20MOA mount?

[Mr Smith]

So My new mount came in (american defense recon S) and it verified my suspicion that after I lapped the rough spot out of my Primary Arms scope mount it should have been 0 MOA and make it easy for my scope to sight in. But nope. Still about 26MOA off in elevation if my math is right...(bullet would hit dirt well below the target if the scope elevation was at center of its adjustment range @ say 50yds)

So I have a 4-14x44 ACSS DMR 308 scope from Primary Arms for my DPMS gen 1 Low pattern .308 rifle.

The scope has 17.4mil adjustment range. (Roughly 60MOA total elevation adjustment)

put a bore sight in it and saw it is off by a LOT...like laser is at bottom of the scope with adjustment range in the center. So adjust till the laser is where it should be in the scope.. I verified where it should be via my 7.62x39 which is sighted in and dead nuts on, and the laser should be slightly low and to the left of center of reticle for dead zero according to the 7.62's scope with the bore sight in that rifle...

So adjusting this thing I am about 1 mil (turrets are in mils. 1/10th mil per click) from being out of adjustment range just to get on paper. My thinking is I will probably need a 20MOA mount to get most of my normal adjustment range back since I should have +/- 30MOA up and down and I only have about 3-4MOA left of adjustment and I'm not even zeroed yet...this is just to get close enough to get on paper. Leads me to believe either the scope is -20MOA or the upper receiver's pic rail is -20 MOA. But my thinking is a 20MOA mount should get me back in the close enough to center range to allow me to sight in at 100 and have some adjustment range back.

Anyone else have thoughts on this?

This is the mount I had in mind:
American Defense Manufacturing AD-RECON-S 20 MOA Scope Mount Up to $11.04 Off w/ Free S&H — 3 models

Y'all think it will fix the issue I'm having?

rifle in question:

BTW it has the 0 MOA american defense mount on it now (PA mount shown in picture above)

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[Mr Smith]

So I tested with a cheap junk walmart scope that is mounted in a burris pepr mount just sitting on my shelf. same issue.. have to adjust elevation nearly to the end of adjustment to get the dot in the crosshairs. seems that confirms the pic rail on my upper receiver is out of spec.

 

[Bealzybub]

What brand is the upper? Both Aero Precision and LaRue make a 20 MOA upper.

 

[Mr Smith]

What brand is the upper? Both Aero Precision and LaRue make a 20 MOA upper.

5D tactical .308 stripped upper, BCA 18" straight fluted 416R .308 barrel. "B308MSC18110(SSF)" and VG6 Gamma 7.62 brake

 

[Bealzybub]

Personally I'd get something (scope) that has a little more MOA you could dial in and run with it. I have several 20 MOA rails on my bolt guns.

 

[Bealzybub]

Oh and the aforementioned Burris Z ring sets.

 

[Mr Smith]

Personally I'd get something (scope) that has a little more MOA you could dial in and run with it. I have several 20 MOA rails on my bolt guns.

Rather stick with the same scope since the scope is not the issue, however sounds like you're also saying the 20MOA mount would likely fix the issue as it should point the scope downwards by 20MOA which is the direction I need it to go thus giving me back 20MOA worth of adjustment if I understand how the 20MOA mounts work correctly??

I just want to verify I'm not going to be wasting money throwing another part at it if it wont fix the issue I'm seeing.

 

[Bealzybub]

20 MOA mounts are designed for long range and so I dont know how or if it would work mounted backwards. If thats something you want to do, correct it with a mount or rings I'd go with Burris Zee and the inserts. I believe you can put in either or 5, 10, 15, 20. Make sure the set you buy comes with all the inserts. Actually, I bought a used set of them spendy bastids because I had a right left issue. There were no inserts with them but I called Burris and they sent me a full set free of charge. Good folks there at Burris.

 

[Mr Smith]

it wouldn't be mounted backwards... the rail on my upper seems to point my scope upwards towards the sky (as an extreme example) causing my bullet to hit the ground feet below the target at close range. (50yds)

From what I understand of a 20MOA mount is that it points the scope downwards allowing you to raise the barrel higher so you can lob the bullet out at further ranges...but in this case I need it to do that same thing in order for 100-200yds to be on target within a standard scopes average center of adjustment range.

 

[JustSomeGuy]

Personally, I'd call the manufacturer and make arrangements to get that upper replaced. You shouldn't have to muck around with buying and adding parts to make it function as intended.

 

[No_Regerts]

Personally, I'd call the manufacturer and make arrangements to get that upper replaced. You shouldn't have to muck around with buying and adding parts to make it function as intended.

This. Something isn't square. Do you have a set of rings you can throw on there for giggles to see if the same problem exists? You shouldn't have to buy a 20 MOA mount just to zero it.

 

[74bronco]

it may be a photographic illusion, but its still a possibility not mentioned yet, to me the barrell looks like it exits the end of the ff foregrip/hardguard low/below centerline suggesting maybe the barrel is not mounted truly square to the receiver and actually pointing down some, but to answer your question yes a 20 moa mount would effectively give you back 20 moa of vertical up adjustment in the scope.

 

[Bealzybub]

Personally, I'd call the manufacturer and make arrangements to get that upper replaced. You shouldn't have to muck around with buying and adding parts to make it function as intended.

Yeah that.

 

[Mr Smith]

it may be a photographic illusion, but its still a possibility not mentioned yet, to me the barrell looks like it exits the end of the ff foregrip/hardguard low/below centerline suggesting maybe the barrel is not mounted truly square to the receiver and actually pointing down some, but to answer your question yes a 20 moa mount would effectively give you back 20 moa of vertical up adjustment in the scope.

It's just the way that hand guard looks in the camera. It's sort of a triangular shaped hand guard. Wider at the bottom narrower at the top, but the barrel is centered in the hand guard, flush with the receiver, and torqued down.

 

[Mr Smith]

This. Something isn't square. Do you have a set of rings you can throw on there for giggles to see if the same problem exists? You shouldn't have to buy a 20 MOA mount just to zero it.

Tried 2 different scopes and 3 different mounts, including my newest american defense recon s mount that has free floating rings (never needs lapped) It's definitely that billet upper receiver from what I can tell.

 

[erslll]

What distance are you sighting in with the laser bore sighter?

 

[Mr Smith]

Furthest distance I can get inside the house. About 16-17yds. again compared it to the 7.62x39 which is already sighted in for 50/200yds on the chevron, and found where the laser shows in that scope on that rifle, and compared to where it's showing on the .308 with 2 different scopes.

Had it out at the range before the extractor broke on me trying to sight it in on paper and could never get it on paper or figure out where it was hitting because it was hitting so low you couldn't see it through the scope. after replacing the extractor I got a bore sight and wanted to see how far off it was and it made it plain as day why I couldn't get it on paper...was all the way at the very bottom of the scopes field of view.

And due to weather I won't be able to get to the range due to heavy snow between here and there.

 

[erslll]

Did you figure this out? ADM mount fix your problem?

 

[Stomper]

I have been going over unimounts for the last several weeks for my .308 Tikka, and decided on a Badger Ordinanace kit. Looking at the photos in the OP, it seems to me that although the mount looks "cool", there doesn't seem to be a lot of mounting contact to the rails, and the forward arm and scope ring seem like they would be subject to flexing/deformation as well.


The below drawings are of the kit that I chose, and illustrate what appears (to me anyway) a more robust design... just a thought.