.22LR Ballistics?

[Aguila Blanca]

I think it's time to dust off my Henry .22 lever action. I'd like to zero a cheapie scope I picked up for it, but the weather isn't very nice right about now and the indoor range where I normally shoot only goes out to 25 yards. If I wanted to use that to get as close as possible to a 50-yard zero, how high (or low) should I be hitting compared to point of aim at 25 yards?

 

[rangerruck]

a dead on zero with standard or high velocity ammo will put you about 1 inch high at fifty, assuming you mount your scope right above the bbl, not where you have a 1/2 inch of space between the bbl and the scope. Also it should be a scope with a small bell, between 32 and 40 mm. the gbigger the bell, the higher the zero will come up at 50.

 

[Aguila Blanca]

I have read and re-read this response, and I still don't understand it. I'm not asking how far off I'll be at 50 yards if I zero at 25. I want the rifle to be zeroed for 50 yards, but I have to shoot at a 25 yard facility. So, to accomplish a 50 yard zero, at 25 yards I can't be hitting point of aim, I have to be either high or low.

That's what I'm asking: Do I want to be hitting above or below point of aim, and by how much?

The rifle is a Henry .22LR lever action, and the scope is a basic rimfire scope that fits pretty close to the top of the receiver and barrel.

Thanks.

 

[ArmedBear]

If you sight in a .22LR rifle at 50 yards with a scope (nominally 1.5" above the bore), it will also be sighted-in at 25. Note that it will shoot slightly high somewhere in between, because the bullet travels in an arc that is still rising at 25 yard, but is falling at 50.

Sight it slightly high at 50 yards and it should be +/- 1" from 5 yards out to 75 yards or more.



http://www.gunsmoke.com/guns/1022/22ballistics.html

I think the best range for sighting it in is about 45 yards; if you sight it about 1.5" high at 45 yards, it gives you a good enough trajectory to hit small game out to 90 yards or so without paying any attention to elevation. But simply sighting-in at 50 yards is close enough for general purpose use unless you're going for head shots on chipmunks.

 

[Aguila Blanca]

Actually, based on that chart, it appears a 25-yard zero will put point of impact about 1/4" above point of aim at 50 yards. That's a good frame of reference. Looks like I want to set my point of impact about 1/4" below point of aim at 25 yards.

Thank you.

 

[ArmedBear]

Realistically, your groups are going to larger than 1/4" at 25 yards. Good luck determining if you're 1/4" high or not.

In real practice, with a lever action, I'd just sight it in at 50, do 10 or 20 test shots at 25 to make sure it's not way off, and call the job done.

 

[grimjaw]

I sighted my last .22 in so that POI was about 1.5" above POA at 25 yards. At 50 yards, POI is about 2" above POA.

jmm

 

[Aguila Blanca]

In real practice, with a lever action, I'd just sight it in at 50, do 10 or 20 test shots at 25 to make sure it's not way off, and call the job done.

?????

I want the rifle to be zeroed for 50 yards, but I have to shoot at a 25 yard facility.

 

[Chuck Dye]

Go to the Norma Ballistics site and use the "Define your own bullet" function. Drag the various sliders to suit your purposes. You may need to minimize your tray to view all of the muzzle velocity bar. The program will put you very close. Naturally, it would be best to check at an actual 50 yards.

In the ammo library I have, the .22LR sub-40 grain hollow points have B.C.s averaging 0.120, σ=0.011. the 40 grain solids’ B.C. averages 0.144, σ=0.014. Your ammo box should give you a nominal muzzle velocity.

 

[Picher]

If you want to make a 1/4" change at 50 yards but are sighting in at 25 yards, you only have to make 1/2 the correction, or 1/8" to move the bullet impact 1/4" at 50.

You have to remember angular deviation. One-half minute of angle is approximately 1/2" at 100 yards, 1/4" at 50, 1/8" at 25, etc.

Picher

 

[Aguila Blanca]

If you want to make a 1/4" change at 50 yards but are sighting in at 25 yards, you only have to make 1/2 the correction, or 1/8" to move the bullet impact 1/4" at 50.

You have to remember angular deviation. One-half minute of angle is approximately 1/2" at 100 yards, 1/4" at 50, 1/8" at 25, etc.

Thanks. I was a math and engineering major. I know about geometry.

Your example assumes that the bullet travels straight all the way to 100 yards. Take a look at the chart posted by ArmedBear and you'll see why doubling (or halving) the discrepancy is irrelevent to what I need to accomplish.

 

[rangerruck]

i see what you are asking now, the missing link is the velocity of your ammo, but if you are somewhere between say 1/4 to 1/2 low at 25 , this should put you near right on at 50 yds.