Cinders Posted December 18, 2021 Report Share Posted December 18, 2021 While trying to track down a strange inaccuracy issue where I'd get a tight 3 round group in one spot and then a tight 2 round group 2 inches over to the right (rinse and repeat every grouping), I came across rub marks where the scope mount is rubbing, possibly the cause of the issue. The scope mount in the picture isn't where it was before, I had the scope mount 1 notch forward so it bridge onto the first notch of the shroud. After noticing the rubbing, I moved the mount back a notch to see if that fixed the problem (haven't been able to go shooting yet), but I can see the 2 points of contact again (2nd picture). Can I get some advice on this? Do I have the scope mount backwards? Should I file it down to fix the rub points? Am I doing something wrong here? Thanks! Quote Link to comment Share on other sites More sharing options...
unforgiven Posted December 19, 2021 Report Share Posted December 19, 2021 You pushed it forward and tighten to spec? Rubbing is usually caused by movement. Just my 2 mags Quote Link to comment Share on other sites More sharing options...
Cinders Posted December 19, 2021 Author Report Share Posted December 19, 2021 6 hours ago, unforgiven said: You pushed it forward and tighten to spec? Rubbing is usually caused by movement. Just my 2 mags Not sure what you mean on pushed forward. The front scope mount was on the first notch of the shroud rail and the 2nd mounting point was on the main body of the AR rail. I'm seeing that metal rubbing (sorry for blurry pic) on the shroud rail where the scope mount was touching it. I do suspect movement as well, but the question is why and what to do about it. Questions: 1) Should the shroud rail be moving like that to cause that rubbing? 2) Should the scope mount be touching the rail like that? 3) Moving the scope mount to be completely on the AR upper rail is a good solution? Or should I look at returning the mount or modifying it? Thanks for any advice? Quote Link to comment Share on other sites More sharing options...
shooterrex Posted December 19, 2021 Report Share Posted December 19, 2021 Always mount the scope mount on the receiver. Don't bridge onto the rail. Push the mount forward before tightening mounting bolts. That way it can't work forward under recoil. Your fore end was probably flexing under recoil and that is what caused the shiny spot. Quote Link to comment Share on other sites More sharing options...
unforgiven Posted December 20, 2021 Report Share Posted December 20, 2021 What he said 🍻🍻 Quote Link to comment Share on other sites More sharing options...
98Z5V Posted December 20, 2021 Report Share Posted December 20, 2021 Get an overall pic of the gun from the side. Need to get a general idea of where your eyepiece is in relation to the whole gun. Quote Link to comment Share on other sites More sharing options...
blue109 Posted December 20, 2021 Report Share Posted December 20, 2021 (edited) Generally speaking you shouldn't bridge the gap with the mount. You want a solid platform for your optic. Very few handguards have zero movement relative to the upper. Edited December 20, 2021 by blue109 Quote Link to comment Share on other sites More sharing options...
Windwalker Posted December 21, 2021 Report Share Posted December 21, 2021 What they said. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted December 22, 2021 Report Share Posted December 22, 2021 On 12/19/2021 at 8:16 PM, 98Z5V said: Get an overall pic of the gun from the side. Need to get a general idea of where your eyepiece is in relation to the whole gun. @Cinders, can you get this done? Post the pic of the overall gun. Quote Link to comment Share on other sites More sharing options...
392heminut Posted December 25, 2021 Report Share Posted December 25, 2021 On 12/21/2021 at 8:54 PM, 98Z5V said: @Cinders, can you get this done? Post the pic of the overall gun. I agree, we can't tell if you scope mount is backwards without being able to see the whole mount. Nice, sharp, up close pictures (which yours certainly are) are great at times but other times an overall pic can be more useful. Quote Link to comment Share on other sites More sharing options...
Cinders Posted December 27, 2021 Author Report Share Posted December 27, 2021 Sorry for the delay, been stuck on non-stop 24 hour shifts due to holidays and staffing (thanks corrupt politicians for ignoring major city problems!) Thanks for the replies thus far. I should be headed to the range this coming week to test if the rubbing was the issue. Attached is a distant photo. Note: I moved the scope mount back 1 lug, this is after I saw the rubbing. Originally, the front of the scope mount was on the first shroud lug (bridging the shroud and the upper). I emailed American Defense and got a lackluster reply that repeated what I had said the problem was. I asked them if I have the mount backwards or why does the scope mount have 2 weird points of contact. Response: "Thank you for contacting us. It looks like the rail may be shifting under recoil or the rail lugs are taller than normal and are rubbing on high spots on the rail." Quote Link to comment Share on other sites More sharing options...
Cinders Posted December 27, 2021 Author Report Share Posted December 27, 2021 (edited) On 12/21/2021 at 9:54 PM, 98Z5V said: @Cinders, can you get this done? Post the pic of the overall gun. Ok, I suck at quoting. Trying to quote 98Z to get your attention. See post previous to this one! Sorry for confusion. Edited December 27, 2021 by Cinders Quote Link to comment Share on other sites More sharing options...
blue109 Posted December 27, 2021 Report Share Posted December 27, 2021 @CindersShould be good to go. The levers are on the left side so the mount is oriented correct, but honestly it probably wouldn't make a difference since it's not a cantilevered mount. Just make sure it's torqued down on the rail. My ADM mounts are all set up so they take a fair bit of force to lock down and are somewhat of a pain to remove. I'd say go shoot it and see if it's fixed. I'd also say I have a tendency to make a similar 3/2 shot group and I'm pretty sure it's me but Ive seen people suggest the barrel is warming up on the last two. Also, instead of quoting, you can plug in someone's user name after the @ symbol to tag them. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted December 28, 2021 Report Share Posted December 28, 2021 7 hours ago, Cinders said: Scope position on the rifle is good - the scope eyepiece should be at the end of the upper receiver - and yours is. If it's not, if fuks up eye relief for "normal people." Scope position ON THE GUN is good. Here's an EASY solution. MOVE THE SCOPE MOUNT BACK, so it's not bridging the gap to the upper receiver rail. That will entail that you MOVE TO SCOPE FORWARD in the mount - and you have plenty of room to do that, from the pic. That will fix everything that's scope-mount related, in this whole issue. It's simple. Quote Link to comment Share on other sites More sharing options...
blue109 Posted December 28, 2021 Report Share Posted December 28, 2021 I'd get behind the gun and try it at max and min magnification before I moved the scope in the mount. Might be fine where it's at. Quote Link to comment Share on other sites More sharing options...
jtallen83 Posted December 28, 2021 Report Share Posted December 28, 2021 I have a mount of that style with a PA 4x16 I use for test firing and breaking in new rifles. Almost always have to adjust the levers to get the tension right for each rail, if it's easy to open the levers then it ain't tight enough, ADM's directions on that seemed a bit misleading to me. I usually end up with some wear marks right ahead of that front lever as well, can't say it's been an issue. Quote Link to comment Share on other sites More sharing options...
Cinders Posted December 29, 2021 Author Report Share Posted December 29, 2021 On 12/28/2021 at 8:19 AM, jtallen83 said: I have a mount of that style with a PA 4x16 I use for test firing and breaking in new rifles. Almost always have to adjust the levers to get the tension right for each rail, if it's easy to open the levers then it ain't tight enough, ADM's directions on that seemed a bit misleading to me. I usually end up with some wear marks right ahead of that front lever as well, can't say it's been an issue. I'm contemplating doing a single pass with a file across those 2 friction points on the scope mount. I can't see anything positive coming out of the 2 contact points. Plus it rubs down the metal Quote Link to comment Share on other sites More sharing options...
unforgiven Posted December 29, 2021 Report Share Posted December 29, 2021 Touch it up with a black marker Quote Link to comment Share on other sites More sharing options...
98Z5V Posted December 30, 2021 Report Share Posted December 30, 2021 7 hours ago, Cinders said: I'm contemplating doing a single pass with a file across those 2 friction points on the scope mount. I can't see anything positive coming out of the 2 contact points. Plus it rubs down the metal That'll work. Quote Link to comment Share on other sites More sharing options...
Cinders Posted January 12, 2022 Author Report Share Posted January 12, 2022 Solved! Thanks for the help and advice, everyone! I was getting a weird pattern before: firing at one point, I would get 2 distinct, tight groups split by several inches. After taking it apart, we figured that the barrel and comp were torqued correctly, the gas tube was correct and not rubbing, and the shroud was not rubbing either. The scope mount was very tight and torqued to specs. It appears to have been this rubbing issue with the scope touching the shroud railing. I moved it back a lug to be fully on the upper receiver and the problem seems to have gone away. Note: not a split group in picture, that was me dialing the scope in on 2 different groupings. Quote Link to comment Share on other sites More sharing options...
Belt Fed Posted January 12, 2022 Report Share Posted January 12, 2022 I'd say you got it, some nice groups. how far was you? Quote Link to comment Share on other sites More sharing options...
Armed Eye Doc Posted January 12, 2022 Report Share Posted January 12, 2022 Nice shooting! Thanks for coming back to give the resolution. Quote Link to comment Share on other sites More sharing options...
Cinders Posted January 12, 2022 Author Report Share Posted January 12, 2022 4 minutes ago, Belt Fed said: I'd say you got it, some nice groups. how far was you? Hundie Quote Link to comment Share on other sites More sharing options...
Belt Fed Posted January 12, 2022 Report Share Posted January 12, 2022 4 minutes ago, Cinders said: Hundie Really nice groups then. Quote Link to comment Share on other sites More sharing options...
98Z5V Posted January 12, 2022 Report Share Posted January 12, 2022 Fine work, man - you've done well. Quote Link to comment Share on other sites More sharing options...
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