Zeroing offset optics

BeaverMeat

BeaverMeat

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I am going against the grain with my custom SKS project and trying something not seen too often here in the west.

An offset scope mount.

I am not going to get into a discussion of why I chose this setup... I know an offset scope is not as accurate as centered mounting, but c'mon. It's an SKS. I have done some test mounting and I have found much benefit to this style of mount for an SKS.

Now, does anyone have an experience in this setup? What is the proper way to zero it in?

Should it be parallel with the bore so that the POI is always 1" to the right of center? Or should the scope windage be rotated as to have the sight line cross the bullet path. example:

Zero so the POI is 11/16" right of center at 100 yards, 5/16" right of center at 200 yards, dead on at 300 yards, 5/16" left of center at 400 yards... etc.

Any thoughts?

(don't bother to convince me not to do it... the mount is being programed for the CNC as I write this)
 
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I think it would be easier to keep it parallel with the barrel. Then just put the bullseye where you know the bullet is going to hit
 
Perhaps...

I am leaning more toward the sight line crossing the bullet path. With this method the error of the scope offset neutralizes itself with increased yardage. Making it a bit more practical as a hunting/rodent eradicator rifle.

Hmmm... going to rake a bit of pondering.
 
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The 7.62 Russian short is not a round noted for it's long range capability. The common wisdom is that the optimal BZO for the common weight and velocity of the 7.62× 39B is either 25m or 35m. These zeroes allow you to keep a fairly tight ballistic path out to 200 to 225m.

-S.
 
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Meat. I would sight it in like you explained so that its left at 100 and then right of target past the poi poa
This keeps the ranging in your head a lot simpler

Do it!!
 
Mr.4x4 said:
Meat. I would sight it in like you explained so that its left at 100 and then right of target past the poi poa
This keeps the ranging in your head a lot simpler

Do it!!
Click to expand...

That is the conclusion that I came to.

I will zero at 200m as opposed to 300 yards.

1" offset with a POI of 1/2" to the right at 100m, dead on at 200, 1/2" to the left at 300, and 1" left at 400.

Just needed some reassurance that Ichad the right idea in my head.
 
BeaverMeat said:
That is the conclusion that I came to.

I will zero at 200m as opposed to 300 yards.

1" offset with a POI of 1/2" to the right at 100m, dead on at 200, 1/2" to the left at 300, and 1" left at 400.



Just needed some reassurance that Ichad the right idea in my head.
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bad idea, a POI that shifts in both planes depending on range is a nightmare. Don't forget, its an SKS, it will never hit POA at any range under any circumstances let alone at distance. A parallel zero is the smarter option. Without any wind, your bullet will always(in theory, it is an SKS) be a fixed distance off(to the left) of POA regardless of range. We're talking what, 1.5"-2" windage offset? An impact on target at range that is 2" left of POA is amazing performance for an SKS and the likely surplus ammo you're running. With your converging zero and any kind of wind, you'll have no idea where to hold or if its the wind or the zero that's causing serious drift. Go with a parallel zero an forget that the POI is not the same as POA. This will keep you thinking about holdover and any hold-off as opposed to worrying about holdover, hold-off, and how that relates to your converging zero.

TDC
 
I have this same issue with my M1D. After a bit of experimenting, I concluded that I couldn't realistically fine tune the group placement relative to the amount of sight offset using Milspec ball. The dispersion of the ball ammo is one of the problems, and the fact that a Garand is at best 1.5-2.0 MOA accurate in Sniper trim is the other. The 1.5-2.0 MOA being more than the amount of mechanical scope offset, so there is going to be some overlap.
The idea of having the group centered at the maximum realistic useable distance of the rifle/cartridge has merit. In this case, without an extremely accurate Rifle with accurate ammo the amount of overlap due to the mean radius of the group at any particular distance past 100m would preclude fine adjustments.
If the maximum group size was no larger than the amount of scope offset, then fine tuning the zero would be easy. However, I have not personally seen any SKS rifles shoot 1" groups at 100m, so the best you could hope for would be to center the group at the max useable distance and live with the minor offset at the closer ranges.
 
Yes it is a sks so were talking minute of oprahs ass here. So really a bit left or right isn't that hard to guesstimate. It's not a precision rifle so there will be error but who cares as its his gun and a fun project
 
With any method you have bullet drop due to gravity. I would think that if you were to zero so the bullet is always the offset to the side the scope is one will keep it simple. In theory, a perfect world, the POI would always be the scope offset from the POA. The bullet would always drop the amount based on the range and trajectory. My .02 worth, if you mount offset, then zero with the offset in mind. If it's 2" to the left then POI is 2" left of POA. Kentucky windage 2" right.

The effective range of you will be the determining factor. If you shoot good at 100 then zero 100.

OR Zero POI and POA for windage at 300. POI is always to one side but the closer you get the farther apart the POI and POA get.
Then you have to worry about where to zero elevation. If the scope has elevation presets then zero accordingly. If not zero to the range you are likely to be using. Then adjust for the extra distnace as required.
 
Usually, I would not think to scope an SKS. But the SKS I have chosen is surprisingly accurate (PPU FMJ) in comparison to others I have shot. (no paper proof, I don't file) It's a '51 Rusky refurb with a mint non-chromed barrel. I have not shot past 100 yards with it yet, so I will see what develops once scoped.

For the record, I will be using a reproduction PU scope from the Ukraine (made by Photoprylad) I am also having custom turret rings made up that will be calibrated for the 7.62x39 once I sort out the ballistics.

Not going too far into detail... as most gun snobs would suggest. My project is stupid because I am spending too much time and money on a 'cheap' gun. :rolleyes:
 
You know there is such a thing as spin drift. In fact you might want to be about 1-3/4" left of bull at 100y to be on the bull at 200, so having the optic on the left side of the gun is actually helping correct for drift in a manner of speaking.
 
fuzzynuts54 said:
You know there is such a thing as spin drift. In fact you might want to be about 1-3/4" left of bull at 100y to be on the bull at 200, so having the optic on the left side of the gun is actually helping correct for drift in a manner of speaking.
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Spin drift at 200 is a non issue. Coupled with an sks and surplus ammo, its not worth mentioning.

Tdc
 
BeaverMeat said:
Usually, I would not think to scope an SKS. But the SKS I have chosen is surprisingly accurate (PPU FMJ) in comparison to others I have shot. (no paper proof, I don't file) It's a '51 Rusky refurb with a mint non-chromed barrel. I have not shot past 100 yards with it yet, so I will see what develops once scoped.

For the record, I will be using a reproduction PU scope from the Ukraine (made by Photoprylad) I am also having custom turret rings made up that will be calibrated for the 7.62x39 once I sort out the ballistics.

Not going too far into detail... as most gun snobs would suggest. My project is stupid because I am spending too much time and money on a 'cheap' gun. :rolleyes:
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Check out the guy in the US that made his Norc into a 1 MOA gun. should provide some useful reading and ideas for what to do.

link: http://thefiringline.com/forums/showthread.php?t=154057

And some scope inspiration: http://forums.gunboards.com/showthread.php?115490-Scope-mount-for-Yugo-sks
 
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TDC said:
Spin drift at 200 is a non issue. Coupled with an sks and surplus ammo, its not worth mentioning.

Tdc
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ahhh ####, your right. I had looked it up on my app, I had never looked up a medium velocity cartridge so I was a bit surprised but meh, that's what it says..... I just looked into it again, I had a wind value on as well. So ya, make that spin drift a couple c-hairs. Lol. Actually about .3" drift at 200y with a 100y zero.
 
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Had another thought on the offset scope. You may want to concider setting the sccope on a slight skew to the barrel.
Instead of the horizontal being well, horizontal, rotate it slightly. Still trying to think which direction, clock wise/counter clock wise.
Reason... If you are going to use range indexed turrets, as you adjust your range the "cros hair" is moved down to make you point the rifle higher. If you are zeroed at 100 and adjusted to say 200 the elevation would be correct but the shot will go to the left as you increase your distance. (assuming the scope is on the left side). If you cant the scope in the mount, as you change your elevation the windage will also move. This can be easily experienced with a poorly aligned scope centered over on any rifle.

Now on that same thought, if you are adjusting your elevation with indexed turrets you may as well go with index turrets for the windage.
Example Increase elevation 3 clicks and 1 click in windage. You would have to make sure you can easily and deliberatly return to 100 zero via index marks etc.

Almost sounds like the scope will be worth more than the rifle but then again isn't that the way it works anyways?
 
fuzzynuts54 said:
ahhh ####, your right. I had looked it up on my app, I had never looked up a medium velocity cartridge so I was a bit surprised but meh, that's what it says..... I just looked into it again, I had a wind value on as well. So ya, make that spin drift a couple c-hairs. Lol. Actually about .3" drift at 200y with a 100y zero.
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Not an issue.;)

Beermaker said:
Had another thought on the offset scope. You may want to concider setting the sccope on a slight skew to the barrel.
Instead of the horizontal being well, horizontal, rotate it slightly. Still trying to think which direction, clock wise/counter clock wise.
Reason... If you are going to use range indexed turrets, as you adjust your range the "cros hair" is moved down to make you point the rifle higher. If you are zeroed at 100 and adjusted to say 200 the elevation would be correct but the shot will go to the left as you increase your distance. (assuming the scope is on the left side). If you cant the scope in the mount, as you change your elevation the windage will also move. This can be easily experienced with a poorly aligned scope centered over on any rifle.

Now on that same thought, if you are adjusting your elevation with indexed turrets you may as well go with index turrets for the windage.
Example Increase elevation 3 clicks and 1 click in windage. You would have to make sure you can easily and deliberatly return to 100 zero via index marks etc.

Almost sounds like the scope will be worth more than the rifle but then again isn't that the way it works anyways?
Click to expand...

Uhh......No. Likely the dumbest idea I've heard in a long time. I see where you're going with it, but there is no way to control the compound movement each "click" will induce in each axis. The windage offset will not change with range provided the wind is zero. Two parallel lines remain parallel indefinitely. Zero the optic like any other with the exception of your POI being right of your POA by the amount the optic is offset from the bore. Keep it simple.

TDC
 
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