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10/1/2004 8:12:48 AM EDT
We have a customer that stated that switching a zeroed upper over to another lower changes the zero/point of impact.  Obviously moving an upper from a  tuned target lower to a stock lower will have an effect on accuracy, but this is not what the issue is.

I was actually speechless for an answer and it seems very silly for me to have to ask for help on this subject, but from a business standpoint and trying to answer professionally without disrespecting or demeaning the individual, I do need some additional advise.

TIA
10/1/2004 8:37:29 AM EDT
[#1]
You are in a tough spot.  It's easy to take him to the range to prove it doesn't change the zero.

But you'll never convinve him by arguing or by pointing to research articles (too many like that on this board).  I'd advise you just ignore him if you can.
10/1/2004 9:11:54 AM EDT
[#2]
I would ask him what other variables there where.  Was the rifle originally sighted in lower/higher temps, is there an elevation/barometric change between the 2 days, was there a lot of wind that day, has the lot/type of ammunition changed, was he shooting off of a bipod/rest that caused barrel deflection, has he removed the optics or bumped the sights, can he swap back to the old one and the rifle shoot back to its original POI, and how much has he actually observed in POI shift?

IDHunt
10/1/2004 9:24:56 AM EDT
[#3]
Could he have a different stock lengths and therefore screwing with his sight picture?

10/1/2004 9:26:43 AM EDT
[#4]
If the stocks are different then the change in cheek weld will ruin the zero.
10/1/2004 11:31:06 AM EDT
[#5]
Is there a difference in sight distance? ie; 16" barrel and 20" barrel.
10/1/2004 11:38:08 AM EDT
[#6]

Quoted:
Is there a difference in sight distance? ie; 16" barrel and 20" barrel.



We're talking the same upper.  The only variable is the lower receiver.  
10/1/2004 12:26:55 PM EDT
[#7]
1. Have him send you the upper.

2. Rule out stupid problems like loose mounts.

3. Take digital video of you shooting groups with it with two or three different lowers.

4. If zero changes, figure out WTF is wrong, 'cause it seems  like a mysery.

5. If zero doesn't change, burn video onto a DVD/CDROM and send him back the upper and the DVD.

-z
10/1/2004 12:37:05 PM EDT
[#8]
I would like all the details on the two lowers.  Like the others said, the stock lengths could play a part in it.  I'd also want to know what triggers are in the two lowers; does one have a 2 stage or tuned trigger and the other a stock, OEM trigger?

You are in a tight spot here because I think this guy is smoking crack but you don't want to go around pissing customers off if there really is a problem.
10/1/2004 12:41:16 PM EDT
[#9]
Any difference in the trigger or stock length may reveal deficiency in the shooter, not in the upper or any upper/lower interaction.

What are physical effects the lower can make on the upper, while in battery?  

. upward force on the bolt carrier from the magazine / rounds in the magazine.
. making sure the operating spring has enough tension put the rifle fully into battery
.. any others?

-z
10/1/2004 12:44:20 PM EDT
[#10]
Parallax and cheek weld with different buttstocks?  I'm assuming it has an optic of some sort on it, it not then.....
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