dumb sighting in question

[green_MTman]

before all of you westerners laugh i live in vermont and grew up in massachusetts.so long range shooting has been a non issue.

they say its wrong to sight in at fifty because you will be high at 100.but 55,65 yds is an average shot where i hunt.but if i got a shot at 100 or 150
how high would i be?

they say if you sight in a flat shooting rifle getting about 2,800fps second at 25 yards you will be dead even at 250.
but how high would you be in the inbetween distances

they say if you sight in an inch and 1/2 high at 100 you will be 3 inches low at 300.
is that true?

i am shooting a 6.5-55 SE using 120,130,140 gr bullets depending.but why dont we say the 120gr because that is what i use for deer.bear and moose are always inside 75 yards anyway

i moved last year and my old rifle range is now an hour a away and im not going to renew my membership there.and i dont shoot long ranges much anyway.this year i may just go into the woods a sight in at 25 or 50 yards.
last black bear season i saw a doe about 300 yards away.it was a doe and is was not even deer season but it shows in the east you may stumble on the ocational long shot.

[Sierra280]

All those numbers you mention will vary with bullet weight and velocity.

I always do the 25yd sight in. If the gun is only going to be used for hunting, sighting in at 25yd will keep you well within the heart/lung area of any large game animal out to 250-300yd. Of course, after sighting in, take some 200-300 yd shots, ballistics calculators are really only a general guide, you have to get some real world data for bullet trajectories with your specific gun/ammo combo.

Jack O'Connor always did the 25yd sight in, he knew a thing or two about hunting.

[green_MTman]

i would have to look up my journal.the deer i took two years ago 6.5 mauser 120 sierra pro hunter i think about 2850 but i would have to get my journal.i thought as well as you said that i would within the vitals at 300.

it was a good load. nosler brass, federal 210 match primers,varget powder.
i wont mention powder charge online without double checking my journal as not give advice that could be unsafe.

[PetahW]

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I, too, hunt Northern New England - and know that large fields and/or power line clearcuts can offer shots longer than in most N.E. hunting areas.

I carefully sight in at a measured 25yds, then check the zero @ 100yds - A 100yd zero 1" high should make you good to go to about 300yds.

The 300yd PBR (Point-Blank-Range) means your bullet should be no more than 3" (or so) higher or lower than your line-of-sight out to that distance - which means you can simply "hold on hair" w/o thinking about the trajectory.


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[Brian Pfleuger]

If you're going to be shooting 50-75 yards, it really doesn't make the slightest difference what range you pick for zero. You're going to be within an inch anyway.

However, if this is what they say:

they say its wrong to sight in at fifty because you will be high at 100.


they say if you sight in a flat shooting rifle getting about 2,800fps second at 25 yards you will be dead even at 250.

They are very confused. Being zeroed at 50 will put your bullet lower at 100 than being zeroed at 25 will.

Using JBM Ballistics Calculator and inputting a 129gr SST at 2,800 fps, a 25 yard (technically 24) zero will indeed be roughly zero again at 250 yards. However, it will also be 3" high at 100 yards. At your range of 50-75 yards, it's 1.4" to 2.3" high.

Zeroed at 50, you're going to be about 0.3 inches high at 75, peak at 0.4" high around 88 and be 0.3" again around 100, but you're going to to be almost 7" low at 250.

Ultimately, there's no sense in worrying about where you're shooting at 250 (or even 100) yards if you can't see past 100.

[Art Eatman]

I've messed with bunches of scope sighted bolt-actions in all sorts of calibers. A simple rule of thumb for most "deer cartridges" with a muzzle velocity above 2,500 ft/sec on up to maybe 3,000 is that dead-on at 25 yards is commonly about three inches high at 100 yards.

Two inches high at 100 is right at dead on at 200. It will be roughly six inches low at 300, give or take an inch.

I've always sighted in for a 200-yard zero. I've killed deer anywhere from 25 yards to 450. It never seemed very difficult. Since most of my kills were inside of 200 yards, I didn't have to think. Just point it and pull; Hell ain't half-full.

[jmr40]

With most modern centerfire rounds a 100 yard zero is fine. 50 yards is too close except for rounds like 44 mag, maybe 30-30. You will end up several inches high at 100 yards. With my rifles with a 100 yard zero at 50 yards I'm about 1/2 low. At about 115-120 yards I'll be about 1/2" high. By the time I'm out to about 130-140 yards I'm 1/2" low again. If I need to shoot farther I'm only about 2" low at 200 yards and around 8-10" low at 300 yards. No holdover needed at 200 and compensating for 8-10" at 300 isn't that big of a deal.

Even out west 150 yards or so would be where most shots are taken, although the odds are better of longer shots. I like the idea of not being more than 1" higher or lower than where my crosshairs are setting. This is I believe the best option for shooting through holes in thick brush even at close range.

For guys who regularly shoot past 300 yards having a 200 or 300 yard zero does make sense. It means less hold over out at 400-600 yards. But a 300 yard zero means you are 4-5" high at closer ranges where most shots are actually taken. It's just easier and more natural to hold 4-5" over an animal at 300 yards, than to remember to hold 4-5" low at 100.

[green_MTman]

trajectory not something i have ever understood.i have always wondered why the shorter you sight it in the less it drops down range.trajectory is the only part of bullistics ive never understood well.
but sounds like if i sight in at 25 it will be even at 250 and only 3 inches high at 100.
my scope is to cheap to have much vision past 200 and some change anyway.

[Brian Pfleuger]

In simple (slightly over-simple) terms, the reason a bullet "drops less" at long range if you zero at a closer distance is because you're firing the bullet at a higher angle.

It doesn't "drop less", it goes higher so it takes longer to come back down.

All objects drop the same amount in the same time. (Ignoring air resistance).

When you sight a gun at 25 yards instead of 50, you are using a tiny bit of its velocity to give it additional height, so it's essentially falling from a different height.

There's physics involved and I've burned all my physics give-a-damn in another thread tonight so I'll just hope that sort of correct word picture does it for you.

[lonniemike]

Until you figure out a better zero, the 25 yard/meter zero will serve you well with about any firearm you choose and especially with the 6.5X55.Best

[jimbob86]

....

Until you actually put some (more than "a bunch, at that) live rounds on a practice target at 200 or even 300, such that you can be reasonably sure of a hit, please don't take shots at game that far because "they" said if you zeroed at 25, you'd be good at 250 or whatever...... when your shot goes poorly, "they" won't be there to answer for their advice..... and you won't have the benefit of experience to figure out what you may have done wrong.....

" "They"?!? told you to? .... So "They" is a Sergeant now, givin' orders? Well, I'm the First Sergeant HERE, now you go get me "Sergeant They", bring him HERE. Bring HIM raught HERE (points to the ground at his feet). You got 5 minutes. Go."- First Sergeant Cook, US Army, Peden Barracks, Federal Republic of Germany

[green_MTman]

thank you for all the helpfull responses.i have always been good with bullistics but not trajectory.
i would agree with the person who said one should not put a beautifull deer at risk of being only wounded unless one practices at the long ranges first.

[Mobuck]

Nothing is gained and you handicap yourself by using a sightin distance shorter than what is considered "optimum". For most hunters who don't shoot much, adjusting for 1-1.5" high @ 100 yards will give a suitable bullet strike within the capability of the cartridge. In the past, many suggested a 2.5-3" high @ 100 yards sightin. This works for me BUT I found it confused many people for whom I mounted and sighted in optics. Not knowing much about judging distance, they started "holding over" at about the 250 yard range and consequently shot over most critters.
The only rifles I sight POA=POI @ 100 yards are those for the Grandkids. I don't let them shoot much over that distance at this time and I want the bullet to stay as close as possible to the crosshairs.

[emcon5]

What you really should do is run some numbers for your rifle and load, and see what comes out the other end.

http://www.jbmballistics.com/ballist...culators.shtml

Sight height matters, for the ranges you are talking about, altitude probably not enough to worry about.

Something important though, is to reality check your load at longer range.

If the calculators say a 25 yd zero will be X at 100 and Y at 150, go fire a shot and confirm it.

[gk1]

When you sight in, you're adjusting the sights to point the barrel slightly up, so that as the bullet leaves the barrel it will cross the line of sight at 2 points, one as it is approaching its peak and one as it arcs back toward the earth. Between those points, it will be above the line of sight, and before and after those two points it will be below.

If you select 25 yards as a sight-in range, that will be the first of those points; the bullet will continue its path upward (due to the barrel being pointed slightly above parallel to the ground and line of sight) until the bullet no longer has enough velocity to overcome the constant pull of gravity, and passes the top of the arc of its trajectory, when it begins approaching the line of sight again.

Somewhere around 200-250 yards (rough guess for your cartridge) the trajectory of the bullet will cross the line of sight the second time, so that your "25 yard zero" is also a "225(ish) yard zero". Incidentally, the point of impact will also be 2-3 inches high at 100 yards and 3 inches low at around 275 yards.

Hopefully this image will help illustrate the concept:

[Sea Buck]

Sierra280; What is the Jack O'connor 25 yard sight in? I'm not famliar with this although I do know of (genflect) Jack O'Connor.Is it more than a simple 25 yd sight in?

[emcon5]

What is the Jack O'connor 25 yard sight in?

Been a while since I read it, but it is the general theory that for most rifles, if you zero at 25 yards you will be within ±2-3" out to 300 yds.

While technically true (again, generally speaking). This may have made sense as a rule of thumb when he wrote it (and he died in 1978, so it was a while ago), with the availability of ballistics data\calculators, chronographs, etc, there is no reason not to work out what your rifle does.

You can certainly use 25 yards as a starting point, but I would never actually zero my rifle there. Probably a better way would be to decide where you want the rifle zeroed, say 200 yards, then punch the numbers into a ballistics program and figure out where it will be hitting at 25 to reach your desired zero, then reality check it at your full zero distance.

For example, my rifle with a 200 yard zero, JBM says it would be 1/2" low at 25 yards, and 1.5" high at 100. I have confirmed at 100, and it is pretty close.

[SIGSHR]

In BCT in 1967 we zeroed our M-14s on the 1000 Inch Range, I recall our being told the trajectory of the 7.62 was such that we would be good out to 300 yards or so.

[Sierra280]

It can be found in "The Rifle Book" published in 1949. In the chapter 'Trajectory and Sighting-In' he goes over the details. But basically what everyone is saying; because if the trajectory a bullet takes, sighting in a 25yds will put you right on at 200-250 yds.

[603Country]

With a new scope on a rifle, I'll do a rough zero at 25 and then sight it in at 100 or sometimes an inch high at 100. Personally, I would not dream of doing a 25 yard sight-in and then going hunting. I just wouldn't do it. And if you think a 25 yard sight-in is Ok, don't come hunt with me because I'm not tracking your wounded animal.

The better you are with your gun, the worse tracker you can afford to be.

[Art Eatman]

I've had several sub-MOA rifles be dead-on at 25 yards and for some unknown reason be two or three inches to the side at 100 yards. Not always, but often enough that 25 yards is merely to ensure being on the paper at 100.

[Sierra280]

Vertical dispersion of shots is (mostly) due to variations in muzzle velocity or inconsistency in distance, or range estimation err. Horizontal shot dispersion is almost entirely due to wind (or a hardware issue).

Keep in mind anything that happens at 25yds will be EIGHT TIMES GREATER AT 200yds! Hence the reason a rifle should actually be tested at said range.

[jimbob86]

anything that happens at 25yds

will be hard to tell a whole lot about without calipers and something to find the center of the holes

[Sierra280]

If the 25yd five shot group is so tight you need calipers to measure it then you will be fine. I'll do some simple math for everyone. 1/4 group at 25yds= 2" group at 200. 3/8in group = 3 in at 200 1/2 in group = 4in at 200yds.

All well within the vital area of a large game animal.

But as everyone keeps repeating, actually test your shots at the distance you plan on shooting.

[603Country]

If you are going to shoot at 100 yards, sight it in at 100 yards. A 25 yard sight-in isn't always going to be indicative of what group you'll get at 100. I've seen that too many times with rifles. It ought to print well at 100, but it doesn't. Why? Well I guess we can discuss it forever, but back to the point that matters. Sight it in for a 100 if you are going to shoot at 100.

Of course, you don't have to listen to me (and some of the others), but remember this when the big buck runs off. We told ya....