Only thing I can think of is the irons bent in some way?

But if they were bent I would still be able to group it. And its fine att 25 and 50 yds.

Have you tried taking yourself out of the equation? I have a lead sled i would be willing to lend you or you can meet me at CJ and use it there.

I've tried the best I could with the bench rests that they have at efga. Although they are pretty shitty wood ones that are shot to hell.

I've tried the best I could with the bench rests that they have at efga. Although they are pretty shitty wood ones that are shot to hell.

If you want to meet up just let me know. Anything can be happening, maybe moving cheek weld, not following thru, or flinching. Each will throw you groups of much more at 100 then at 25. 

A bit about cowitness and dot/irons being "lined up" when zeroed.

 

When somebody says "Your dot should rest atop your front sight post," it's possible for them to be right and wrong at the same time.

 

It's more accurate to say that, "Presuming that you have chosen to zero both irons and your RDS to the same distance, your dot MAY end up atop your front sight post".

 

If you've zeroed your irons first, as is standard, then install the RDS and clicky-clicky on it until the dot is atop the post, that's a great way to save time/ammo in terms of getting the RDS zeroed, because it practically guarantees that you'll be on paper IOT track groups and adjust from there. And, upon shooting said group, that might even put you where you need to be.....but that's circumstance, not design.

 

Ultimate point is, the dot doesn't have to appear to rest atop the post. In fact many times it won't, and that's OK.

 

Many explanations of RDS co-witnessing are incomplete, and make many folks vapor-lock on where the dot is as a primary goal, instead of where the rounds end up. Ex: My 2 MOA T1 dot, when I establish sight alignment/sight picture with my irons, is in the same horizontal plane as the tip of my front sight post, but about 3 clicks to the right - and it's going to stay there, because each is zeroed independantly at 50/200, and that's where each hits when I use them.

 

Here's a partial answer as to why that could happen and why where the dot ends up in relation to the front post is of no real consequence:

 

Think of all the parts of the upper receiver there are between your eye and the muzzle, presuming a standard M4 type rifle. Receiver, barrel nut, barrel, FSB (assuming flat top and proper "F" marked FSB). Given the number of areas where one thing fits into/onto another from front to back on that, there's room for one sighting system to not line up in precisely the same plane as the other in relation to the line of bore. Yet, still have the gun print to the same spot, regardless of use of irons or RDS - as long as they are zeroed independently of each other.

 

Take away the FSB from that, add a FF forend and rail-or-otherwise mounted BUIS front. Is that rail installed dead-nuts-prefectly? Are the irons? Again, room for slop that may manifest itself in the dot not being perfectly atop the front sight post.

 

So, I'm not saying that your RDS dot will not end up on the tip of your front sight post, but that once you've established that both irons and RDS are zeroed as you wish if your dot isn't there, please don't rend your clothes, gnash your teeth in frustration, or have some other apoplectic fit as I've seen some do.

 

As with most other things relating to guns, quality matters, and quality costs. A gun built to the TDP in materials and manufacturing that was properly built and inspected is less likely, but not universally, to show these signs of tolerance stacking, and if they do it is likely to be much less. This is also one if the times where the false prophets of the "It's just as good as crowd" get a chance to see the truth.

believe me i understand that quality costs and i didn't skimp out on anything on my build. and i realize that the dot will not always line up exactly with the front sight post. the problem is that with or without the RDS i cant get the irons to group at 100 yards. i don't think it is the ammo. 62g m855 lc surplus out of a 1:7 14.5 bcm bfh midlength. i thought it might have been the ammo at first. it will group well at 50 but when i stretch it out to 100 i barely hit paper and cant even call my shots. all of this was nullified when i got my h-1 and it groups 3-4 inches at 100 yds with that same ammo. so it must be the sights. both troy flip up sights the rear is the dioptic. now im trying to take myself out of the equation and have someone else shoot my rifle. anyone want to put a few round down the pipe?

I might be out at EFGA this Saturday. Maybe I'll clean one of my ARs and use some good ammo to try to get some groups at 100 like you.

 

What type of ammo would you guys suggest running through a 1:9 twist barrel?

A bit about cowitness and dot/irons being "lined up" when zeroed.

 

When somebody says "Your dot should rest atop your front sight post," it's possible for them to be right and wrong at the same time.

 

It's more accurate to say that, "Presuming that you have chosen to zero both irons and your RDS to the same distance, your dot MAY end up atop your front sight post".

 

If you've zeroed your irons first, as is standard, then install the RDS and clicky-clicky on it until the dot is atop the post, that's a great way to save time/ammo in terms of getting the RDS zeroed, because it practically guarantees that you'll be on paper IOT track groups and adjust from there. And, upon shooting said group, that might even put you where you need to be.....but that's circumstance, not design.

 

Ultimate point is, the dot doesn't have to appear to rest atop the post. In fact many times it won't, and that's OK.

 

Many explanations of RDS co-witnessing are incomplete, and make many folks vapor-lock on where the dot is as a primary goal, instead of where the rounds end up. Ex: My 2 MOA T1 dot, when I establish sight alignment/sight picture with my irons, is in the same vertical plane as the tip of my front sight post, but about 3 clicks to the right - and it's going to stay there, because each is zeroed unrepentantly at 50/200, and that's where each hits when I use them.

 

Here's a partial answer as to why that could happen and why where the dot ends up in relation to the front post is of no real consequence:

 

Think of all the parts of the upper receiver there are between your eye and the muzzle, presuming a standard M4 type rifle. Receiver, barrel nut, barrel, FSB (assuming flat top and proper "F" marked FSB). Given the number of areas where one thing fits into/onto another from front to back on that, there's room for one sighting system to not line up in precisely the same plane as the other in relation to the line of bore. Yet, still have the gun print to the same spot, regardless of use of irons or RDS - as long as they are zeroed independently of each other.

 

Take away the FSB from that, add a FF forend and rail-or-otherwise mounted BUIS front. Is that rail installed dead-nuts-prefectly? Are the irons? Again, room for slop that may manifest itself in the dot not being perfectly atop the front sight post.

 

So, I'm not saying that your RDS dot will not end up on the tip of your front sight post, but that once you've established that both irons and RDS are zeroed as you wish if your dot isn't there, please don't rend your clothes, gnash your teeth in frustration, or have some other apoplectic fit as I've seen some do.

 

As with most other things relating to guns, quality matters, and quality costs. A gun built to the TDP in materials and manufacturing that was properly built and inspected is less likely, but not universally, to show these signs of tolerance stacking, and if they do it is likely to be much less. This is also one if the times where the false prophets of the "It's just as good as crowd" get a chance to see the truth.

 

 

he stated he was zeroing both at the same distance....

he stated he could not keep a group at 100 with irons..

he stated he could however keep a group at 100 with the red dot...

 

so if he lines up the irons on a co-witnessed red dot... there is no reason that I could gather where that would at least get him grouping... the rounds dont stop grouping because its irons... my suggestion was made to try to figure out what he is having an issue with... my irons and red dot run the same 50 yard zero.... if I leave my red dot on the lowest setting and look through the rear iron.. the red dot is REAL close to being right in line with the red dot...  I understand that if you zero both independently they may end up slightly different.. my suggestion was made as a starting point.. since he is having no luck at all.. 

 

I personally think he is not keeping the front sight post in the same spot in reference to the rear sight.... but thats just a guess...

My post above wasn't about quality issues, that was a related issue but not the intended crux of my post. I certainly wasn't aimed at your gear. Just wanted to point out that sometimes dot and irons identical doesn't equal them both being zeroed.

 

When is the last time you went to the eye Dr?

 

I have seen some pretty strange accuracy issues resulting from previously undiagnosed eye issues. I am talking an 8" to the left deviation at 15 yards simply by occluding the RDS and shooting using 2 eyes open with similar results using irons and closing one eye vs 2 eyes open and an unoccluded RDS. It was ultimately raced back to an astigmatism in the shooters Left eye - he was right handed shooter.

i was just at the eye doctor for a check up from my PRK surgery back in may. its definitely not my eyes. im starting to think that the dioptic rear is the cause. the diamond disappears as its supposed to but i'm just completely not used to it. with my garand i can still see the rear ring for reference so i can center the front post. with the dioptic i can't.

I prefer a 50/200 yard zero. (Green trace on graph below)

Most of the higher speed teams use it at it is the most versatile zero out there for DA/CQB/FISHing. It is very simple to use, simply account for mechanical offset when taking a high percentage shot by aiming high 2.5"-2" inside of 10 yards, 1.5" high at 15 yards and around 1" at 25 yards. Everything else from 0-215 yards is +/- 3" from point of aim and requires no holdover adjustments.

Not sure why my iPad won't paste the trajectory chart above. But I was at the 50yd range today working on my zero and I have this question. How come on these trajectory charts the bullet starts at MINUS 2 inches? Is that because my bore is two inches below my sights? Also, in some of those chart I've seen they show a figure of a barrel, and that barrel is tilted up. Is my barrel actually tilting up slightly when looking down my sights? When I see trajectory charts with bullet rising I just assumed it was a ballistic thing, is it because the barrel is up?

 

Like gor example below shows the barrel up:

 

http://aesirtraining.com/home/wp-content/uploads/2011/05/Trajectory.jpg

The way I understand it: obviously the barrel is straight. The front and back sites are at different heights above bore ( front is shorter). If you're looking straight through the sights then the barrel will be angled up slightly. So relative to the sights the barrel is angled. Relative to the rest of the gun it's not.

Bullets do not rise when they leave the barrel. They are aimed in a ballistic trajectory by the particular alignment of the sights. It you had the sights aligned so that the line of sight was exactly parallel to the barrel, and the barrel was perfectly parallel to the ground, the bullets path would start to "fall" the instant it left the barrel.

 

You are correct, the ballistic tables show a -2 at 0 yards because of the boreline/sightline discrepancy built into a rifle with an inline stock. This difference is commonly known as "mechanical offset". It is approx. 2.5" in a standard AR setup. Shooting at 25 yards or more this ain't a big deal, the ballistic flight path of the projectile will have a much greater influence over the flight path of the round fired. Inside of 25 yards, when taking a high percentage shot, it is crucial to success.

 

ETA: The link you have above is actually pretty good showing the relationship between the shooter, sight line, bore line, barrel, sights, and flight of the projectile.

Edited January 12, 201412 yr by High Exposure

On a related note, am I the only person who zero's their optic and irons for different distances? 

Yes?

Well at least I'm unique.

 

The actual reason is that with irons I prefer to dot the "i" as I find the front post to much at longer distances, so a 300y zero works well for that, as pretty much everything is going to be high before 300y, and I zero my optics for 200.

On a related note, am I the only person who zero's their optic and irons for different distances?

 

wouldnt that get confusing with your holdovers and what to use at what distance?

That's not the biggest problem, really. Keep track of two trajectories is not that hard.  The annoying problem is doing two different zero procedures whenever you change ammo or something.

Same 50/100/300 make adjustments as required and take notes to make sure youre hitting correct I check poi to adjust. Ill be going from 100 to 300 tomorrow to make my mil adjustments on 556 and ar10 168 grain. There is no reason you cant hit 3 or so moa with 556/223 after adjustments with a quality weapon with scope at 300 But for cqb 50yd dialed in is good enough. If you shoot enough kentucky windage is king. It means you own and know your rifle. Cheers ar's for all.

I can't believe i always thought the bullets rose because of rifling or something.

 

Now all this zeroing stuff is making sense to me