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AR-10A4 UNEVEN GAS BLOCK PICATINNY? (Read 5082 times)

HUCKLEBUCK

AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« on: June 09, 2013, 01:37:59 PM »
Can someone explain what armalite means when they hype the "clamping gas block mount that allows the front sight to be rotated to zero, which assures the rear sight is centered and full left and right windage movement is available when shooting in strong winds"?

I have this rifle and I'm looking into sights and don't fully understand what they're saying.

How does rotating the front sight make the rear sight centered?

How could loosening the gas block hex screws to rotate the block not affect the function of the gas system or even screw it up?

And for the record, why the hell would armalite make a flat top model with non continuous picatinnys for the front and rear sights and NOT make them level, which requires insanely difficult web research to find front sights that are made "elevated" to compensate for the gas block mount being .34" lower than the rear!!!!!??? Yes armalite sells them for an arm and a leg!

Why the hell don't they just make them with block picatinny top just .34" thicker to make it level with the rear, this way the consumer can mount any sights rear and front that they like???? No, that would make friggin sense!!!

One more thing on that note.....so people say you have to get special front sights made for the lower gas block mount (GG&G, DIAMONDHEAD, MI) otherwise you can't sight the rifle. But this isn't true right, it just means at a close say 50 or 100 yds "zeroed" you'd shoot a little high since the rear sight is 'raised' relative to the front. So I could use any sights, I'd just have to compensate for the false high shooting, which i really wouldnt notice except for long distance target shooting, right? 

Or am I just trying to rationalize using inappropriate sights to spite my rifle's uneven rails?

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moosed

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Re: AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« Reply #1 on: June 09, 2013, 05:22:35 PM »
I believe it means: if you have ever zeroed a rifle with the rear sight set halfway between center and the left or right stop, this feature will make you very happy. 

In a perfect world, every rifle would zero with the rear sight centered -- dead on bulls eye with no left/right adjustment.  In reality, it's impossible for every rifle to be assembled with perfectly aligned sights mechanically.  Therefore, the windage for some rifles will be centered at zero, but many others will be left or right, and to varying degrees.

I have this issue on my Colt.  Because the rear sight is 4 clicks to the left at zero, it causes the BUIS to align slightly left of center in my red dot sight when co-witnessing.    I would have thought the red dot would stay in the center of the scope.  What I learned is, when the BUIS are not perfectly in line with the rail, the BUIS will be off-center in the red dot.

I would enjoy having the ability to move the front sight slightly to bring the muzzle more left and in line with the rear sight.  In effect, I would be using the front sight to correct for windage instead of the rear.  Then my sights would be in the center at zero, and the red dot would co-witness in the center of the scope.

Hope that clears up the sighting question.
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gsmgc

Re: AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« Reply #2 on: June 09, 2013, 06:14:32 PM »
There are a lot of manufacturers that make picatinney gas blocks that are lower than the flat top of the receiver.
Enough so that sight manufacturers make front sights to remedy this problem.
Why this is the case, I have know idea.

Do you have a rail type hand guard, or the plastic type?

I never heard of rotating the gas block to help achieve zero before, but that is just me.
You may run into other problems by doing this, and seems a bit of a hassle.

It is a .308, so you will probably be running a long distance scope, and wont be using BUIS anyway.

Seems like you have a few options, but utilizing a higher front sight is probably the cheapest/easiest way to go, or just compensate manually.
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HUCKLEBUCK

Re: AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« Reply #3 on: June 09, 2013, 06:17:17 PM »
yeah man. that helps a lot. especially since i am setting up the 10 woth what you describe: buis and a red dot. so not i wont get bugged if the dot is off (even thought i can correct this as you said).

but i had another questions: they call it clamping block that can be "rotated".  i get it now after you explained but im not clear on how a rotating mount would be best for this.

 in other words, i would guess that what would be best is a front sight that can be 'micro' adjusted as far as its side-to-side position, so that the block mount stays put but the site itself can be adjusted. 

it seems that unclamping a gas block mount to do the adjustment you describe would open one up to potentially screwing up the gas system operation.....a serious potential pitfall to accept in order to deal with a relatively trivial inconvenience (more of an issue with the red dot added as you say).

i know from what you describe you should only have to unclamp the block and do this once but there are no marks on it to assist in the adjustment.  so what would i have to do...unclamp, move, reclamp, resight, shoot.....and repeat this until the rear is at the midpoint windage at zero?

thats seems to be a seriously difficult and inexact process. is that what you think id have to do?

and also dont you think messing with the gas block so many times is risky?

i dont know why they dont take advantage of the 'adjustable' front sight gas block by doing it at the factory when they test shoot the rifle. this way its done once and for all - until you modify the forend or something.

i appreciate the help again.



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hnl.flyboy

Re: AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« Reply #4 on: June 09, 2013, 06:22:44 PM »
I had a rifle something like this.  If I had to adjust my front sight because it wasn't aligned well with the rear sight, I could loosen the Front Sight Block and tap it left or right with a hammer till it shot near center, then tightened the block back down.  One to four clicks either way was close enough to zero.
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moosed

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Re: AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« Reply #5 on: June 09, 2013, 06:32:07 PM »
Quote from: HUCKLEBUCK on June 09, 2013, 06:17:17 PM
....
it seems that unclamping a gas block mount to do the adjustment you describe would open one up to potentially screwing up the gas system operation.....a serious potential pitfall to accept in order to deal with a relatively trivial inconvenience (more of an issue with the red dot added as you say).

i know from what you describe you should only have to unclamp the block and do this once but there are no marks on it to assist in the adjustment.  so what would i have to do...unclamp, move, reclamp, resight, shoot.....and repeat this until the rear is at the midpoint windage at zero?

thats seems to be a seriously difficult and inexact process. is that what you think id have to do?

and also dont you think messing with the gas block so many times is risky?

i dont know why they dont take advantage of the 'adjustable' front sight gas block by doing it at the factory when they test shoot the rifle. this way its done once and for all - until you modify the forend or something.
....

For more details, you should consider calling the manufacturer, or find a gunsmith who has experience with this firearm.  You're looking for some very specific answers that require either direct manufacturing knowledge or hands-on experience,  There may be a very simple process for aligning the front sight while zeroing.  Without doing  the research (which I'm sure you are also capable of doing), I couldn't even start to describe the procedure.

Good luck!   :shaka:
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HUCKLEBUCK

Re: AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« Reply #6 on: June 09, 2013, 11:38:07 PM »
amazingly, even though every person who bought one of these must have the same questions, there are no blogs, fora, youtube vids, or any other source that covers the procedure; amazing since you can find the most obscure esoteric info and procedures on ar types in nearly every format - but not this topic!

also, i emailed armalite's technical dept and they sent an auto email apologizing for not being able to respond to emails due to high volume - so thats why i came here.

anyways, thanks guys....preciate the help. 
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moosed

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Re: AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« Reply #7 on: June 10, 2013, 12:15:44 AM »
Quote
15-7.  QUESTION:  The front sight base of my rifle has two screws running through it below the barrel.  What are they for?

 ANSWER:  They are used on National Match, and occasionally on other rifles, to allow the owner to zero the front sight.  Normal manufacturing tolerances may result in the rear sight being somewhat off center when the rifle is zeroed.  ArmaLite’s exclusive clamp style front sight base allows the owner to zero the front sight for windage, and thus to center the rear sight. The military refers to this step as zeroing the rifle’s “mechanical zero.”
To do so, put the rear sight in the center of the rear sight base.  Fire a three-shot group.  To adjust the next shot group to the left, shift the front sight to the right (and visa versa).  Tighten the clamping screws and finish zeroing in the normal manner using the windage knob of the rear sight.  Elevation is adjusted normally.

The clamping screws also allow the sight base to closely seal the gases that pass through the base to the gas tube, this improving the power of the operating system.

http://www.armalite.com/Categories.aspx?Category=538b8c3c-6710-4282-839f-fb5caf8043a3#gt
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hnl.flyboy

Re: AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« Reply #8 on: June 10, 2013, 05:47:14 AM »
^ Just as I said earlier  ;D
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HUCKLEBUCK

Re: AR-10A4 UNEVEN GAS BLOCK PICATINNY?
« Reply #9 on: June 10, 2013, 09:02:17 PM »
thanks man
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