I was curious about the repeatability of the optics mounted on the dust cover of the Galil ACE 556 NATO rifle when it's removed for cleaning and replaced, so I decided to shoot some groups after removing and replacing the dust cover. Targets were shot at a known distance 200 yard range, optic used is a TA44 1.5x mounted in the dust cover, wind was light and steady.

Starting group (UL corner) was shot, and then the dust cover was removed and replaced, next group (UR) of 10 rounds shot, then third (LL), and fourth (LR)...



Running the groups through OnTarget I get these results, all numbers are in MOA:



Offsets are from the POA (center of the target), same POA was held for all groups and there were no adjustments to the scope. Spread is the max distance from CTC of the outermost holes, also in MOA.

Doing the math, the average difference in POI (POI shift) caused by removing the top cover and replacing it is 0.5MOA. Average group size is 3.3MOA.

I am planning on mounting an Aimpoint on the rail on the gas tube and repeating the test to check if that location is steadier/more repeatable for optics.

AJ

interesting!  I figured there would be a slight shift.

Not too shabby.

How are you liking the 556 ACE? Any issues? I just got out of 5.45 and have been looking hard at the 556 ACE.

It's fricken awesome! The Galil was always one of those guns I thought was totally cool when I was a no money having kid. By the time I had money they were $3k and up for guns that had seen more action than a $5 hooker during fleet week. I was anticipating the release of the 556 ACE and jumped the week that they hit the distributors.  

I think the ergonomics on the new Galil's are just about perfect, plus it fits me and balances well. I was having intermittent FTEj, but I think I've traced that back to one magazine. I'll post details of that later.

AJ

Part II:
I moved an Aimpoint Micro onto the gas tube section of rail and shot groups for dispersion and shift. Between each group I removed the gas tube and replaced it to see how much the POI changed between groups.

The four groups to the left are 55gr GECO with everything the same except for messing with the gas tube. The top right group was shot with IWI 77gr OTM, the lower right group is from ZQI SS109.



The results.


I was really tempted to toss out that one high right shot in group #1, because it looks out of place. Removing that shot would have given a group size of 1.7MOA. I decided to leave it in because I believe that, based on the other groups that I've shot, that this really is a ~3.2MOA rifle. Wanting this Galil to be a 2MOA rifle just isn't justified by my results, no matter how much I want to be so.

The 77gr OTMs have a offset of 1.2MOA and a spread of 4.2MOA.

The ZQI SS109 have a offset of 2.8MOA and a spread of 5.5MOA.

AJ

Interesting results, both my 556 & X39 Aces didn’t have any noticeable POI shift from removing the top cover but that was with RDS at 50yds. Also both of my galil shot around 3 moa until around 200-300rds then the groups tightened up to 2moa or better. All my optics have been mounted just behind the separation on the rear rail.

0.5MOA would be around 1/4" at 50 yards, I'm pretty sure I wouldn't notice that level of shift.

I am not saying all ACEs have a 0.5MOA shift after pulling the dust cover, this is a sample size of 1 with limited data.

AJ

I’m sure it probably there, the fact that it’s as minimal as it is kind if surprised me.

even on the original design, POI shift wasn't much of an issue with new rifles.   its when they have a lot more use, esp. in military service that it becomes an issue.  if you ever had a Golani, you can see where they wear and slop creeps in...

With the new design (grub screw to tension the top cover) you could compensate for wear if it happens.

AJ