I just got a ARMS 40A2 BUIS from Chris at Eagle_Firearms.

I shot a couple of test targets and am disappointed that the same plane aperature doesn't work that well.

I fired a 5 shot group with the large aperature with UMC 55 grain MC ammo.  The first group was 2.5 inches in diameter at 50 yards and was 2" low.
Group 2 I fired 5 shots with the small aperature was 2 inches in diameter but moved the group to the one o'clock position on the target and was 4.5 inches away from the first group at 50 yards.  

I repeated with my match ammo 69 Sierras.  Same sight settings.
Group 3 with small aperature was also at the 1 o'clock position.  Group 4 was fired with the large aperature and was at the 9 o'clock position on the target for a shift 3.6 inches at 50 yards.

Is this normal with ARMS sights?  I think it's pretty lame.  The sights will eventually be a backup to an aimpoint but still.  The shift is diagonal across the target when flipping the site.  

Suggestions? Comments?

Thanks,
Tom

i did not know they had a #40a2 in sp

You are correct sir!

I re researched and found myself to be in error regarding ARMS having a same plane aperature 40a2.  I sit corrected.  

I still have issue with the point of impact moving horizontally with my 69 gr. match loads.  Moved more horizontally than vertical.  Horizontal shift of 3.25 inches at 50 yards.

For further information I was shooting off a hoppes rest w/ rear sandbag and the groups for the match loads were 1.25 each at 50 yards.

Tom

Zero using the small aperture at 50 yards.

I don't know why you have such large POI  shifts.  Mine only changes by moving downward about 2 inches when switched from Small to Large, with no evidence of a windage shift.  I DO shoot NTCH.  

Unless you intend to engage distant targets using the Large aperture, I suggest you re-zero using the Small aperture, and then just "take what you get" at close range using the large hole.  COM hits will NOT be a problem at close range.

The 40A2 deploying initially with the LARGE aperture only makes sense from a CQB point of view.  My Zombie rifle does wear a 40A2.  As a civilian rifleman I prefer the 40L-SP which deploys using the Small precision aperture.  My "walking varminter" rifle (1/12 govt. profile) has a 40L-SP tucked underneath the 15X glass.  YMMV.

Paladin

Paladin,

Excellent point regarding zeroing with the long range aperature first.  I should know better.  Thanks for taking me back to school.  In the Marines we weren't supposed to use the large unless it was night.  I know CQB is not the KD range.  

What do I know, I was an M60 gunner, we didn't use the rear sight much at all!  Makes my heart sad to see the M60 getting replaced.  I always had good luck with it.

Thanks,
Tom