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Re: zeroing a scope question???????

hardly said:
I'm very new to this so bear with me. I have a Browning 22-250 and have been trying to understand ballistics as it applies to setting a scope. I have a lot of people telling me to set the scope at 100 yards, but looking at ballistic charts, it seems to me that zeroing at 50 to 65 yards makes it a little high at 100 to 150 yards but better trajectory down range. Can anyone give me some insight.
hardly,

I'd say you've got the correct idea.......Think of trajectory as a baseball that you throw across the field. The trajectory is a curved path rising then falling to earth, as opposed to line-of-sight which starts out as a straight line and continues to infinity, never dropping. Let's see what this web site says about the subjest:http://members.aye.net/~bspen/ballistics.html. Here's a short note sent me a year ago.

"Sight the gun in at 25yds. dead on. Give or take variables too small to matter and you will be dead on again at 200yds. or a bit further. If you think about it, you'll understand why. The bore is below the scope right? So the bullet has to start out rising up to the line of sight of the crosshairs and it first crosses the line of sight at 25yds. It reaches maximum height above the line of sight at around 150yds. (about 2" or so) and then as it begins to slow down and gravity pulls it back to earth, it is again dead on around 200-225yds. Neat huh? You don't need more than 25yds. range to sight in, but of course, you should check it at longer range when you get a chance, but I wouldn't hesitate to go hunting with the gun sighted in at 25."

Rick Rappe 12/20/2001



savageT
 

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zeroing a scope question???????

:grin: I echo everything SavageT says and would like to add this. Make sure you understand that you must be dead on at 25yds, not even a little off because when you shoot at longer ranges to fine tune your site in, say 100 yds, the error will be magnified by 4 times or more. Also note that most scopes need 16 clicks to move 1 inch on the target at 25 yds.
Have fun shootin :D
 

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zeroing a scope question???????

Hardly,
Beware the practice of zero at 25 yd then assume you are good to go at a greater distance. Without knowing the bullet you are using, the muzzle velocity, and the distance from bore line to cross hairs it is impossible to give accurate sighting advice.
Here are some examples from the external balistics calculator in RCBS Load 2.88. Each of these are calculated from an initial zero range of 25 yds.
bullet --------------- muzzle vel -- scope ht - down range zero at -- max traj height at yd
40 gr Sierra blitz king 4200 ------- 1.8 in -------- 420 yd ----------- 8.7 in @ 248 yd

40 gr Sierra blitz king 4200 --------1.3 in -------- 345 yd -----------4.7 in @ 198 yd

69 gr Sierra MKHP --- 3200 -------- 1.8 in ------- 320 yd ----------- 5.7 in @ 320 yd

69 gr Sierra MKHP --- 3200 -------- 1.3 in ------- 245 yd -----------2.9 in @ 142 yd

These are extreme examples from each end of the 22-250 performance spectrum, but I think you can see the point I am trying to make here.
A much better practice for sighting in your rifle is: First determine how much rise above sight line you wish to deal with. This will determine the distance for which you will actually sight in the rifle.
For instance if you want 55 gr spitzer bt bullet @ 3700 fps to never be over 2.5 inches above line of sight with a scope mounted 1.5 in above bore line. RCBS Load 2.88 tells us to sight the rifle in to zero at 265 yd.
We can get an initial zero at 35 yd, then check at 100 yd. The rifle should print 1.94 in high at 100 yd. This will give us a max of 2.49 in above line of sight at 156 yd and the bullet should be 2.5 in low at 307 yd.
You still never know for sure until you actually shoot the rifle at 200 and 300 yd and compare your targets to the balistic charts.
I actually zero my 22-250 at 300 yd using the Hornady spire point 60 gr bullet at 3600 fps. I have to hold the cross hairs under the target for shots between 125 and 250 yd, but do not have much hold over until after 350 yd.
If you do not have access to a good balistics program, there is a good one available to download for free at this sight.

http://www.huntingnut.com/pointblank.html
 
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