View Full Version : Front sight on AR: What is the difference of 3mm in height?

09-18-2012, 6:57 PM
On a 14.x rifle, what is the difference of 3mm in front sight height?

My guess is that it is a lot?

I started to build a 14.x with a standard height railed gas block (not hand guard height). I bought a couple of different detachable front sights, both are supposed to be for gas block height.

Comparing them side-by-side mounted on a rail, the tip of the sight between the two has a height difference of 3mm. I know they are adjustable, but I'm not sure if it's adjustable by 3mm.


09-18-2012, 7:16 PM
1 mm = .0395"
3mm + .120" or almost 1/8"- .125"

09-18-2012, 7:27 PM
1 mm = .0395"
3mm + .120" or almost 1/8"- .125"

LOL thanks...

09-18-2012, 7:53 PM
It sounds like you might have got one rail height front sight.

Try clamping the tall one right in front of the rear sight (assuming a railed upper) and see if the post is about the the same height as the aperture. If it is, it's a rail height front sight.

If you have a railed handguard (that isn't angled up or down), you could move your rear sight right behind your gas block to do a similar test.

09-19-2012, 7:56 AM
What is the sight radius? Referring to 6mmintl's math, you have an almost .125" difference. With a 30" sight radius, .008" = approx 1 MOA. You can ratio it out from there and get reasonably close.

09-19-2012, 7:43 PM
Thanks guys. I later realized that it was kind of a silly [dumb] question. In any case, I sent my upper/kit back (another story) so I don't even have an AR to play with. Just staring at all the parts I got...