858 issue that I can't explain

[Satain]

Can some one enlighten me to this situation.
A friend from the range ask me if I had a Bushnell TRS-25 in my handguards could I co-witness.
So today I went home and slapped on my $80 USD optic and proceeded to move the rear sight up all the way. Lord behold I could clearly see my front post sight and also it looks like as if I were to be shooting it via iron sight. But I started laughing cuz it was at the 800 setting. But then it did look like the rifle was level. So I did some buba'ing and set up my rifle on my make shift bench and as you can see from the photo's the rifle is completely level although the rear sight is cranked to the 800 meter setting.

Now my question's are...

1. This must be because it is on my short 12" barrel and would not work with my 19" barrel. Right?
2. If the rifle is level this means that the bullet would shoot some what straight for a short distance before it drops. Right?
3. This classify as a lower 1/3 co-witness. Even if the rear sight is on the highest setting?
4. If I crank up my front post in theory I could lower my rear sight. Right?

 

[dweenz]

1. the angle has to change on a longer sight radius so yes it would look different on a 19 inch barrel basic trigonometry.
2.if the barrel is dead level yes the bullet would travel straight before dropping the arcing of a bullet is by setting your sights to aim the barrel at a slight incline.
3.i would think it is not a good co-witness because the rifle is basically useless at that distance but technically it is a co-witness.
4. yes up on the front means down on the back. look thru the scope with it set down at 100 m marking can you see the hood of the front sight?if yes then you could maybe extend the front post to that area.


what kind of rail is it an nea upper?

 

[Satain]

Nope BC Tac one.
I am going to put all this gear on my non-restricted 858 and crank the front post sight up as far as it will go and see if it will work on that one too. But what the kicker for me was that it was completely level and that setting. witch means (of course in theroy) it should be bang on @ 25 meters.

 

[Hokus Grey]

As far as I know, only NEA's handguards will allow you to co-witness with a low profile red dot.

 

[dweenz]

if it is level and you shoot at 25 yards the bullet impact should be low about whatever distance from the bore to the center of optic.

point being if you set your sights dead level to the barrel you will not have a good distance shot at 100 yards the bullet is dropping another 3 inches so if your optic is 2 inches above the barrel you will be hitting 5 inches low at 100 and dropping off quickly from there. look at the bullet drop numbers not the elevations will tell you what a bullet shot out level will do.

don't try and do a co-witness with bc tactical upper unless you are going with buis. which would require nea stock adapter and barrel rail clamp.

 

[Satain]

if it is level and you shoot at 25 yards the bullet impact should be low about whatever distance from the bore to the center of optic.

point being if you set your sights dead level to the barrel you will not have a good distance shot at 100 yards the bullet is dropping another 3 inches so if your optic is 2 inches above the barrel you will be hitting 5 inches low at 100 and dropping off quickly from there. look at the bullet drop numbers not the elevations will tell you what a bullet shot out level will do.

don't try and do a co-witness with bc tactical upper unless you are going with buis. which would require nea stock adapter and barrel rail clamp.

So I did this...
Red dot @ 100 meter's and irons at 25 meter's and I feel that I am preaty much covered now. This is what my sight picture looks like;

Oh ya another thing that I just figured out. The T1 micro's actually sit higher than the TRS-25's.
Here is a pic of what I mean;

As you can notice I can have an extra LaRue clip were as with the TRS-25 I can not even have it there;

Don't know if I like this sight picture so much. I think I might have to return back to my Insight MRDS set-up. As I find the target acquizition process way easier. But I thought that some people would just like to know.

 

[North Eastern Arms]

Or just swap out the upper.

 

[dweenz]

Or just swap out the upper.