Scope sight "rule of thumb"

[cdoc42]

Generally speaking, avoiding the more appropriate terminology of MOA, a 1-inch group at 100 yards translates to a 2-inch group at 200 yards, 3 inches at 300 yards and so on.

But what's the rule of thumb for scope settings? For example, one of my scopes indicates one click equals 1/4 inch at 100 yards. So today, my test shot was 4 inches low at 200 yards. I figured 4 clicks up would equal 2 inches at 200 yards. The next shot was 4 inches high, a total change of 8 inches!

What's the rule of thumb?

 

[bedlamite]

What's the rule of thumb?

There ain't one. Some scopes track properly, some don't. I've had to do the box test, then measure the distance between groups and figure out how much each click was.

 

[Scorch]

Scope manufacturers provide a manual with scope specs in it that tell you what the adjustments are per click. Most hunting scopes move 1/4" at 100 yds per click (I say most because there are some that are 1/8" per click, and some that are 1/2" per click). But just due to the extent of movement (8" at 200 yds by adjusting the scope 4 clicks), I would say you are seeing an aberration of some sort, either ammo or shooter or scope.

Most shooters shoot a group, adjust the scope, then shoot another group, adjust, and so on. From your post, it sounds like you fired one shot, then adjusted.

 

[jmr40]

If your scope is designed to move 1/4 MOA per click then 8 clicks should be 2" Most quality scopes will be pretty close, but it isn't uncommon for even decent mid priced scopes to be off a little. If you need to move POI 1" @ 200 yards it should be 8 clicks with most scopes. Sometimes you need 6 or 7. At other times you may need 9 or 10. The better the scope quality, the more accurate it will be.

The cheaper budget scopes are notorious for being inconsistent. Sometimes 1 click= 1/4" @ 100 yards, sometimes 1 click does nothing at all and at other times 1 click=1'. You can chase groups all over the target before finding zero with cheap scopes. And then hope it stays there.

 

[Mobuck]

" If you need to move POI 1" @ 200 yards it should be 8 clicks with most scopes. "

Better re-calibrate. With a 1/4" adjustment @ 100 yards, 8 clicks would move the POI 4" @ 200 yards.
Some scopes are more precise than others. You can use the clicks on some with fair confidence but I don't count on doing so.

 

[LeverGunFan]

A 1/4 inch click at 100 yards should equal 1/2 inch at 200 yards. The way most scopes work is that the turret screw bears against one side of the scope's internal adjustment tube, and there are springs that bear against the other side. Sometimes the springs aren't strong enough to move the internal adjustment tube completely when you turn out the turret screw, and then when you shoot the gun recoil causes the tube to move, giving erratic adjustments. One tip I've heard is to turn out the adjustment screw more than you need, then turn it back in to the correct setting. So for example if you need to adjust the screw 8 clicks out, you turn it out 12 clicks and then turn it in 4 clicks for a net of 8 clicks. That helps the spring move the internal tube to the proper setting.

 

[cdoc42]

Scorch, I was adjusting the scope for a 200 yard zero with 2 different bullets in 6.5mm Creedmore. I knew I was previously right on target with a 140gr Berger and one shot proved it. I noted the scope settings. Then I fired one shot with 140gr Sierra and it landed 4 inches low and 2.5 inches to the left. I surmised 4 clicks of 1/4" at 100 yards would raise the impact point 2 inches at 200 yards and 2 clicks to the right would be 2 inches. The next shot went 8 inches high and never moved to the right. But the observations posted here definitely agree with my experience.

The original Berger 140 setting was elevation 18.0 and windage 11.4. By the time I finally got the Sierra bullet into the desired impact point, E was 18.4 and W was 13.2.
I then moved the dials back to the Berger setting to see how reproducible the scope was
and much to my surprise the impact point was not the same previous location. I recaptured that point at E 18.2 and W 12.0. (There was no wind of any significance).

So I can't, with confidence, just switch loads and change the scope setting.

I've seen the same things discussed by others as well, using Burris, Nikkon and Leupold scopes - not super expensive, but not Tasco, either. A friend had the experience whereby he would make a change, fire a shot, and nothing happened. The next shot he fired showed a change. So it took recoil to move the setting he made -as discussed above. Frustrating when you're trying o be precise.

 

[zukiphile]

I've seen the same things discussed by others as well, using Burris, Nikkon and Leupold scopes - not super expensive, but not Tasco, either. A friend had the experience whereby he would make a change, fire a shot, and nothing happened. The next shot he fired showed a change. So it took recoil to move the setting he made -as discussed above. Frustrating when you're trying o be precise.

That's the thing about reputation; it may have a basis, but it is not guaranty. I've seen Leupolds that were junk. Tasco suffered somewhat from it's hisorical association with Kmart, But I've some Tascos that have proven durable, reliable and have repeatable settings.

When you are seeking repeatability in a scope, it can help to be repeatable in your adjustments. If you've ever adjusted a scope with turrets that feel sticky or muddy, you've probably guessed that there is more at work than just a ball, detent and spring exerting force on the internals.

If you turn a click beyond your desired setting then back, you might reduce or even eliminate the step of a shot or two to get the scope settled into its new adjusted setting. This doesn't address error in scale (one click not moving the reticle 1/8 or 1/4 inch at 100 yards), but it might deliver repeatability.

 

[Doyle]

Sometimes the springs aren't strong enough to move the internal adjustment tube completely when you turn out the turret screw, and then when you shoot the gun recoil causes the tube to move, giving erratic adjustments.

I know it might seem odd, but long ago I got into the habit of tapping the turrets several times after doing any adjustment just to "settle the springs".

 

[Art Eatman]

I read about the "settle the springs" thing way back when. I figured that it couldn't hurt, so I tap gently with the handle of a small screwdriver. Never had "scope wandering" problems.

If a click is 1/4" at one hundred yards, it will be 1/2" at 200 yards.

 

[ndking1126]

Agree with most here. I have a Bushnell scope that is probably 40 years old that says is 1/4" at 100 yards. It jumps from rifle to rifle periodically and each time I re-sight it in, I forget that it actually moves 1/2" at 100 yards per click. A few wasted rounds and a little time isn't the end of the world, but you'd think I'd write the correct adjustments down so I'd remember. Haha

Probably off topic from the OP, but I've had to tap the turrets before. I have a cheaper Simmons rimfire scope that after a couple of years would not adjust for windage. I was about to throw it away but read that sometimes, for whatever reason, the mechanicals inside get stuck. I took it back to the range, adjusted it one more time, tapped the turrets and much to my surprise it worked. Haven't had to adjust it since and it's kept its zero without issue.

 

[Ifishsum]

My rule of thumb is to adjust a little less than the numbers say. I have a number of decent but lower end scopes and it seems pretty common that they move closer to 1/2 than 1/4 MOA even when so marked. As long as they hold zero and track okay it doesn't bother me.

 

[T. O'Heir]

Scope clicks have nothing to do with MOA or group size. They're a specific movement for the group at 100 yards set by the manufacturer. 1/4" per click means the group will move 1/4" at 100. So if you're in the bull at 100 and want to be 2" high at 100, you move a 1/4" per click scope 8 clicks up.
Like Scorch says, read the Manual.
"..."settle the springs"..." There's no such thing.
Just remember that the cartridge and bullet weight matters. For example, a 165 grain Hornady factory load .308 sighted in 2" high at 100 will be on target at 200 and 8.6" low at 300. According to their new site's ballistics charts.

 

[Doc7]

Scope sight "rule of thumb"

I am dealing with sighting in a muzzleloader right now going into shot 12 next time I can go to the range.

When I don't adjust the scope, it cloverleafs at 50 and is MOA at 100, which is awesome for a muzzleloader shooting pellets.

However, when I adjust the scope, a Used Vortex Viper 3-9x (suspect this is why he sold it!) sometimes it adjusts 1/8" per click and sometimes 1/2" per click, at 100 yards! Occasionally I shoot a few shots in a row just to make sure it's not me or the gun or the load! It's the clicks and inconsistency.

Once the muzzleloader season ends in November I will be sending it back to Vortex for a once over. It is very frustrating to try and sight it in right now. I will try the tapping etc but I think that would show up in group sizes if that was my problem, and it's not.