[Belt Fed]

Never dealt with these type of sights and have a question.

Are these things designed to be near spot on once a distance has been set?

Example:
I have it set to 1 for 100 yards. If i successfully sight in at this distance, when I rotate the drum to 200, will the POI be near center?

I believe I am mistaken, and if that's the case, whats the proper sight in procedure for these things?

Here's a pic of em if anyone's curious.

 

[tacman605]

That is my understanding of it. You zero and then dial in the sight for the yardage. There will be some fine tuning but this will give you a battle sight zero for the lack of a better phrase.

 

[ullie]

Are these things designed to be near spot on once a distance has been set?

Example:
I have it set to 1 for 100 yards. If i successfully sight in at this distance, when I rotate the drum to 200, will the POI be near center?

...once zeroed with the "correct" ammunition the range marking will be perserved to be "near" spot on...that particular diopter "appears" to be a Swiss rear diopter for the 55x series of rifles...

...there are several ways you can zero her...

...first off...when using a diopter sighting system...you need to " ensure that the periphery of the foresight tunnel and the diopter aperture are concentric."...the front sight post should be roughly in the center of the foresight tunnel in order to get the proper sight picture...likewise...as with most diopter systems...you shoot POA=POI with the front sight post's top "center over target"...all elevation adjustments to zero the weapon are made with the rear sight only...the 100 meter setting is your CQB setting...

...if i remember correctly...these particular diopters are calibrated for the GP 90 cartrage...and will work "relatively" well with ammunition with a muzzle velosity of "roughly" 3000 fps and that have a ballistic coefficient of about .330...the greater the deviation from these perameters...the larger your striike error will become in elevation...especially as you increase the range...

...one way to zero them would be to initially use your "near zero" to establish a rough "far zero"...and then "always" confirm your far zero at the appropiate range...ie at crossover...

...it is preferable to zero the weapon at 300 meters...POA=POI...using the 300 meter aperature...to start...set up your target at ~ 33 meters and fire POA=POI...then move your target out to 300 meters and confirm...adjust as necessary... you will have to adjust your elevation and most probably your windage...but less on the windage...after you zero at 300 meters...leave it there...

...you can also shoot POA=POI @ 50 "yards" using the 200 meter apperature...same as before...confirm at 200 "meters"...you "may" be a little off at 300 meters using this method...but will "probably" shoot more accurately at closer ranges "depending" on the ammunition you will be using...and it's velosity and BC...at short ranges the velosity and ballistic coefficient won't be so much an issue as it will at longer ranges...

...to "half ass" perserve the range markings on your rear diopter...i recomend...to start with...using a FMJ lead projectile of between 60 and 64 grains developing a muzzle velosity of roughly 3000 fps...this would mean that the barrel length will need to be at least 16 inches or longer in most cases to get the best results...

...to give you more flexability in the choice of your ammunition...i would zero @ 50 "yards" POA=POI as before...adjust and confirm @ 200 "meters"....with the ammunition you will be using..and hold over/under as needed @ 300/400 yards...using the 200 meter aperature...you never know though...the 300/400 meter aperature may bring you close...doesn't hurt to try them...

...i hope some of this makes sense...

 

[Belt Fed]

Wow, thanks for all of that. You answered everything, including future questions.

 

[Belt Fed]

Actually I do have one question involving ranges to sight in.

Is it incorrect to sight in at that range for the initial sight in? If so, why?

 

[ullie]

Is it incorrect to sight in at that range for the initial sight in? If so, why?

...why would it be incorrect ?...you sight in using a "near zero" just to get you on paper...and then make the final adjustments at a longer range...using a near zero gets you half way there...so that at longer ranges you'll at least be "somewhere" on the target which will enable you to make the final adjustments...

...when you use any sights that are capable of compensating for range...you should zero the weapon to preserve the range markings on the sight "if possible"...or ignore the range markings and zero the weapon for the most utilitarian "point blank range" based on your primary intended use of the weapon...the diopters used on assualt rifles are not target sights...and are designed to give you a good "hit probability" out to their design limits when used properly in concert with the barrel length / sight radius that they are designed for when using the ammunition that they are calibrated for...

...when you sight down your rifle...ie...your point of aim...you have a linier line of sight to the target...your intended point of impact...the actual flight of the bullet's trajectory is not in a stright line...but curved...your sights are above the bore axis....because "gravity" affects the bullet as soon as it leaves the muzzle...pulling it downwards...you are actually firing the weapon with the barrel slightly inclined upwards...the degree of inclination determines your near and far zero...

...the near zero is where the bullets path first crosses your line of sight as it "raises" above it...your far zero is where the bullet again crosses your line of sight as the bullet "decends" below it...

...the center of each apperature is a different height above the bore axis...the number 3 apperature sits higher than the number 2...for example...and the number 4 apperature sits highter than the number 3...as you go from the number two apperature setting to the number 3 setting...you raise the degree of inclination of the barrel...placing the "near zero" closer to the shooter and placing the "far zero" further out...doing this also increases your "mid range trajectory" ...or the height the bullet will be above your line of sight at it's highest point...based on your zero distance with a specific weapon and ammunition combination...and this is predicated on having a "correct and consistant" sight picture...as mentioned in my above reply...

...your "near zero" gets you "on paper" with a predictable crossover at a particular range...at which time you should make the final elevation adjustments...and "if" the diopter is correctly calibrated for a specific weapon and ammunition combination...ie...based on such variables as exit velosity...the projectiles ballistic co-efficient and the weapons sight radious...and there are others...you should be able to "dial in" the range based on the diopter range markings and hit your target with a relatively high degree of predictability at range...

...when sighting in an assualt rifle using diopters...the final elevation adjustment should be made using the 300 meter apperature and shooting POA=POI at a target set at 300 meters...this will "generally" give you your best "point blank range" for "most" combat applications...even though you would normally leave you diopter set for close quarters......for recreational use...i would recomend making your final adjustments at 200 meters using the 200 meter apperature...which will still perserve your 300 meter setting to a great degree...as long as the ammunition is compatable with the weapon system...

...as a recreational shooter you will most likely be shooting "marked distances" of 200 yards or less using your irons...so that to be able to shoot more accurately at these ranges...i would suggest you zero your weapon using the a near zero of 50 "yards" to get you on paper while using the number 2 apperature...and then adjust your elevation when shooting @ 200 "meters" if necessary...again using the number two apperature...if you don't have a 50 yard range...you can use 25 yards...adjust your elevation so that you print ~ 1 1/4 inches below your POI @ 25 yards using the number 2 apperature and then confirm @ 50 and then confirm / adjust @ 200 "meters"...

 

[ullie]

...this is the correct sight picture when using a diopter system...notice the vertical and horizontal lines...the post should be centered as pictured...POI=POA...