X-Shim Re-Test: Rock River Arms AR-15 Accuracy with FMJ and BTHP Ammunition

X-Shim Re-Test: Rock River Arms AR-15 Accuracy with FMJ and BTHP Ammunition


in my last video I tested the X-Shim
which is a product that takes up the gap between the upper and lower receivers on
an ar-15 getting rid of that rattle and wobble that you get especially as a
rifle ages mostly I wanted to see if the X-Shim would help increase the precision
of the rifle and I immediately got some questions about the statistical
significance of what I’d done since I only did four or five round groups there
were two with the shims two without and they were using 55 grain hollow-point
flat based bullets so what I’ve done is I’ve gone ahead and I’ve hit some more
targets using different kinds of ammo and we’re gonna take a look at those
groups but before we get going make sure that you subscribe to the social
regressive and you can like us on Facebook to get in contact with us and
talk about weird stuff show off your rigs there’s some pretty fun stuff going
on over there but here we go here are our groups first off we have this is my
75 grain boat tail hollow point these are from Hornady and my upper groups the
first groups that I did are with the x-gen last time I kind of flip-flop that
so these are with the shims and then these are without so you can see that
with these the groups did open up so up here we’re coming in at about one point
one eight three and then without the X Jim this is one point four three one
next up we have silver bear ammunition and this is steel case stuff from Russia
it has a zinc washed case so it kind of has a silvery look to it I’m using
62-grain hollow-point bullets in this these are by Metal Jacket bullets and
I’m used to these not grouping particularly well and you can see that
this first one with the X Jim is four point zero seven zero inches over four
inches and it actually went here and struck the other target just because the
the groups were getting that big this is not a wind flier there really was no
wind out of the range which is really weird for the range that I’m at and not
have wind going on there might have been maybe three miles an hour at best you
know just the sort of thing you can barely feel it on the back your neck
and yeah this is all just the rifle the ammo this is just how things went
and then here without the exome things reduced down to nearly three inches this
is 2.9 for two both of these are horrible and I wouldn’t attach too much
significance this might be an indication that the X gems don’t do all that much
but considering this is Steelcase stuff I don’t know I kind of discounted the
Steelcase stuff is pretty ugly next up we have Hornady 55 grain Full Metal
Jacket boattail and these are some custom loads as well for me and these are with
the X gem this came in at one a bit over one and a half inches 1.58 two inches
and then down here without the X gem one point six one three so just a again a
bit over one and a half inches it’s not all that much larger than this other the
stringing went more horizontal than vertical so I’d say it’s up to you to
decide whether or not this the X gem actually does increase the precision of
the rifle you can you know look at my groups here if you want you can try them
for yourself you can see what happens at the very least it does improve the feel
of the rifle it makes it feel like it’s new again to me it’s like when I work on
my car and a part is blown out and I get everything all tuned up fixed up again
it feels like I have a new car again and that’s sort of the same feeling again it
feels like a new gun you

11 comments / Add your comment below

  1. I watched this and the other xshim vid but didn't notice you addressing whether the shims impacted the gap (positively or negatively) between the receivers? My home defence carbine is not a target rifle (no free float handguard) so the accuracy isn't as much of a concern to me as much as potentially eliminating some dust/debris ingress could be. Eliminating the play between the receivers would be nice too but just curious if the would benefit me more than the rubber boot route.

  2. I think the data is showing the shims are a marginal improvement. And when you think about ratio of price of upgrades to increased accuracy. It actually is pretty decent

  3. Interesting. Have you tried an accu-wedge yet? It does the same thing, although I've never seen the x-shims so I cant comment on whether it accomplishes the goal in the same manner. Also, some receivers have set screws that can be used to take up the slack as well. Those have been more than I've wanted to spend. I'd be really interested seeing a video that compared the Accu-wedge to the X-Shims. I'd do it myself, but my shooting/youtube co-host has been off gallivanting through the woods trying to shoot Bambi (this time of the year hes impossible to get a hold of) and I've had an all consuming project for my apprenticeship (I'm 170 hours in and 120 of which were put in under 2 weeks while working full time). lol I've got videos out the ass on the back burner due to no free time. I'd say you could have my accu-wedge to test, but I'd have to find it and it would cost more to ship the damn thing than the wedge actually cost. lol If I remember correctly it cost like $2 or something like that. Also it would be pretty interesting to see an extended test of these devices. Skip the cheap crap ammo and stick to the nice stuff. More groups will give us more data to draw conclusions. We might see that in an extended test 20+ groups (10 with and 10 without) that it does make a marginal difference on average. We might see that over all there is no significant advantage. It would help us also rule out your shooting, not that I think you shoot bad. We'd see patterns, that's all, and I think the patterns would tell us a pretty good story of what is going on. Hit me up on FB… I've got an interesting idea that I'd like your opinion on.

  4. Cut sections of bungy strap to fill gap under back pin then feeler gauge gap at front pin cut flat shim stock to fill gap plus .001 to make it tite but REMEBER each time you open and close hinge loosens some some keep a good high round count between cleanings

Leave a Reply

Your email address will not be published. Required fields are marked *