Turkeytider
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Is this possible? I`m looking at a .17 HMR rifle with a scope that`s set at 50 yards parallax and would like to zero at 100 yards. What, if any, issues should I expect shooting at 100 yards?
Zeroing a Scope With 50 yard Parallax At 100 Yards ?
- Thread starter Turkeytider
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An easy check is to securely mount the rifle in a vise or sandbags and then look through the scope at a 100 yard target. Move your eye all around and see how much the reticle appears to move. That's the maximum parallax error for that distance.
The good news is that unless your shooting technique Is pretty bad, your actual parallax error won't be nearly that much. The more closely your eye is centered in the scope, the less error there will be, so chances are it won't be much of a problem.
The good news is that unless your shooting technique Is pretty bad, your actual parallax error won't be nearly that much. The more closely your eye is centered in the scope, the less error there will be, so chances are it won't be much of a problem.
Hugger-4641
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50 to 100yd is not going to be enough error for you to notice unless you are capable of dime sized groups. If you are that consistent with your technique and cheek weld, then parallax error is not going to affect you anyway.
ivanthehunter
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If your careful you can adjust the front objective ring on some scopes which locks the objective glass. Then you can turn the front glass to reset parallax to whatever distance you want... then re-lock with outer ring.
i have done it to a few scopes.. just don't do it to a scope that's worth big money..
In case you breach the nitrogen purge.
regards from Ireland..
i have done it to a few scopes.. just don't do it to a scope that's worth big money..
In case you breach the nitrogen purge.
regards from Ireland..
Last edited:
Turkeytider
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Thanks all! I think I`ll just not worry about it. Hugger, I WISH I could shoot dime sized groups! This will be a fun range gun that`ll probably not be shot more than 150 yards, if ever that. I have a tendency to over think things anyway.
Special thanks to Ivan. The Emerald Isle is one beautiful place!
Special thanks to Ivan. The Emerald Isle is one beautiful place!
Varminterror
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The formula for calculating the maximum error potential from point of aim due to parallax is:
(Max error radius) = (objective diameter)/2 * abs ((target range) -(parallax setting range)) / (parallax setting range)
So a 40mm objective with a 50yrd fixed parallax, fired at 100yrds, will allow a maximum error from POA of 40/2*abs(50-100)/50 = 20*50/50 = 20mm.
So the fact you chose a 50yrd optic might allow about 3/4” error between poi and POA, potentially adding a maximum of a touch over an inch and a half edge to edge into 100yrd groups.
We had a pretty interesting thread recently on parallax error potential, might be worth looking up.
(Max error radius) = (objective diameter)/2 * abs ((target range) -(parallax setting range)) / (parallax setting range)
So a 40mm objective with a 50yrd fixed parallax, fired at 100yrds, will allow a maximum error from POA of 40/2*abs(50-100)/50 = 20*50/50 = 20mm.
So the fact you chose a 50yrd optic might allow about 3/4” error between poi and POA, potentially adding a maximum of a touch over an inch and a half edge to edge into 100yrd groups.
We had a pretty interesting thread recently on parallax error potential, might be worth looking up.
Varminterror
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How exactly would a shooter adjust to compensate for parallax?
Hint - it’s not a thing.
Turkeytider
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Which is a good thing, regardless. Sort of " enforced shooting discipline "!
Hugger-4641
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I'd like to know myself, maybe I missed something. So far the only thing I know to do if you don't have a correction knob, and even if you do, is to keep your head position/cheek weld consistent and make sure you have a full sight picture in the scope. Is there something else?
AJC1
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The red neck fix. Move your face back until you have a black ring and a picture in the middle of the scope. The black ring needs to be equal on all sides and your eye is in the center, ready to fire.
Skylerbone
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In an ideal world that’s all it would take and we would never need to dial out parallax error. But...we live in the real world where consistency is the rarest of birds. An added few ounces of cheek to stock pressure, a 1/4” difference fore or aft placement, and any given group adding these factors as compared to the original zero group fired will ruin legitimate good groups.
The tale of a great rifleman who could overcome any deficiencies of his equipment never comes with a recognizable name.
Hugger-4641
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So if I understand you correctly, if all other variables were removed, you should still be able to shoot 1- 1/2" groups with that parallax error?
AJC1
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I would bet the extreme spread is a lot further, but if you have decent consistency that's probably reasonable.
Varminterror
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Yes, but no. Yes, that 1.57” is the max spread ONLY due to parallax… but that assumes you have a rifle which shoots 0.0” groups at 100yrds… I don’t own any of those…
The math I described above shows that the maximum contribution of parallax error is +/-3/4”, in congress with the magnitudes of the other errors.
So if you have a rifle capable of say, 1” at 100 yards when using a parallax free optic arrangement, your 1” rifle might swing clear out to 1.8” just due to parallax error. Doesn’t seem THAT bad, but if I consider most of my rifles shoot 3/4moa or less, and that parallax error swings them out to 1.7moa… or my 1/2” rifles swing out to 1.6”… well, that just sucks…
In reality, most of us won’t ever error at the maximum, but even if I experience 1/2 of the maximum potential error, it adds about 50% to my group sizes… again… that sucks…
Reminding here - experiencing 50% of the max possible parallax error in a 3-9x40mm really only takes about +/-1mm side to side shifting. How confident are you in your ability to repeatably position your eye within 1mm of center for every. single. shot. in. every. single. position. ever…? With the consequence that tilting 1mm in or out means I fly shots an extra .35” outside of my normal 3/4” or smaller groups.
Hard pass from me.
Turkeytider
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As a relatively new rifle shooter I`ve found it very amusing that one doesn`t get very far at all in a discussion of accuracy, precision, etc. before said discussion becomes more than a little academic!
Varminterror
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It’s all physics. Physics of light coming into optics to reach our eye, physics of combustion and gaseous expansion as bullets are accelerated, and physics of projectiles once a bullet leaves a bore. A little thermodynamics here and there whether internal ballistics or atmospheric conditions…
We explore math and science to better understand the world God wrought around us. Ballistics just happens to be one of the more pleasurable pursuits in that exploration.
Turkeytider
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WOW!! Sure makes shotgun shooters look like simpletons!
You could try centering your eye the same for every shot, thus minimizing the effect. Another try would be to cut a disk the size of the objective lens, with a hole in the center that causes the light rays closest to the center of the lens to provide less parallax than the total lens. The image will have less brightness, but the reduced parallax will allow tighter groups.
Skylerbone
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I suppose because you may be looking at the explanation rather than the answer which was given: dial it out. If a person cares not about accuracy then there is no need to investigate the matter of parallax further, simply plug away as you were.
It is given that not all shooting requires sub-MOA accuracy but I agree that devoting both time and expense in the pursuit of shooting only to potentially double group size with a correctable condition...sucks.
Unlike a typical shot shell , precision rifles use telescopic sights, shoot 1 projectile, and the trigger is not slapped. Furthermore implying the skill set necessary for both is in any way related is the poke of a simpleton who remains unenlightened. Sharing good information based on science is not snobbery, it’s educational.
If you hate math there are parallax calculators online which will demonstrate the veracity of the above posts and you can customize input and divine the precise amount of potential error to add. Shooter + rifle + parallax, why not eliminate it?
Turkeytider
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I`m not sure mind you, but I think I`ve been insulted. If that`s true, then I`m not sure why. My statement about the academics involved with rifle shooting was in no way meant to offend. I was merely alluding to the fact ( and I know it`s a fact after 60 some odd years of shotgun shooting ) that rifle shooting is a more involved pursuit. In no way would I assert that " the skill set necessary for both is in any way related " , because it`s not. As the OP, this thread`s really drifted in a direction that I had no idea that it would.
Thread drift happens, differing opinions aren't automatically insults, math is often used to explain parallax error, some people scoff at parallax error, others worry much about it.
To the OP, there will be slight parallax error at any yardage other than 50 if your eye isn't centered, enough to matter? How small do you need to shoot? The posters have given you a great idea of the potential max error. Are other scopes perhaps an option?
To the OP, there will be slight parallax error at any yardage other than 50 if your eye isn't centered, enough to matter? How small do you need to shoot? The posters have given you a great idea of the potential max error. Are other scopes perhaps an option?
Skylerbone
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My apologies for the jab, meant as a return to the idea of shotgunners seeming less refined. I have an enormous respect for those who wield a firearm that requires so much instantaneous input from the shooter while offering him little advantage. It is a skill set I have attempted to acquire that eludes me still.
I will take care to traverse the High Road in more diligent fashion and again, my apologies @Turkeytider
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