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Support Equipment For PCP/HPA/CO2 and springers ,rams => Optics, Range estimation & related subjects => Topic started by: wahoowad on June 24, 2017, 11:25:16 AM
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Having a brain cramp...should be able to figure this out but can't.
I have a standard mil-dot scope where 1 click = 1/4" at 100 yards. My home range is 35 yards. What is the formula to determine the # of clicks of needed for a given amount of adjustment I need to make. This morning I'm working with about 3/8" off but want the formula for future reference.
Thanks
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100/35=2.85
100 yards divided by your 35 yard distance gives the number of clicks at 35 to equal 1 at 100. So in use, 3 clicks at 35 equals 1/4" at 35 yards.
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I don't know the answer but would like to guess.
35 yards is 35% of a 100 yards, and one click is .250 at 100 yards.
35% of .250 = .0875 so each click at 35 yards should move .0875 ?
3/8=.375 so .375 divided by .0875 = 4.285
So you would need to move 4 clicks ?
Like I said this is only a guess, can anyone who made good grades in math confirm ? :o
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This is why I will never buy another scope thats turrets aren't in the same measurement system as the reticle. Just an extra layer of confusion when you are trying to make a quick rezero
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4 clicks an inch at 100 yards would give 8 clicks at 50 yards and 16 at 25 yards. Midway between 50 and 25 yards is 37.5 yards and the ratio of clicks would make it 12 to move the reticle an inch.
I would always guesstimate like above in my head, and paper too! ;-)
I'm sure there is a formula with minute of angle that would give you the exact number but I don't know it.
Taso
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I'm physically and mentally lazy...
ChairGun range card...
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My range is also 35 yards. My non-scientific way of zeroing a new scope: Shoot and see where it hits. Full turn of each knob in whatever direction if needed to move it close to where it should be, then half a turn to get it closer. Then start the fine tune process by shooting a string of 3 pellets, then 4 - 8 clicks, a 3 shot string, and keep this going till I get it dialed it. Using this method, I can usually get in the bullseye within 12-15 rounds.
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IF you can attach your rifle firmly to your shooting rest or IF you have a helper-
Hold on a target and fire one shot. Then place the reticle back on the target and, IF the rifle is stable and will not move, move the turrets to place the reticle on the hole made by the shot. Several IF's here but it does work for one shot zeroing.
Otherwise, 4 (or 8 depending on scope specs) clicks equals 1 inch at 100 yards equals 1/2 inch at 50 yards equals 1/4 inch at 25 yards equals 1/8 inch at 12.5 yards.
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Bandg and Taso both a method (for half the range, use double the clicks) that essentially fits Ken's math. The key is the ratio of the known range (i.e. the 100 yards) to the new range. How to use the ratio depends on whether you want clicks per inch or inches per click--and that's where it gets tricky: one version is like similar triangles, and the other isn't. Whichever is easier for you to remember just depends on what sticks best in your mind. (If you don't do inches, then just use whatever unit it is. Does any manufacturer not use 1/4" per click?)
Here's each in terms of the 35 yard question:
Inches per click: Each click changes the angle of the scope line of sight relative to the bore line. Getting the inches per click at a new range is like asking "for the same number of clicks (i.e. the same angle), what is the "thickness" of my wedge at the range?" It's a similar triangle problem:
35/100*(1/4" per click at 100 yard)=0.0875" per click at 35 yard
Clicks per inch: This isn't simply just a similar triangle question now: we're finding the new angle:
100/35*(4 clicks per inch at 100 yard)=11.4 clicks per inch at 35 yard.
Ken's example was 1 click per quarter inch, so his math was just 100/35*(1 click per quarter inch)=2.85 clicks per quarter inch.
Note though that one of Taso's examples had a flaw in thinking. While 37.5 yards is half way between 25 and 50 yards, going with a number of clicks that is half way between the number needed at 25 and 50 isn't using the ratio correctly. At 4 clicks per inch, "half way" between 25 and 50 would lead you to 12 clicks when the ratio says it should be 100/37.5*(4 clicks/inch)=10.67 clicks per inch, ~11 clicks per inch. The mental estimate would be close, but just be aware it isn't following the rule.
Does that help anyone? Hopefully seeing both in the same posting doesn't mess you up!
Now if someone can come up with a surefire way to remember what is going to move "up" and "right" I turn the turrets in those directions...
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IF you can attach your rifle firmly to your shooting rest or IF you have a helper-
Hold on a target and fire one shot. Then place the reticle back on the target and, IF the rifle is stable and will not move, move the turrets to place the reticle on the hole made by the shot. Several IF's here but it does work for one shot zeroing.
Otherwise, 4 (or 8 depending on scope specs) clicks equals 1 inch at 100 yards equals 1/2 inch at 50 yards equals 1/4 inch at 25 yards equals 1/8 inch at 12.5 yards.
+1 That's how I do it. It doesn't always work perfectly, to many ifs. It does get you close quickly and another shot or 2 will get you dialed in.
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This is what I do...
1 click = 1/4" at 100 yards
1 click = 1/8" at 50 yards
1 click = 1/16" at 25 yards
Mathematically, this may seem like imprecise numbers, but think about the size of your pellet and these measurement differences. 1/8" is already .125", so it's going to be smaller than the diameter of your pellet. At 35 yards and using 1/8" per click, you really don't have enough precision to fine tune it within your pellet diameter per-click anyway, so worrying about the precise math isn't really needed.
Also bear in mind, that unless you have a really nice scope, it's unlikely that the clicks are actually going to be precisely what the estimate says as well. I think doing it like above helps you get into the ball park quick enough. So use 3 clicks to get into the ball park, check your POI and POA difference ( high or low ) and then move up 1 click +/- at a time until you have the POI as close to your POA as possible. The sad fact is you won't ALWAYS be able to get a precise zero.
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As Tom said "Chairgun" is your friend. Make a range card, laminate it and keep it with the gun.....
nough said.
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I know this is several months old, but couldn't help but comment on it. It always helps to know the subtensions (measurements) of your reticle in MOA (since most turrets adjust in MOA, or more accurately Shooter's MOA, i.e. IPHY), usually at the optic's highest power. I always measure mine if the manufacturer doesn't detail it in their catalogs, many don't. This way you can measure how much compensation you need without having to do much math, or (and especially) know the range. One of my 2X pistol optics has a plex reticle subtension of 17 MOA (measured), and has helped me adjust POI several times. If the POI hits say 25% of the reticle subtension from zero at any range, that's .25x17, or 4.25MOA. Simple
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Also bear in mind, that unless you have a really nice scope, it's unlikely that the clicks are actually going to be precisely what the estimate says as well. I think doing it like above helps you get into the ball park quick enough. So use 3 clicks to get into the ball park, check your POI and POA difference ( high or low ) and then move up 1 click +/- at a time until you have the POI as close to your POA as possible. The sad fact is you won't ALWAYS be able to get a precise zero.
Firmly seconded :P
With my el-Cheapo's, one time I turn a click and nothing, next time it's the same as 2 or three clicks --- and after shooting maybe it settles somewhere else. With my better scopes (UTG or Simons), maybe one click is 1/4" at 100 yards, the next 3/16 or 5/8" and math-range in accordance. I think you would be better off using the mil-dots with a little trial-and-error...
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This is what I do...
1 click = 1/4" at 100 yards
1 click = 1/8" at 50 yards
1 click = 1/16" at 25 yards
Mathematically, this may seem like imprecise numbers, but think about the size of your pellet and these measurement differences. 1/8" is already .125", so it's going to be smaller than the diameter of your pellet. At 35 yards and using 1/8" per click, you really don't have enough precision to fine tune it within your pellet diameter per-click anyway, so worrying about the precise math isn't really needed.
Also bear in mind, that unless you have a really nice scope, it's unlikely that the clicks are actually going to be precisely what the estimate says as well. I think doing it like above helps you get into the ball park quick enough. So use 3 clicks to get into the ball park, check your POI and POA difference ( high or low ) and then move up 1 click +/- at a time until you have the POI as close to your POA as possible. The sad fact is you won't ALWAYS be able to get a precise zero.
For a scope with 1/4 MOA clicks, nothing imprecise about that. You are ignoring 0.047" at 100 yards, which is about 3/64." I doubt your clicks are that accurate.
For zeroing, like others, I adjust more than I think I need, just eyeballing, and kind of iterate back and forth until I am dead on. Partly laziness and my theory is that it takes some of the lash or slop out of the mechanism.
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one must also factor in:
pellet speed and drop at the given range... :-\