have to do.

P.S. I shoot a 180 grain 300 mag. If anybody knows the numbers I would greatly apreciate it.

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nitesite
January 22, 2007, 12:20 PM
I'd like to get you some useful info, but without knowing how far your scope is mounted above your bore line, it's almost impossible to come close.

p89cajun
January 22, 2007, 12:22 PM
So how my scope is mounted will play a part. I thought it was just bullet drop.

mainmech48
January 22, 2007, 12:44 PM
Using published ballistic data tables for a factory load, assuming comparable barrel length, etc., or one of the commercial programs one could likely get 'in the ballpark' by determining how much the bullet should theoretically rise above LOS at 25 yds with a 100 yd 'zero' and put the group center there.

I wouldn't take it hunting just then, but it'd likely save you some time and a goodly amount of ammo when you finally got to shoot-to-verify at 100 yds. Bear in mind that it's a large ballpark where other variables can come into play, but at least you should be on one base or another.

Just out of curiousity, what in the world could be so urgent that you'd be willing to touch-off a series of .300 Win. Mags indoors, even assuming a range where they'd let you? Probably ring your ears off right through several layers of plugs and muffs and get you into the Very Bad Graces of numerous strangers, at the very least.

M2 Carbine
January 22, 2007, 12:45 PM
There's little bullet drop at 25 yards. So at 25 yards the bullet should hit lower than your crosshairs close in.

As strickly a rule of thumb, depending on the gun, I have the bullet hit 1/4-1/2 higher than the distance between the X hairs and bore.

In other words if the scope X hairs are 2 inches above the bore I sight in to hit 1 3/4 inches low at 17-25 yards.

This usually gets me within a foot of center at 100 yards.

But it all depends on the rifle and ammo used.

sumpnz
January 22, 2007, 12:50 PM
Most people I know shoot rifles at 25 yards for the sole purpose of getting the sights adjusted enough to ensure they're at least on the paper at 100 yards. If I'm mounting a new scope I first do a poor mans bore sight (place the gun in a steady rest, remove bolt, look down the bore and center on the target, then adjust scope to be centered on the target), then I fire a shot and if it's pretty close (within an inch or two) to the center of the target I'm done. Otherwise I adjust the scope and fire another shot. Usually that gets me close enough. If I was being a dufus and forgot to quadruple the clicks to adjust I might have to take a third shot. After that it's off to the 100 yard line for the real sight in.

BTW, most high-power rifles will shoot 2-3" higher at 100 yards than at 25, assuming the scope centerline is 1.5" over the bore centerline.

Jackal
January 22, 2007, 12:55 PM
As stated above, the distance between the bore centerline and the scope centerline is extremely important. I'm gonna take a guess and say that the cartridge has a muzzle velocity of 3000fps and your using spitzer shape bullets. Also, another guess, that the scope is about 2 inches above bore centerline. If you zero a half inch low at 25 yards, you should be flat out to 250 yards, with only 1.3 inches of drop. This is a zero of 40 yards, ideal for my above guesses. With this calculation, your only 17" low at 400 yards. However, remember that this is rough estimation, since I dont know the exact numbers.

MrDig
January 22, 2007, 01:05 PM
Scope height from the Bbl is less relevant in this discussion than what round, and how long the Bbl is.
ie
24 inch Test Barrel 1.5 inch sight height
Federal .243 Win. 100gr soft point. trajectory in inches is as follows:
25yds 50 75 100 125 150 175 200
-0.7in -0.2 0.0 Zero -0.3 -1.0 -2. -3.3

So at a 25 yard range shoot -0.7 inches low to achieve a 100 yard zero
This is data from the Federal Ballistics Program I downloaded from Federal Ammo.

rangerruck
January 22, 2007, 09:16 PM
so you do have a scope? Let us assume that it's centerline is about 1.5 inches above the center line of the bore of the rifle. lets also assume you are firing centerfire. At 25 yds, I would be shooting 1/2 inch low at 25 yds, that means in that short a distance, your bullet has risen approximately 1 inch that quick.
Depending on bullet speed , this will proly put your shot 1/2 inch high at 100 yds.

____hoot____
January 23, 2007, 08:57 PM
It cost me two deer believeing that old 25 yard dead-on, 3 inches high at 100, on again at 225 site-in theory. Maybe it works for low speed loads with low scope mounting. Was useing new "light magnum" 30-06 bt 165 grain hot loads and a new big, for me, 6x42 scope. Missed a buck clean at 250 yards and the next day blew hair off one's back at 100 yards. Put a target out at the location where the buck was at 250 yards and found I was shooting eight inches high there!!! Yipes!

Dave R
January 23, 2007, 09:58 PM
FWIW, I just went through this exercise. Got a new scope mount for my CETME ($26, delivered!) and threw an old 3X9 scope on it. Temps and wind were awful, so I took it to the indoor, 25 yard range and did it the hard way.

I shot another rifle whose zero I knew to be good (and with similar bore/scope distance) at the 25 yard target. Impact was about 1 3/4 inches low. Sighted the CETME to the same POA.

A few days later, I went to the outdoor range. First rounds at 100 yards were right on the money.

Sunray
January 23, 2007, 10:09 PM
Firing a .300 mag inside will have dust falling from the ceiling for about a week. You'd best make sure the back stop will not be damaged by it too. Plus warn anybody else there when you're about to shoot.
You'd be better off getting some rubber boots and wade out to 100. Shooting a .300 mag at 25 yards to try and sight in is a waste of time and ammo.

rangerruck
January 23, 2007, 10:19 PM
these dudes are all correct, I was assuming a mild mannered round, if you are firing a round that is doing over 3000 fps, and it is heavier than say 120 grains, then that thing will really climb the ladder so to speak, to zero at 25 yds. If it is a 308, it is still pretty fast for a heavy bullet, so if your scope line is 1.5 inch above bore line, i would look for a 1 to 1.25 inch low at 25. If you are two inches above, look for 1.5 inches low at 25.

rockstar.esq
January 24, 2007, 12:47 AM
Truly don't mean to be disrespectfull but I just can't understand why you're worried about being "spot on" at 100 if you're shooting at 25. Personally I'd just sight in at 25 and figure that there's an inch or two of tweaking to be done once you get a shot at 100 yds. Most of the tables and charts I've used are close however I like to test my accuracy at all ranges in question.

Seriously I find WAY more shooters have canted scope reticles on their "dialed in" rig which sort of defeats the purpose of a perfectly calibrated set up.

Plus lots of hunters set themselves up with a 250yd zero figuring that if the Ungulate is within 300yds or so they can just place the reticle in the center of the boiler room and count on a full freezer.

wuchak
January 24, 2007, 01:40 AM
You can get a copy of Remington's Shoot ballistics program at http://www.remington.com/products/ammunition/ballistics/remington_shoot_ballistics_software.asp

In the settings section you can set the sight height.

Once you set the zero range and target range choose Ballistic report from the Calculate menu. Your

It's fun too play around with different zero ranges to find the one that gives the max point blank range with your load for the game you're after.

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