questions about rimfires & parallax.

Mr. Friendly

Mr. Friendly

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my brother and I were at a Wholesale Sports today, talking with one of the fellows behind the counter (middle aged, been hunting a long time, has experience). I told him about how I was thinking about the Winchester Wildcat Target/Varmint as my first rifle to plink with. mentioned how I was thinking about putting a Meuller APV 4.5-14x40 on it and he commented about how low quality a lot of the Chinese optics are.

I can't argue that point (about some Chinese optics), but then he said he'd recommend something like the 4x40 or 6x50 fixed power Weaver scope that I'm guessing is Japanese optics, but the entire design was all metal. not a plastic bit on it at all.

it was at that point that I mentioned about compensating for parallax. he laughed at that and said what parallax? at 50...100 yards? no way, 400 yards maybe, but for big guns.

so, now I have two conflicting thoughts as I've read, been told that you'd want to compensate for parallax and now I'm told you don't.

what's the full story that leads them to the two completely different conclusions? :confused:
 
Here is some information from Biathalon at Rimfire Central on calculating maximum parallax error:

Here are a couple of parallax equations that I have been meaning to post.

They are based on an article I read which confirmed the equations I derived. I won't include the diagrams at this time. If there is interest, I will figure out some type of program to draw with.

This almost belongs with a scope forum but there was a good explanation on this thread and I'd thought I'd add to it. I know that I was really interested to know this info as I am interested in using my rifle scopes at short distance and rimfire scope (I'm looking at the 2-7x28 Leupold) at long distance.

In either case, as mentioned by ShootNut, if your cross hairs are centered in the exit pupil (looking straight through the scope), there will not be any parallax error.

I'll provide two equations to simplify the illustration of the two following situations.

1) Short Range Parallax Focus and Shooting Long Range.
2) Long Range Parallax Focus and Shooting Short Range.

Variable (same for both situations):

X (PFD) = Parallax Focus Distance from Objective
Y (TD) = Distance to Target from Objective
Note:Units doesn't matter as long as you use the same units.

D = Objective Diameter
Note: Units doesn't matter. Error will be in the same units as the
units used for the Objective Diameter (mm).
(1inch = 25.4 mm)

Equation 1 (28mm objective, 60 yard pfd):

maximum error = (0.5)x(D)x(Y-X)
____________
(X)

example: shooting a target at 150 yards and your not even close to looking straight through the scope.

error = (0.5)x(28)x(150-60)
________________
(60)

= 21mm or 0.83 inches

Equation 2 (40mm objective, 150 yard pfd):

maximum error = (0.5)x(D)x(X-Y)
____________
(X)

example: shooting a target at 50 yards and your not even close to looking straight through the scope.

error = (0.5)x(40)x(150-50)
________________
(150)

= 13mm or 0.52 inches



If we use the 6x50 scope he recommended, and if it was a centrefire scope designed with a fixed parallax setting of 150 yards, when we plug those numbers into the formula, we find a maximum parallax error of 0.82 inches if you use it to shoot at a gopher at 25 yards. If you use it to shoot at a target at 50 yards its around 0.68 maximum error. So lets say the actual error is half that. Could you live with an error of 0.41 inches at 25 yards? If you are shooting off the bench and trying to hit a ping pong ball sized target at 50 yards, maybe its inconsequential. But if you are trying to hit a dime sized target at 50 yards, and that is certainly within the capability of the rifle, the error might mean something to you.
 
hey Grizz, so then I'm going to take it that I should understand this other fellows thought as being with his experience, he doesn't see the need to adjust for parallax.

I can accept that as a reasonable conclusion...especially so being when I was out shooting a few weeks back, we hit nothing. the targets at 100 yards had a couple holes in them, but were so far off from where they should be, it was inconsequential. granted, it seems only the Marlin 30/30 was sighted in properly whereas the Cooey .22LR and the Mauser .308 were not. :rolleyes:
 
If you are shooting offhand or from an unstable position, or shooting at fairly large targets like deer, I'd say parallax error is of no consequence. But when you put a rifle on a bench and try your best to see if you can shoot a clover leaf or ragged single hole, you will curse the scope that isn't set up for the correct parallax free distance. So I can respect the guys answer that in his opinion it isn't important. It all depends on the scenario. I would not want AO on a hunting rifle either. It would be a pain to have to make that adjustment on the fly. Also, it seems AO scopes have a narrower depth of focus than non-adjustable scopes.
 
At your shooting range, put your scoped rifle on a rest (shooting bags) with
the scope pointing the center of the target. Now without moving the rifle
move your eye from left to right and right to left, going from each edge of
the field of view while watching the cross hair "walking" on the target.

Now you have an idea of the parallax error for this scope at this
distance with this parallax adjustment. You can do the same moving
your eye up and down the field of view to see if the parallax error is the
same vertically.

You can use this method to see if the 100 yds adjustment on your scope is
really adjusted for 100yds (you have to be 100 yds from your target), you
can do the same for any distances.

Having some sort of ruler on the target help estimate error mesurement.
Draw a stripe with one inch black-white-black-white-black-white squares
on your target.

You can use a similar method to verify Mildot spacing at various ranges
and various power settings...

Jocelyn.
 
okay, so the parallax basically involves the drop or lift of the bullet and where it hits because of that at different distances.

if that's a concern for a rimfire at 50 yards to 100 yards, to ensure you hit the bullseye, why wouldn't it by such a concern in the field and you're trying to take down a deer? if you had a range finder and your deer is at 150 yards, but you set your scope for 50 yard shots what do you do? compensate your shot out of reflex because you know what the drop/lift would essentially be or have AO optics to adjust so you can calmly make the shot?
 
Parallax is an aiming error caused by the scope appearing to point at the target precisely, but it isn't because your eye isn't centered behind the ocular. A scope can be set to eliminate this error, only at one distance. The error is progressively greater at further or closer than that setting and the more your eye is off center. Its like the sights line up, but they aren't really.
 
Grizzlypeg said:
Parallax is an aiming error caused by the scope appearing to point at the target precisely, but it isn't because your eye isn't centered behind the ocular. A scope can be set to eliminate this error, only at one distance. The error is progressively greater at further or closer than that setting and the more your eye is off center. Its like the sights line up, but they aren't really.
Click to expand...
so what you're saying there is that you should learn how to place your eye properly behind the scope where having to adjust for parallax doesn't become so much an issue?
 
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That helps for sure. Having a stock that fits you and the scope well makes consistent alignment more natural and likely to be repeatable. When you have it right, you should be able to shoulder the rifle with your eyes closed, open your eyes, and your eye should be centered on the scope. You'll notice that the high end target rifles have adjustable cheek pieces and butt stock adjustment for position and length of pull. I'd say that must mean they consider it a critical element to consistency.
 
"so what you're saying there is that you should learn how to place your
eye properly behind the scope where having to adjust for parallax doesn't
become so much an issue?"

Yes, proper eye centering behind the scope is the best method for shooting
a non parallax adjustable scope at different distances.

The little parallax error won't make you miss a big game animal, at least if you
don't conciously look trough your scope at the edge of the eyepeice.

Jocelyn.
 
Grizz, you should get the CGN Indispensable Award! you're awesome and I've been peppering you with questions both on the forums and in private and you've met everything. you have my thanks! :D
 
Thanks Friendly. I ask lots of questions on here too and get great answers from people who are eager to share their experience. Nothing quite like these web forums.
 
If you want to use a (non-parallax-adjustable) hunting scope for target shooting at rimfire distances you will get better results if you use a lens cap on the ocular lens with a small hole drilled in the center. Sighting through the hole keeps your eye centered and minimizes parallax error. Flip ups are good for this because they don't move around.
 
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