25yd zero...

[gedenke]

I used to think that a 100yd zero was the norm for hunting/plinking rifles(excluding smaller calibers for this discussion). But after talking to a few guys behind the counter at my local gun shops, and playing around with Remington's "Shoot!" software, I'm beginning to think that maybe a 25ys zero would work better. For now I'm shooting a .30-06 in 150gr (deer) and 180 gr (elk), but later I'm buying either a .308 or an -06. What do you guys think? About the 25yd zero that is.

Oh, and one more thing, I'm in SW Oregon and most of our hunting areas are pretty brushy, with most shots being 100yds or less, no more than 200.

On a side note, anybody play with the "Shoot!" software? It's kinda cool.

[Scorch]

I tried the Shoot! software, but then removed it. It works OK, but just OK. 25 yds won't tell you where you are actually hitting at 100 yds, and any small inaccuracies at 25 yds become bigger inaccuracies at 100 yds. Zero your rifle at 100.

[taylorce1]

Would you want to trust a 200 yard shot to a 25 yard zero. If my math is correct if you are shooting a 1" group at 25 yards that group will possibly open up to 8+" at 200 yards. To get a sub MOA rifle at 25 yards your groups would have to be smaller than 1/4" again if my math is correct.

The real problem I have with zeros at short ranges is my mistakes that I'm making don't always show up. If I'm making a mistake in my technique I want to see it and it might take 100 yards for it to show up. I hand load as well and I've had bullets that keyhole, I don't know if they would be doing that at 25 yards all the time.

The only thing I zero at less than 100 yd/m is my M16 in the Army. That is done at 25m and the target I shoot is supposed to represent a 300m target. In theory I should be zeroed at 300m, but why do I still miss that target sometimes. Again I say this is because my mistakes are not showing up at 25m.

What ballistics software says and what we accomplish at the bench are usually not the same. 25 yard zero is fine for small game with a .22 lr but for larger game I like to be accurate out as far as possible. I think 100 yards is a good benchmark to test skill by, but 200 yards and beyond on paper becomes humbling real quick.

[biglabsrule]

Hey thanks for the software, I really didn't want to buy any and it works reasonably well for my purposes. Only has remington ammo but you can find ammo prety close to other brands....

not sure about 25yrd zero, maybe 50 or 75 for conditions that are realy brushy(like I have it in upstate NY), I don't think it matters as much as people think, 3inch groups at 100 would even work fine on deer in my area, I hear people even use sks's in some areas:barf: but suppose you don't really need to have to much accuracy on a deer at 30 yards(that's how far 80% of the shots are in my area), I'll be sighting mine in almost dead on at 50...

[Zombie Steve]

I like the Shoot! software. Try and find the "Optimize Load" feature. You'll wind up with something like a 230yard zero. Pull up the "graph trajectory" feature, and you'll see where it's zeroed inside that... roughly 25 yards. I use 168's though and I'm shooting at 6,000 feet above sea level - your mileage may vary.

Like you said, it will get you in the ballpark. Only one way to be sure.

[Art Eatman]

For a 150-grain '06, dead-on at 25 is around two to three inches high at 100. Two inches high at 100 is dead-on at 200, as near as makes no nevermind, and about six inches low at 300.

For deer hunting then, anything inside of 250 yards is merely, "Point it and pull. Don't think, shoot." :D

Art

[Mal H]

I wouldn't zero at 25 yds for a high speed round when you might need to hit something at a much longer range for physics reasons. Gravity is an accelerating force and it always starts at zero for a bullet when it leaves the barrel. So at 25 yds, the trajectory is very flat no matter what the velocity of the bullet happens to be. So you would think you have a magic rifle since round A with a muzzle velocity of 2500 fps has practically the same zero (that is, you don't have to re-zero) at 25 yds as round B with a muzzle velocity of 3200 fps. Yet at 200 yds, they are about 5 inches apart. But, if you zero at 100 yds, and don't rezero, those same rounds are only about 2 1/2 inches apart at 200 yds. As Art implied you have a much longer point-blank range by simply moving your zero point further out.

Granted, you don't normally use rounds with as wide a range of velocity as I used in the example, but it illustrates why a short range zero is undesirable for a high speed bullet.

[fisherman66]

'Course you are right Mal, but were talkin' about the 30'06 (although anything between the 260 and the 30'06 should come out about the same). The 25 yard zero works fine with standard high velocity "hunting" type cartridges for those who shoot well inside the MPBR. It ain't gonna cut it for the handloaders and/or the target flyboys. I use the 25 yard test to check for scope movement before each rifle season begins if I am unable to make it to the range beforehand. I'd agree with anyone who wants a 100 yard test to confirm a 200 (or whatever) zero. Just math.

[DWARREN123]

Go with what you are comfortable with. If you zero at 100 yards, with most rifle calibers, you will be good from the muzzle to about 200 yards.

[FirstFreedom]

As mentioned, it's not a good idea to trust it. As a very general rule of thumb, high-velocity bottlenecked cartridges (.308, .30-06, .270, etc), if zeroed at 50 yards for the "1st zero" will be once again very close to zero at 150 yards, at the "2nd zero". Then if limit your shots to 150 or 160 yards, you are good to go in a pinch by sighting in at 50 yards.

The better approach, in my view, is to:

1. Decide the kill zone size (diameter) for the intended game. Say, 12" for a deer.

2. Divide by 2 to get the kill zone radius (in our example, say, 6")

3. Then subtract roughly 2" from the radius (4" from the diameter) to account for field conditions and rifle performance (rainy, windy weather, bad trigger squeeze, un-rested wobbling hold, etc.). That gets us to 4" radius. If you don't have a lot of confidence in your rifle's accuracy, or your skill, then subtract more from your radius (say, 3"), or if you have a lot of confidence in your ability and your rifle, and will not shoot at game without using a field rest, then subtract less (say, 1" or 1.5") from the radius.

4. Consulting ballistic software, plugging in for your chosen load, the muzzle velocity, bullet BC, height of sight line over bore, ambient temperature, and barometric pressure for likely hunting conditions, find that specific range at which the bullet, on its way to the maximum, goes no higher than your adjusted radius (4") over the line of sight, and at the maximum, is exactly 4" below the line of sight, in this example. This is your MPBR - Maximum point blank range.

5. Consulting the software, given the MPBR with a -4" trajectory from line of sight, back up and voila, it will tell you the distance at which your second zero should be, and it will tell you how far over or under you should be at 200 yards to achieve that second zero. Sight in for that point at 200 yards. Or, if you do not have access to a 200 yard range, sight in for what the software says it should be for 100 yards (it will be higher than the line of sight.).

Now you're ready to always aim directly at the center of the vital zone no matter what distance the game is, provided that you first of course verify that the game is not beyond your MPBR range.

Oh yeah - you *always* have to also account for wind - that's a whole nuther set of skills. If it's windy, then you will probably want to limit your range to a lot less than your MPBR per above, unless you've practiced long shots in the wind a lot.

[tkcomer]

I use the 25 yard range to get my scopes dialed in, but I always move to whatever yardage I'm actually aiming for. I just use the 25 yard range to start off with.

[fisherman66]

4. Consulting ballistic software, plugging in for your chosen load, the muzzle velocity, bullet BC, height of sight line over bore, ambient temperature, and barometric pressure for likely hunting conditions, find that specific range at which the bullet, on its way to the maximum, goes no higher than your adjusted radius (4") over the line of sight, and at the maximum, is exactly 4" below the line of sight, in this example. This is your MPBR - Maximum point blank range.

What's the margin of error for the software? I'd guess it would be hard to figure out exactly due to bullet seating depth, bore shape and other variables. It seems that your exacting method (which strikes me as a handloaders methodology) should include a cronyvelocofeeter. Thank goodness we don't have that ugly metric system yet. Let the base 10 folk stew on that.

[Mal H]

There is no need for error correction in the software due to bullet seating depth, bore shape, jump to leade, powder type/weight, etc., etc. Once the bullet leaves the muzzle, none of those things matter in the slightest. The muzzle velocity, BC and all other external factors are the only things that count. All of those "internal" things are involved in the muzzle velocity, but as far as the SW is concerned, the only valid factor is the MV itself.

[fisherman66]

I understand Mal. I'm trying to figger out how the software calculates the MV. Without a crony, just using the software, what is the margin of error?

[Zak Smith]

It doesn't. You chrono your load. Modern ballistic software is pretty much "right on" for trajectory -- provided you've plugged in valid data.

The most important factors for zero distance and point-blank range are (in order): sight over bore distance, velocity, and BC.

-z

[Mal H]

Like Zak said, a chronograph is a given when using ballistic software. You can use velocity tables from reloading manuals and the like if you wish, but those figures are for "their" firearms/bullets/barrel/weather, not yours.

[fisherman66]

Thanks for the explanation Zak and Mal.

Now for those without a chronograph, having a 25 yard zero and a 100 rise of 2" (hypothetically speaking), it should be possible to calculate the MV with the BC and bullet weight right?

I ask because I don't have a chrony, and the 20" barrel on my 7x57 doesn't mate up with the couple of ammo boxes I have looked at (22" or 24"; can't remember for sure).

I keep putting off getting into reloading. Each time I get the funds together I start eyein' 'nuther "piece". Next one might be a K22 ohhhh or a Classic Steven's Favorite ohhhh or a Colt Cobra 38. I guess I need better impulse control.:)

[Zak Smith]

Short-range drop is a very bad way of calculating muzzle velocity. You're better off to borrow one or buy a cheap chrono (under $100).

-z

[Mal H]

Zak's right - buying/borrowing a chrono is always the best route to determining accurate muzzle velocities. However, as with any formula, it is possible to find one any one variable if you know the others. The problem is most ballistic software won't help you. In general they do not have provision for plugging in the drop (or rise), BC, etc. and calculating the MV. And I'm not going to try to figure out the formula. ;)

Another problem is that there is more than one velocity that will give a drop or rise at a certain distance. If you fire a relatively slow speed bullet, it might have a rainbow trajectory, so the measured 2" rise at 100 yds might actually be a drop of 10". A much higher velocity bullet might have the same rise of 2" at 100 yds yet the trajectory is much flatter than the first example; the bullet is still on the rise. Both examples assume a scope height is a factor in the calculations.

The best method of determining MV by measuring the drop is to fire the bullet perfectly flat and then measure the drop at 100 or 200 yds. There will always be drop using that method.

-Or- you can make your own ballistic pendulum for only a few bucks. Google for that term and you should find a few descriptions of how to construct one. (Though they aren't nearly as accurate as a modern chrono, they will give you an infield-of-the-ballpark value of the bullet's velocity.)

[Zak Smith]

For a typical .30 caliber hunting bullet, there's only 0.5 - 0.75" difference in drop at 200 yards per 100 fps difference in muzzle velocity. Not all that useful.

-z

[Mal H]

... especially when you consider that you have to have practically perfect aiming in order to have any semblance of accuracy in determining the MV.

[gedenke]

:eek: Wow, you guys have way too much time on your hands! :p While you guys spent the weekend discussing all the physics and thermo-nuclear-interplanetary-rocket-science-smart-guy stuff, I sighted the gun in at "about" 100yds and proceeded to head out in the woods in search of elk. Even though I didn't get a chance to take a shot, I feel confident that I would be able to hit the vitals from "close-enough-to smell" :barf: to around 200yds.

Oh, I say "about" because I took it down to the rock quarry near our hunt camp, and paced off appoximately 100yds. After getting it zeroed, I could center-punch any target in the quarry anywhere from 30 to about 120yds or so. Hence my confidence.

Thanks for all the in depth but "confusing" advice though!

[jmorris]

I like the Shepard scopes for large game at extended ranges. If you’re zeroing for 25 yds you don’t need a scope or a rifle for that matter. If the Shepard’s are too expensive for your tastes then I would suggest the “maximum point blank range” system for your zero. It’s the simplest method and requires the least amount of experience (distance judging, making corrections etc.).

[Zak Smith]

Maximum point-blank range for full-power rifle cartridges almost never involves a 100-yard zero.


_Bullet_ _BC_ _MV_ 0 50 100 150 200 250 300 | YARDS
308 (25) 0.340 2700 > -1.50 1.19 2.56 2.48 0.80 -2.65 -8.08 | drop (inches)
near zero 25.00 far zero 214.32
elevation maxima 2.71" at 122.65

308 (50) 0.340 2700 > -1.50 0.00 0.19 -1.08 -3.95 -8.59 -15.20 | drop (inches)
near zero 50.00 far zero 113.02
elevation maxima 0.28" at 81.88

308 (75) 0.340 2700 > -1.50 -0.18 -0.17 -1.61 -4.65 -9.47 -16.26 | drop (inches)
near zero 75.00 far zero 75.00
elevation maxima 0.00" at 75.52

308 (100) 0.340 2700 > -1.50 -0.09 -0.00 -1.36 -4.32 -9.05 -15.76 | drop (inches)
near zero 56.94 far zero 100.00
elevation maxima 0.13" at 78.55

[fisherman66]

If you’re zeroing for 25 yds you don’t need a scope or a rifle for that matter.

You are missing the idea that the bullet passes the axis of the scope at two points. If the first one is at 25 yards, the second one might be near 200 yards, depending on the trajectory. It works in reverse too (and even better since the margin for "measuring error" at two hundred is less than the margin for "measuring error" at 25). A zero of 200 yards might give you an alternative zero of 25 yards.

Brake on threw two the other side.

[MADISON]

I have been rifle and pistol shooting since 1960.
The only need I have for a 25 yard zero are my SQUIB LOADS.
1 in 12 twist with a 55 grain bullet.
I live in the City and have squirls, ground hogs and deer eating up my garden. I turned Ed Harris's 4 to 5 grains of Bullseye in a .223 Remmington sideways and use 5.6 grains of UNIQUE for my city load. It moves at about 1850 fps and at that range iss covered by a dime.

[sundog]

25 yards is 900 inches. I don't know what the firing tables are now (retired in 94), but the Army used the thousand inch (25 meters) range to set battle sight zero for the M16. Quick and easy.

Of course, once that's done, final adjustment can be done on a kd range to insure best accuracy. The concept mentioned by someone earlier is very simple, the bullet crosses the los twice - you just have to know where those two points are.

But, here's the other thing. Just because a particular load prints good at 25 yds, that's no insurance the it will at the other los crossing point. It just may not be a good load at ranges farther than 25 yards.

[castnblast]

I can't add anything to what's been said. 25 yds is o.k. to get you on paper, but 1/4" at 100 is not the same as 1/4" at 25. You really need to stretch your distance out to really pinpoint where your bullet is going. Also, there is no way you can tell which ammo is grouping tightest w/ out taking it down range. Use 25 to get your scope on, but you better do some down range shooting to pin point it.

[Eghad]

In the Army we zeroed our M16A2s at 25 meters. According to the FM the 5.56 crosses the axis at 25 meters and 300 meters. The last time I qualified on a range we checked our zero at 25 meters then went to the 300 meter pop up range and qualifed. I got 36 out of 40 hits on the range. I didnt miss any of the 300 meter targets with the issue sights. This was using issue M855 ball ammo. This was using iron sights no Aimpoint or EoTech.

according to the FM the bullet intersects the line of sight at 25 meters and 300 meters

You would pretty much have to know the internal and external ballistics of a round to know if you could do that with a certain round.

[Robert M Boren Sr]

I have for years sighted my scope in at 30 yds. It saves ammo in sighting in and it also gives a 300 yrd zero. It's been explained so good already. You still need to practice at different ranges. We pick rockslides and a good range finder and take a couple of shots. It not only confirms your zero, but builds confidence also. I have since went with a trajectory compensating scope, a Leoupold Boon n Crocket reticle. Stadia lines go to 500 yds and then you hold up from there. Already have taken shots to 750 yds and have yet to miss. Takes practice though.

[RangerHAAF]

I zero my red dot scopes and iron sights at 25 yards. My multi-powered scopes are zeroed at their maximum power at 100 yards. This has worked for me since I got out of the army.

[gedenke]

I too, was military trained on the M16(A2) in the Marines. If I remember right, we did our zero @ 25m and then moved out to 200, then 300, then 500. Granted, these were man-sized targets and all we had to do is touch black to score. Also, we usually had two or three days of practice that allowed us to "dial in" before qual day. But, of course, target/hunting style shooting is way different than military qualification, where close is good enough.