How to tell what default "zero distance" is for a revolver

[K.Mooneyham]

This forum is a vast wealth of firearms knowledge, so I know this one should get a pretty good response. I own a Taurus Model 66 .357 Magnum 7-shot revolver. It has adjustable sights that click for elevation and windage. However, with the sight centered and flush, how do I know what the default "zero distance" is for this pistol? The manual tells how to adjust the sights but not what distance it was designed to shoot at WITHOUT changing the elevation of the sight. Is there any way to figure this out without taking careful single-action rested shots at various distances and seeing what hits closest? That would be hard to do at the range it would seem, as well as kind of time consuming. Thanks in advance.

[K.Mooneyham]

Maybe I'm doing a poor job of wording what I'm asking. If a pistol (or revolver) had fixed sights, the manufacturer would design it to have point of aim equals point of impact at a specific distance if you use ammunition like what they used, say standard pressure 158 grain lead round nose for .357 Magnum. To hit higher or lower, you'd have to aim higher or lower. If you used lighter or heavier bullets, you would also have to adjust where you aim to compensate for that. However, the adjustable sight gives you the ability to compensate and keep your sight picture the way it aught to be. But I'd still think that there would be a specific distance that they'd design it to shoot at if the sight is left in the default (fully down) position. I'm trying to figure out if there is a way to know what that distance is since Taurus didn't bother to put it in the manual.

[mr surveyor]

It's always been my understanding that most factory revolver sights (specifically "fixed" sights) are tuned to 20 yards

[JALLEN]

My GP100 manual has no such information either, and has adjustable sights.

Maybe they realize that people will read the Zero point, try to hit it and think the gun is defective if they don't hit it exactly. Or maybe very few owners record where the sight was set, then adjust it and can't remember where the factory zero settings were.

Maybe it is something you have to figure out for yourself, or for each pistol.

[Excaliber]

This forum is a vast wealth of firearms knowledge, so I know this one should get a pretty good response. I own a Taurus Model 66 .357 Magnum 7-shot revolver. It has adjustable sights that click for elevation and windage. However, with the sight centered and flush, how do I know what the default "zero distance" is for this pistol? The manual tells how to adjust the sights but not what distance it was designed to shoot at WITHOUT changing the elevation of the sight. Is there any way to figure this out without taking careful single-action rested shots at various distances and seeing what hits closest? That would be hard to do at the range it would seem, as well as kind of time consuming. Thanks in advance.

You could come up with a rough estimate by shooting a couple of small groups carefully from a rest at two different distances, say 5 and 25 yards, and matching the results with a trajectory table for the load you're using. It would still be a guess, but it would be a closer guess.

To me that seems like a lot of trouble. It would be much simpler to fire a few shots at several different distances and see where the gun / load / sights / shooter combination comes closest to point of aim.

[K.Mooneyham]

I'm sure I'm just being overly picky about stuff. Fixing things for a living using a manual, you get used to working from a starting point, or having specs to go by. I guess I'm just more of a science than an art kind of guy.

[MoJo]

Almost all adjustable sights zero a bit above bottom. Fixed sight guns are zeroed by changing the height of the front and or rear sight. With a new handgun gun with adjustable sights I turn the sight all the way down then add 8-10 clicks then shoot it and make necessary corrections.

Your zero may be different than mine due to differences in vision, how we hold the gun, and physical differences.

[lfinsr]

This forum is a vast wealth of firearms knowledge, so I know this one should get a pretty good response. I own a Taurus Model 66 .357 Magnum 7-shot revolver. It has adjustable sights that click for elevation and windage. However, with the sight centered and flush, how do I know what the default "zero distance" is for this pistol? The manual tells how to adjust the sights but not what distance it was designed to shoot at WITHOUT changing the elevation of the sight. Is there any way to figure this out without taking careful single-action rested shots at various distances and seeing what hits closest? That would be hard to do at the range it would seem, as well as kind of time consuming. Thanks in advance.

If it has an elevation adjustment it would not have a "default" zero. I would suggest you use an online ballistics calculator and find the bullet trajectory for the load you're using. One of the pieces of data is the height above the barrel center of the sights, or more often a scope. It might give you some surprising data that could potentially change where you set the zero.

Larry

[K.Mooneyham]

This forum is a vast wealth of firearms knowledge, so I know this one should get a pretty good response. I own a Taurus Model 66 .357 Magnum 7-shot revolver. It has adjustable sights that click for elevation and windage. However, with the sight centered and flush, how do I know what the default "zero distance" is for this pistol? The manual tells how to adjust the sights but not what distance it was designed to shoot at WITHOUT changing the elevation of the sight. Is there any way to figure this out without taking careful single-action rested shots at various distances and seeing what hits closest? That would be hard to do at the range it would seem, as well as kind of time consuming. Thanks in advance.

If it has an elevation adjustment it would not have a "default" zero. I would suggest you use an online ballistics calculator and find the bullet trajectory for the load you're using. One of the pieces of data is the height above the barrel center of the sights, or more often a scope. It might give you some surprising data that could potentially change where you set the zero.

Larry

Alright, I went and found a pretty nice ballistic calculator. Somehow I had always thought that a pistol should be sighted in close. However, it looks like my best bet might be to sight it in for 25 yards, and it will be fairly flat out to that distance, then drop off after about 30 or so yards. So, I'm going to begin at 7, move to 15 and then to 25 for the final sight-in. Thanks for the advice.

BTW, the calculator I used is found at http://gundata.org/ballistic-calculator/ for anyone who might want one. It lists a LOT of calibers and several commercial loads under each caliber.

[lfinsr]

Alright, I went and found a pretty nice ballistic calculator. Somehow I had always thought that a pistol should be sighted in close. However, it looks like my best bet might be to sight it in for 25 yards, and it will be fairly flat out to that distance, then drop off after about 30 or so yards. So, I'm going to begin at 7, move to 15 and then to 25 for the final sight-in. Thanks for the advice.

BTW, the calculator I used is found at http://gundata.org/ballistic-calculator/ for anyone who might want one. It lists a LOT of calibers and several commercial loads under each caliber.

Because the trajectory of a bullet is always an arc, there will be 2 points at which it is "zeroed." I don't know what you're shooting but I picked a standard load of 158gr. HP. If the gun is zeroed at 10 yds then from 0-50 yards you'll be accurate to about 1" diameter anywhere in that range. If you're sighting it in for self defense that would be a good starting point. If, however, you're shooting targets at single distance you would want to sight it for that distance.

For those of you that use an Android phone Strelok/Strelok+ is a great app (no affiliation, just a happy user.) The former is free and latter is ~$5. Well worth the money. I don't think there is a version for Apple but I'm sure there's an equivalent.

Disclaimer: I am far from an expert on the subject and I didn't stay at a Holiday Inn last night.

Larry

[K.Mooneyham]

Alrighty...went to the range with the Taurus today. Rear sight had to go up 12 clicks to get it zero'd at 7 yards to start, using .38 Special 130 FMJ. Had to add another 3 clicks up (total 15 up) for zero at 15 yards. And finally, when I moved to 25 yards, it was initially hitting so low with the rear sight at that 15 clicks that I was off the bottom of the paper. That was a FOOT below where I was aiming, center of target. I had to take the rear sight all the way up to 22 clicks before it was up high enough. However, when I use the ballistic calculator, it doesn't show it being off a foot when zero'd for 7 yards, but shooting at 25. The trajectory on the calculator shows it should be high at 25 yards when sighted in at 7 yards. So now I am confused.

I guess I need to get a book or take a class or something.

However, my Taurus is zero'd and there was little appreciable difference in point of impact at 25 yards between the .38 Special 130 grainers and the .357 Magnum SJSP 158 grainers that I fired after that. However, there is quite a difference in how much they smacked my hand and how much they would smack something solid at that distance.

(Edited to add: no pics because I'm not really that great a shot. I did alright for me, but I know I'm NOT in the same league with many of you.)

[lfinsr]

There are may other factors involved in ballistics calculations over and above what is provided on the site you posted a link to but they wouldn't have any affect under 300-400 yds. However, at close range it should be very, very close.

The most likely error was the sight height. On a pistol with iron sights it would probably be somewhere around .5" depending on the thickness of the barrel. The default for most of the calculators I've seen is 1.5", the normal height of a scope.

It will work. Just recheck the data you put in and change the default "distance to show" on the advanced page to 100 yds or less. The data is more meaningful when you narrow it down to the range you're working with. I suspect you're not shooting deer at 500 yds with your pistol.

Larry

[K.Mooneyham]

There are may other factors involved in ballistics calculations over and above what is provided on the site you posted a link to but they wouldn't have any affect under 300-400 yds. However, at close range it should be very, very close.

The most likely error was the sight height. On a pistol with iron sights it would probably be somewhere around .5" depending on the thickness of the barrel. The default for most of the calculators I've seen is 1.5", the normal height of a scope.

It will work. Just recheck the data you put in and change the default "distance to show" on the advanced page to 100 yds or less. The data is more meaningful when you narrow it down to the range you're working with. I suspect you're not shooting deer at 500 yds with your pistol.

Larry

I changed the both the sight height (I measured it as 7/8 of an inch from top of sight to centerline of the bore, roughly .9 inches. Also, I did change default distance to show to 100 yards. That is why I am scratching my head on this thing. There has to be something I'M missing, I just can't figure out what. I do appreciate the advice, though. If you can think of something else, feel free to put it up.

[DocV]

If you know how much you need to move your point of impact and your sight radius you can calculate how much you need to change either the front or rear sight to adjust you sights. Of course, all of the calculations have to be made using the same units and sight radius is often measured in inches. Suppose you have to move your point of impact 4 inches up at 25 yards.
1) Convert yards to inches.
We are using 25 yards so we have 25*3*12=900 inches
2) Divide the number of inches you need to move the point of impact by the distance in inches.
For our example, this is 4/900.
3) Multiply the result in part 2 by your sight radius.
As an example, if you have a sight radius of 6 inches, you would need to adjust the rear (or front sight) by
6*4/900 ( .0266) inches