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4/22/2012 4:53:37 PM EDT

I went from a rifle-length YHM to a mid-length Troy Alpha. Very nice. But my zero seems to have changed substantially. I had to adjust the ACOG 20 clicks down just to be on target at 100 yards.

In general, does going from one FF forearm to another change the zero?  

4/22/2012 4:56:18 PM EDT
[#1]
Your barrel torque changed. Any time you swap rails you may see a change in impact.
4/22/2012 4:56:27 PM EDT
[#2]
Did you have to loosen and re-tighten or change the barrel nut?

If so, there you go.
4/22/2012 5:08:29 PM EDT
[#3]
I had it done for me but I watched the whole thing. Yeah, the barrel nut came loose. They use different mounting methods.
4/22/2012 7:09:47 PM EDT
[#4]
Quoted:
I had it done for me but I watched the whole thing. Yeah, the barrel nut came loose. They use different mounting methods.


Bingo!!!
4/23/2012 6:06:10 AM EDT
[#5]
When I changed to a FF I had to move 18 clicks up (~9 inches at 150 yards). Scope never left the rifle.

Edit. My calculations are if the barrel is now better while shooting prone off a bipod by 1/32" , just a guess, on a 20" barrel that would move my shot ~8.78" in one direction. Subtracting out all other variables. Which it seemed to do.
4/23/2012 9:05:41 AM EDT
[#6]
20 clicks sound excessive to me on any sighting device.  Then again, if the old set up took ten clicks in the other direction, then you simply brought the device back to what could considered its mechanical zero, and you really only have 10 down clicks right now.  Is there a starting point on the ACOG that you can reset to and go by, instead of where it was set to last?  Also, if you didn't mount it in the exact same spot, it could change the click requirements by a bit more.  I am not familiar with the ACOGs range of adjustment.  I would say that as long as the reticle does not look to be in a weird place in the sight picture, and as long as you still have plenty of adjustment, it doesn't matter.  Or you can measure how far the rail is from the barrel at several points and see if it was mounted evenly.
4/23/2012 12:09:46 PM EDT
[#7]
I went 3 clicks in the opposite direction so the net change is 17 clicks.  
It is 4 clicks per inch at 100m for TA11C so it makes sense.
On top of that, I am not sure the previous zero was that good, I think it was off to begin with.

Troy Alpha, nice rail.
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