Question for you rifle guys

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tnieto2004

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The other day I was sighting in a rifle in .223 .. I bore sighted it and shot at 25 yards just to make sure it was close.. It was dead on at 25 yards when I had to leave to be somewhere .. I didn't get to shoot it at 100 yards.. If I am dead on at 25 yards, How off will I be at 100 yards? Thanks..
 
Depends on a lot of factors, but the most important one is height of your sights above the bore. What kind of rifle is it? Irons or scope? And how far above the bore line are the sights (center of scope or top of front post)?
 
Another issue is the tiniest error at 25 yards will get magnified at 100 yards.

There's no way you can rely on a 25 yard zero unless that's the only range you shoot at or less.
 
It is a scope .. I had just put a new scope on it so I was making sure it would be close at the 25 yards when I had to go.. I haven't measured the height above the bore.. the scope sits fairly close to the bore though..
 
Using the Remington Shoot! calculator, 1.5" sight height, 55 gr bullet w/BC of .202 and 3240fps MV:

a 25 yd zero will also give you a dead on zero at 260 yd.
You should hit about 3.1" high at 100.
 
If you have a 25-yard zero, the point of impact will be approximately 2-2.2x higher at 100 yards than the sight over bore distance, for a typical 223 load.
 
Well, even the lowest mounts still put the sight plane of a scope quite a ways above the bore. That will result in significant difference between 25 and 100 yard impact points, because the bullet is actually on a fairly steep climbing trajectory to hit the aiming point at 25 yards.

Assuming a typical 55 grain bullet moving at around 3,100 fps, and a scope centerline that is 1.5" above the bore, a 25 yard zero equates to a POI at 100 yards that is 3.0 inches above your aiming point. If your scope is 2.5" above the bore, the POI will be even higher -- about 5.7 inches above POA at 100 yards.
 
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