Home Forums Hunting & Shooting Ask The Gunwriters 25 yard sight in ?

If you sight in at 200 yards with most rifles, your first zero will be somewhere between 23 and 27 yards, depending on the muzzle velocity. So 25 yards is a good place to start.

Marlin put out a little sliding calculator thing with the trajectories of a bunch of loads, from .22 LR to .30-06, with the first zero set to 25 yards with iron sights and with a scope sight.

OK. I'm confused. Lee24 says a 25 yard zero is good for a 200 yard sight in or there abouts and others say it is closer to a 400 yard zero. Then I had my old 30-06 shooting 8" high at 100 yards after a 25 yard zero. Since the books generally say a 180g bullet fired from a 30-06 at 2700 fps will be about 8" low at 300 yards with a 2" high zero at 100 yards, what would 8" high at 100 yards garner me. Personally I'm thinking I would miss everything I would attempt to shoot at.

Now it may have already been said, but I feel it would be better to sight in at 100 or whatever farther distance than check it at 25 or 50 to determine where the bullet will hit at thoses ranges. This is in case you get to a place that doesn't have a 100 yards or longer range and you have to recheck your sight in. To be honest I have never had to do this, but it would seem like the thing to do. I am sure, however, that someone has a better idea.

The only thing I use 25 yards for (speaking of biggame hunting rifles) is to get on paper before going to 100 and farther.

If I were you, I'd be listening to John Barsness, aka Mule Deer, rather than Lee24. Lee24 might have invented the 25 yard zero, but that still doesn't make it a good technique.

That's why you are confused. Put him on ignore and enjoy the rest.

Something just doesn't seem right with those figures..If you took the same rifle/load combination, and zero'd it 2" high at 100 yards, those figures indicate it would be 5" low at 25yards..

What rifle and load was it?

My ballistics program shows with a 2800 fps .308 165 gr. Speer BT a 25 yard zero will be about 2.75" high at 100 yards.

That's with a scope 1.5" above bore.

Those are certainly the ball park sort of figures I'd expect and what I've expirenced..

When mounting a new scope, I usually bore sight and then shoot at 20-25 yards, and then move out to 100 to 150 yards to confirm zero..

The 25 yd zero got a lot more popular with the AR-15 crowd, IBZ or something like that. Really the 25 yd zero does help to tell which direction the rifle is shooting.....

I guess I should have used an emoticon because I was being facetious in the first paragragh.

I usually take JB's advise and experiance seriousely. So far that which I have used has worked.

If you zero a .30-06 with a normal load of a 165-gr bullet at 25 yards with iron signts, it will be on again at 150 yards and about 2.25 inches low at 200.

If you zero the scope, set 1.5 inches high, at 25 yards, you will be about 2.25 inches high at 100 yards and on again about 215 yards.

I ain't guessing here, folks.

I have been doing this for more than 45 years.
Lots of my rifles are set up with iron sights and scope sights.
I don't set the first zero at 25 yards. I use a different method, but I know exactly how everything from my .22, to my .30-30, my .308, to my .270, works with a 25-yard zero, because I have tried it all, a long time ago.

But those of you who don't own a rifle, or don't know how to sight one in, can play with your favorite ballistics program on the internet. If your program, or favorite gun writer, is much off from my real world numbers, you'd be wise to quit believing them.

Pete,

You are getting confused by math. An inch at 100 yards is equivalent to 1/4" at 25. A rifle 7" high at 100 should be sighted-in 1.75" low at 25 to be dead-on at 100.

In reality there will even be some variation, because of recoil, barrel "flip" and other factors.

The rifle in question was a .375 H&H Ruger No. 1.

Gene L,

One of the problems is that very few scopes are only 1.5" over the bore anymore. The other problem is recoil and barrel flip, as mentioned in my previous post.

In other words, there is often a difference between computer predictions and reality

I have seen the same thing too in my rifles (not been to Africa yet, so I can't comment on PH's). Some of my rifles when sighted in at 25 yards are anywhere from 5 to 8 inches high at 100. The higher the scope mounts, the worse it becomes. Given this and your comments that "that very few scopes are only 1.5" over the bore anymore" I ran some calculations on my RCBS ballistics program. I just picked a 150 gr Hornady .308 at 2800 fps. Setting the sight height to 1.5 inches, the program predicts 2.6 inches high at 100 yards for a 25 yard zero. If you set the sight height to 3 inches, the program predicts 7 inches high at 100 yards with a 25 yard zero. A 2.5 inch height yields 5.5 inches high at 100, while a 2.0 inch height yields 4 inches high at 100. I decided to plot sight height versus predicted 100 yard point of impact.
As you can see, the relationship is linear.


As you might expect, the predicted POI will vary as a function of velocity. While there may be some minor error involved in the predicted POI (+- a few tenths), this graph largely reflects my experiences.

AFTER you get your rifle sight in at 100, 200, or whatever, THEN shoot it at 25 paces. Remember or record where it hits. You now have an easy way to check in the field to see if it is still on.

Bruce

Nope, not thinking of that aspect at all...

If a rifle is dead on at 25 yards, but is + 7" at 100yards, if we lower the point of impact at 100 yards by 5", to give a more reasonable +2" zero, it would also lower the point of impact at 25yards, to approx -5" ??



Agreed...

The entire trajectory does not move down as a unit. Think of the trajectory as pivoting at the muzzle. A five inch change at 100 yards will be a much smaller change at 25 yards.

Bruce

I agree completely. As I argued earlier in this thread, producing your own trajectory tables (as opposed to solely relying on calculations) is the most prudent approach. With the plot that I attached, I'm attempting to stress the importance of sight height on a 25 vs. 100 yard zero.

If you go to Hornady.com. Go into ballistic tables. You have to know velocity, ballistic coeffecient, and bullet. You can adjust your sight in to whatever your conditions will be.

And you also need to know your sight height.