I posted in this forum because I'm guessing this is where the most people who shoot slung up are.

I'm considering turning an optical match rifle into a service rifle under the new rules. While weighing the rifle, it fell over onto a concrete floor. The impact knocked the free-float tube (Midwest Industries SS) off-center about 1/2". To remove the tube, I had to put a dowel on the rail and beat the dowel with a hammer. This involved a good bit of force. The barrel nut did not appear to move or loosen during this process. The tube's threads appeared to survive intact.

Because everything looked OK, I reinstalled the tube. The barrel has always been slightly off-center in the tube. The tube re-installed OK, but the barrel looks a little more off-center than it was.

With factory ammo, this rifle runs about 1 moa off a bipod or bags. On first firing after re-installing the tube, POI had shifted right about 5" at 200 yards. Elevation was dead on. Group size was about what I would expect, maybe a little (.1-.2 moa) bigger. The scope's adjustments appear to be working just as well as they did prior to the drop. I have not run a box drill on the scope. Off bags and a bi-pod, nothing appeared weird. The only cause for concern was maybe a little bigger than usual groups size, but this could be due to the ammo I was using (American Eagle 50 grain varmint tip, Black Hills 75 grain re-manufactured match, and Hornady 75 grain match).

Next, I slung up and shot prone. The POI of impact shifted low and right. Center to center of the group, the shift would be about 5" at 200 yards. That range trip ended there.

I went back to the range today. Similar results were obtained off the bi-pod as before. I observed similar or bigger shifts in POI when switching to prone. My prone groups were running 3-4 moa. I don't have any data on my prone shooting with a sling group size, but I did not expect it to open up this much. I'm not very experienced shooting prove with a sling, though.

The thing that concerns me most is the shift in POI when switching from the bi-pod or bags to slung-up prone. With a free-float tube, I would not expect any shift. However, I do not have data on this rifle from prior to the fall for switching between bi-pod or bags and prone. I also saw signs that caused me to suspect the POI shift was not consistent from group to group.

My gut tells me to take the barrel off and re-install it. I'm suspecting the barrel nut is damaged or loosened in such a way that the barrel shifts slightly under sling pressure. Of course, my prone shooting could just be worse than I think too, and my suspected POI shift is just bad shooting.

I would appreciate any thoughts, suggestions, or feedback. Also, if I pull the barrel, should I go ahead and buy a new barrel nut? They cost $25.

Is your Natural Point of Aim good? How does the reticle behave when dryfiring?



I'd go ahead and do a box drill.

Yes, you should completely check out the gun and get everything right. Next is your prone shooting. Do not expect the same point of aim from shooting with a sling and shooting off a bipod. Two different things. What makes for small groups is having a solid and repeatable position. All your zeros should be from position not on the bench or from a bipod. Find a good low position and get your elbow under the rifle and don't move that elbow. Work on that for now.