I am having trouble ranging with my MOA reticle. Following the formulas, but getting the wrong ranges. I am using known target sizes with known distances and getting yardage numbers that are way too big. Any suggestions?
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Ranging problems with Viper PST
- Thread starter tactrainer
- Start date
Re: Ranging problems with Viper PST
What formula are you using?
Is your reticle MOA or IPHY or something else?
Have you checked it?
How precise are you on your visual measurements?
Need info to answer correctly.
Cheers,
Doc
What formula are you using?
Is your reticle MOA or IPHY or something else?
Have you checked it?
How precise are you on your visual measurements?
Need info to answer correctly.
Cheers,
Doc
Re: Ranging problems with Viper PST
I am using the formula that Vortex recommended...
Known target size in inches/Measured MOA x 95.5
Reticle is MOA
I have questioned Vortex and they assured me the reticle was spot on, but how would you recommend I check it?
I am using the formula that Vortex recommended...
Known target size in inches/Measured MOA x 95.5
Reticle is MOA
I have questioned Vortex and they assured me the reticle was spot on, but how would you recommend I check it?
Re: Ranging problems with Viper PST
Are you measuring the target against the proper dimensions? Say the target is 20" wide and 40" tall. If you measure the target vertically with the reticle then you have to use the size in inches (40).
BTW you take the target size in inches x 95.5 then divide that number by the MOA measurement.
Are you measuring the target against the proper dimensions? Say the target is 20" wide and 40" tall. If you measure the target vertically with the reticle then you have to use the size in inches (40).
BTW you take the target size in inches x 95.5 then divide that number by the MOA measurement.
Re: Ranging problems with Viper PST
I have been measuring as you described. I measured a know 8 inch target at a known 100 yard distance and my calculations gave me a distance of 137 yards. Something I am doing is goofed up.
I have been measuring as you described. I measured a know 8 inch target at a known 100 yard distance and my calculations gave me a distance of 137 yards. Something I am doing is goofed up.
Re: Ranging problems with Viper PST
Again....
BTW you take the target size in inches x 95.5 then divide that number by the MOA measurement.
(Size or target in inches X 95.5) / MOA
Again....
BTW you take the target size in inches x 95.5 then divide that number by the MOA measurement.
(Size or target in inches X 95.5) / MOA
Re: Ranging problems with Viper PST
Is your scope FFP? If not, are you using the correct magnification for ranging? SFP scopes only range correctly at a certain magnification.
Is your scope FFP? If not, are you using the correct magnification for ranging? SFP scopes only range correctly at a certain magnification.
Re: Ranging problems with Viper PST
My first thought is that you might have the SFP version and not the FFP one ?
Which version is it ? As the SFP won't be correct at all magnifications.
Slafav and I apparently think the same...he just types faster lol.
My first thought is that you might have the SFP version and not the FFP one ?
Which version is it ? As the SFP won't be correct at all magnifications.
Slafav and I apparently think the same...he just types faster lol.
Re: Ranging problems with Viper PST
The SFP scopes have numbers on the power ring. For example my 6-24 has a 1 on the 24x for 1 moa, a 2 on the 12x, 3 on the 8x and 4 on the 6x. Make sure you have your power ring in the proper place for the formula you are using. Mine is Dead On.
The SFP scopes have numbers on the power ring. For example my 6-24 has a 1 on the 24x for 1 moa, a 2 on the 12x, 3 on the 8x and 4 on the 6x. Make sure you have your power ring in the proper place for the formula you are using. Mine is Dead On.
Re: Ranging problems with Viper PST
I would make sure your reading of the mils is precise because you are reading 5.577-5.6 moa in your scope which gives you the 137 range you should be reading more like 7.64 moa assuming I did all my math right. I would verify you are getting the correct MOA readings and its usually easiest to range at your maximum zoom as long as you can still view the object to be ranged at that magnification.
I would make sure your reading of the mils is precise because you are reading 5.577-5.6 moa in your scope which gives you the 137 range you should be reading more like 7.64 moa assuming I did all my math right. I would verify you are getting the correct MOA readings and its usually easiest to range at your maximum zoom as long as you can still view the object to be ranged at that magnification.
Re: Ranging problems with Viper PST
tactrainer,
A couple of things:
You stated "a known 100 yds". Did you actually measure the distance from the turrets to the target with a tape? You can't depend on the "local range" or LRFs. (BTW, I learned this one from Lindy when running a "box test".)
Regarding the "target" size, you might try a yard stick or other precision measuring device (like a surveyor uses a rod) and try some different size "targets". It might be easier to select and read "even" MOA increments on your scope, then read the height of target on the stick.
Slight errors on both distance and MOA reading would impact the desired outcome.
Good luck,
Kevin
tactrainer,
A couple of things:
You stated "a known 100 yds". Did you actually measure the distance from the turrets to the target with a tape? You can't depend on the "local range" or LRFs. (BTW, I learned this one from Lindy when running a "box test".)
Regarding the "target" size, you might try a yard stick or other precision measuring device (like a surveyor uses a rod) and try some different size "targets". It might be easier to select and read "even" MOA increments on your scope, then read the height of target on the stick.
Slight errors on both distance and MOA reading would impact the desired outcome.
Good luck,
Kevin
Re: Ranging problems with Viper PST
Why the frik would you do it with mills, the scope is MOA/MOA and he measured the target & range in inch/yards respectively. That is something that will get people confused, and is an unnecessary source of error. MILS have nothing to do with this question.
Since the scope is FFP, we should assume for diagnostic purposes that the error lies elsewhere. If I were the OP, i'd start from scratch. You need to make sure that there is not an error in some other dimension here. Start with these:
*How did you measure the known distance to target? If you did it with a rangefinder, that could be the issue right there. LRF, especially the cheaper ones, can have a large beam divergence even at fairly close ranges. This means it may have been hitting something else near the target. If this is an outdoor range or just impromptu spot in the countryside, make sure you are not accidentally ranging brush, rocks, etc. Also, if the terrain is not level your rangefinder will give you an incorrect value if it is not a model that can adjust for angle of trajectory. You need to use one that gives a true ballistic solution, or be aware and convert your readout with an angle cosine formula based on a measured angle (via ACI, etc.).
*If you were shooting an existing emplaced target, like at a club range, I would take the time to measure it out with a tape and make sure the distance is actually what they said it is. Perhaps it is a bit off, or perhaps your shooting position was adjusted from where they measured the distance initially? Try to be as accurate as possible here with the tape measure. Get someone to help if necessary.
*If the error is not found in the "known" range, then remeasure your target and see if you made a mistake.
*If that's not it, make sure you are using the reticle correctly. Consult the product literature for the accurate dimensions of the reticle's scalar marks. DO NOT ASSUME that the distance between one set of marks is 1 MOA, it's not. On the PST's reticle it is as shown in this picture (courtesy of vortex):
Note that up to the ten MOA mark the subtensions are (2) MOA, after which they are (5) MOA. Make sure your math is right.
*Make sure you are using the forumla as KNIGHT posted it. What you initially posted is wrong, and it does make a difference in the math.
*Also remember that 1 moa @ 100 yards is actually 1.05 inches... it's a negligable difference at short range, but does contribute to a 5% error which needs to be corrected for @ longer ranges. If you dialed a shooting solution @ 100yds. for an uncorrected measurement, it would still likely be close enough for a hit, but be aware it's not correct mathematically.
I think this is where your error lies, as evidenced by this solution:
Formula: [known target size * 95.5] / [measured MOA corrected for 5% error] = range in yards
so: [8*95.5] / [8moa/1.05] = range in yards
thus: [764]/[7.62]= 100.26 yards
Why the frik would you do it with mills, the scope is MOA/MOA and he measured the target & range in inch/yards respectively. That is something that will get people confused, and is an unnecessary source of error. MILS have nothing to do with this question.
Since the scope is FFP, we should assume for diagnostic purposes that the error lies elsewhere. If I were the OP, i'd start from scratch. You need to make sure that there is not an error in some other dimension here. Start with these:
*How did you measure the known distance to target? If you did it with a rangefinder, that could be the issue right there. LRF, especially the cheaper ones, can have a large beam divergence even at fairly close ranges. This means it may have been hitting something else near the target. If this is an outdoor range or just impromptu spot in the countryside, make sure you are not accidentally ranging brush, rocks, etc. Also, if the terrain is not level your rangefinder will give you an incorrect value if it is not a model that can adjust for angle of trajectory. You need to use one that gives a true ballistic solution, or be aware and convert your readout with an angle cosine formula based on a measured angle (via ACI, etc.).
*If you were shooting an existing emplaced target, like at a club range, I would take the time to measure it out with a tape and make sure the distance is actually what they said it is. Perhaps it is a bit off, or perhaps your shooting position was adjusted from where they measured the distance initially? Try to be as accurate as possible here with the tape measure. Get someone to help if necessary.
*If the error is not found in the "known" range, then remeasure your target and see if you made a mistake.
*If that's not it, make sure you are using the reticle correctly. Consult the product literature for the accurate dimensions of the reticle's scalar marks. DO NOT ASSUME that the distance between one set of marks is 1 MOA, it's not. On the PST's reticle it is as shown in this picture (courtesy of vortex):
Note that up to the ten MOA mark the subtensions are (2) MOA, after which they are (5) MOA. Make sure your math is right.
*Make sure you are using the forumla as KNIGHT posted it. What you initially posted is wrong, and it does make a difference in the math.
*Also remember that 1 moa @ 100 yards is actually 1.05 inches... it's a negligable difference at short range, but does contribute to a 5% error which needs to be corrected for @ longer ranges. If you dialed a shooting solution @ 100yds. for an uncorrected measurement, it would still likely be close enough for a hit, but be aware it's not correct mathematically.
I think this is where your error lies, as evidenced by this solution:
Formula: [known target size * 95.5] / [measured MOA corrected for 5% error] = range in yards
so: [8*95.5] / [8moa/1.05] = range in yards
thus: [764]/[7.62]= 100.26 yards
Re: Ranging problems with Viper PST
As was mentioned above you need to have a measured 100 yards to precisely calibrate your optic. That being said a 37 yard error is pretty fricking huge so you could get away with being off by a yard or two just to see what is going on.
Take a 21" target and set it at your 100 yard mark. Look through your scope. It should fit exactly between your 10 MOA up and 10 MOA down marks. If it doesn't your scope is jacked.
If you turn the power ring at it suddenly fits, you either have a SFP optic or your scope is jacked.
If it does fit your math is wrong.
Size of the target in inches (21) * 95.5 (= 2005.5) / MOA in your optic (20)
21*95.5/20 = 100.275 yards
The .275 is because of the .047.... which is in this case rounded to the nearest 1/2 inch because you cannot tell the difference between 21" and 20.94" at 100 yards.
If your going to check your optic do it with something that comes out even in your reticle not something that has you guessing which 1/4 of the clear space between stadia you're in.
An 8" target at 100 yards should subtend about 7.6 MOA, to get it to range 137 yards it would be about 5.5 MOA in your scope. HUGE difference.
Cheers,
Doc
As was mentioned above you need to have a measured 100 yards to precisely calibrate your optic. That being said a 37 yard error is pretty fricking huge so you could get away with being off by a yard or two just to see what is going on.
Take a 21" target and set it at your 100 yard mark. Look through your scope. It should fit exactly between your 10 MOA up and 10 MOA down marks. If it doesn't your scope is jacked.
If you turn the power ring at it suddenly fits, you either have a SFP optic or your scope is jacked.
If it does fit your math is wrong.
Size of the target in inches (21) * 95.5 (= 2005.5) / MOA in your optic (20)
21*95.5/20 = 100.275 yards
The .275 is because of the .047.... which is in this case rounded to the nearest 1/2 inch because you cannot tell the difference between 21" and 20.94" at 100 yards.
If your going to check your optic do it with something that comes out even in your reticle not something that has you guessing which 1/4 of the clear space between stadia you're in.
An 8" target at 100 yards should subtend about 7.6 MOA, to get it to range 137 yards it would be about 5.5 MOA in your scope. HUGE difference.
Cheers,
Doc
Re: Ranging problems with Viper PST
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CallOfDuty#1</div><div class="ubbcode-body">U could probably do it with mils </div></div>
Back to your video game CallOfDuty#1...
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CallOfDuty#1</div><div class="ubbcode-body">U could probably do it with mils </div></div>
Back to your video game CallOfDuty#1...
Re: Ranging problems with Viper PST
Thanks to all who have taken the time to help me out. I will try your suggestions next time I can get some free time and daylight.
Thanks to all who have taken the time to help me out. I will try your suggestions next time I can get some free time and daylight.
Re: Ranging problems with Viper PST
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: High Binder</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CallOfDuty#1</div><div class="ubbcode-body">U could probably do it with mils </div></div>
Back to your video game CallOfDuty#1... </div></div>
Track Call of Duty's posts.....they are all lame shit like this. Hopefully he isn't in a race to 100 in order to sell something to someone. He'll post up a Barrett 50 cal and sell it to someone for $10,000 and then send him his X-Box memory card in the mail.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: High Binder</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: CallOfDuty#1</div><div class="ubbcode-body">U could probably do it with mils </div></div>
Back to your video game CallOfDuty#1... </div></div>
Track Call of Duty's posts.....they are all lame shit like this. Hopefully he isn't in a race to 100 in order to sell something to someone. He'll post up a Barrett 50 cal and sell it to someone for $10,000 and then send him his X-Box memory card in the mail.
