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Blasphemy to drill/tap the receiver on a M12 for scope bases?

994 Views 34 Replies 12 Participants Last post by  gcrank1
I really like my H&R M12. I bought it without any sights. It came with the EGW scope base that bolts to the rear scope block mounting holes on the barrel and hangs out over the receiver.
I can feel the whole scope/mount vibrate a little when fired, and can see movement if I push down on the rear of the scope. However that is not really the main issue.
My main issue is the scope base does not extend back far enough to get a good eye relief.
I have the scope rings back as much as I can, and the scope as far back in the rings as I can, and it is still not comfortable. I have to move my head forward to get a proper picture through the scope, to the point it is not natural.
It is not LOP issue, as that fits me perfectly. The original stock that came on it when I bought it had been cut down to a shorter LOP and it was too short and uncomfortable. And I still had the eye relief issue with it.
While some do not like the stock, I find it actually very comfortable.

With the current scope mount not extending over the rear receiver ring, I got thinking, how much would it be frowned upon to have the receiver drilled/tapped for a scope base (either one or two piece) on top of the receiver?

It is a shame they do not still make the Ken Viani mount, and no one has started reproducing it. Finding one is very hard and cost almost what I paid for the gun if you do find one.

Or, does anyone know of any other scope bases/mounts for the M12 that can put the scope over the receiver?
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I hope I'm not telling you something you already know. The "zero moa" refers to external elevation for your scope and has nothing to do with barrel diameter. One moa equals just a tiny bit over 1" at 100 yds., so your poi (point of impact) would be ~10" higher at 100 yds. than with the 0 moa base, all other things equal.
No worries! The question is the EGW mount comes in three flavors: 0 MOA, 20 MOA, -20 MOA. The only guidance EGW gives is the -20 is needed if you have a barrel that tapers to 0.75" at the muzzle, so you end up with a net 0 due to the barrel taper. I assume that means 0 MOA is the correct one for the heavier barrel like I have. I just cannot find confirmation of that anywhere.
 

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No worries! The question is the EGW mount comes in three flavors: 0 MOA, 20 MOA, -20 MOA. The only guidance EGW gives is the -20 is needed if you have a barrel that tapers to 0.75" at the muzzle, so you end up with a net 0 due to the barrel taper. I assume that means 0 MOA is the correct one for the heavier barrel like I have. I just cannot find confirmation of that anywhere.
I'd be very curious to know why EGW says that. MOA means minute of angle, of course, and there's no relationship between moa and barrel taper. Does the EGW base mount on the barrel? If so, then maybe they're referring to the shape of the base at the mounting surface matching the taper of the barrel to avoid leaving a gap. Perhaps the 0 moa base is shaped differently at the bottom than the 20 and -20 bases. But if it goes on the receiver then it shouldn't matter. Maybe you should ask EGW.
 

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I'd be very curious to know why EGW says that. MOA means minute of angle, of course, and there's no relationship between moa and barrel taper. Does the EGW base mount on the barrel? If so, then maybe they're referring to the shape of the base at the mounting surface matching the taper of the barrel to avoid leaving a gap. Perhaps the 0 moa base is shaped differently at the bottom than the 20 and -20 bases. But if it goes on the receiver then it shouldn't matter. Maybe you should ask EGW.
Yes, the EGW mount uses the rear scope mount on the barrel and then cantilevers back over the action.
 

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Thus mounted on the barrel taper it must be accounted for from a true bull (constant) dia. barrel as it gives some 'extra elevation' based upon the angle created to the bore-line.
The scope, will 'point down', thus elevating the muzzle and shooting a higher trajectory (often needed for the now popular 'long range' shooting).
The -0- moa cantilever mounts duplicate what typical dual, or one piece scope bases do, IF mounted on a section of parallel to the bore barrel (often a tapered barrel will have a 'bull' dia. section just ahead of the receiver before the taper begins.
The +/- moa point the rail itself up or down so accommodate the range of the scope elev. adjustments for closer or farther away/special circumstances.
It is mathematical to great degree once you have defined your preferred distance and proven your point of impact.
 

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I'd like to know if the OP bought the SK Viani mount. We need a review on that.

Way back in the thread I talked about my brilliant idea of putting the set screw in at the rear of the EGW mount so that you could null out any kind of cantilever movement on the base. I used a little piece of milk jug plastic to act as a shim between the set screw and the receiver so I wouldn't mar the receiver with the screw. I really admired my brilliance at that piece of work.

Maybe I was a little bit ahead of myself on the brilliance thing. I had a chance to get the rifle out and work on tuner settings yesterday. Started off shooting two shot groups from 140 to 180 on the tuner (Harrel's) moving in 5 click increments. I had things adjusted so that I was in line with the horizontal axis of the row of bulls but a little off to the right so I didn't blow out the aiming point. Shot ten 2 shot groups and decided to zoom in on the 163 to 172 setting moving one click at a time but still doing two shot groups.

I use a one-piece rest so I dropped down a row on my tuning target and popped the first shot at 162. It hit about 1/4" low. All of the next groups were also low by about that same 1/4". This should not be. Since I had previously shot at 165 and 170 one row up and all was OK, I was a bit stumped as to what was happening.

Next culling was to do 5 shot groups from 168 to 172 on the next row down. Again, the shots were low but even lower now by almost 1/2" !

I picked 169 as the place to be and dropped down another row to do consecutive 5 shot groups at that setting. There is a bit of a story with me adding a 7 ounce weight to the tuner after which i had a series of very good groups but that isn't relevant at this point. But, about half way thru this string, I got tired of hitting low so I adjusted the scope to get things back on the bull. 3 more groups on this row and three more on the next row were all at the same POI with no downard drift. It appeared that the rifle had, miraculously, healed itself.

Came home and this morning started to clean the rifle. I picked it up and - KaBoom! - my brilliantly constructed piece of milk jug plastic fell right onto the floor.

So, the screw loosened up and the back end of the EGW base moved down. The front of the scope moved up and that pushed the POI down. I ordered set screws today that have the nylon tip. I'll use these and Loctite the set screw in and I should be home free from now on!

So the moral is to not feel so brilliant because when it's revealed that you're not....well.....you just feel kind of dumb.

Tony
 

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Discussion Starter · #27 ·
I did not order the S&K mount.
After inspecting the pictures they sent me, it will not move the scope back any further than my current EGW mount. It pretty much puts the rear most slot you could put a scope ring, at the same spot.
I asked if they had plans to, or would add slots all the way to the rear and they said the design would not allow it.

So for now I am just dealing with what I have while I contemplate other options including making my own mount.
 

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I did not order the S&K mount.
After inspecting the pictures they sent me, it will not move the scope back any further than my current EGW mount. It pretty much puts the rear most slot you could put a scope ring, at the same spot.
I asked if they had plans to, or would add slots all the way to the rear and they said the design would not allow it.

So for now I am just dealing with what I have while I contemplate other options including making my own mount.
Jeep,

Thanks for the update. I just put a Sightron 36X scope on mine and I was OK with where the scope wound up. i do have a ring right in that last slot.

Tony
 

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Discussion Starter · #29 ·
Yea my rear scope ring is in the last slot, and the center part of the scope that has the turrets is about 1/8 in away from that rear scope ring. So I have it back as far as it can go.
It is ok on low power, but when I zoom in, you naturally have to move a little closer to the scope for a proper picture, and that is where I have the problem.
 

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I did it and never looked back. Two piece steel picatinny bases. Be sure to specify picatinny bases as Weaver rings will fit pic, pic will not fit Weaver. Burris XTR Signature rings will give you the option of +/- 0, 5, 10, 15, 20, 25, 30 or 40 MOA. I used +30 to get standard velocity 22LR out to 300 yards. This way I can dial elevation from 25 to 300+ yards well within the adjustment range of my scope. I couldn't be happier with the set-up.

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Here is Daughter #2 getting comfortable behind the gun.

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I did it and never looked back. Two piece steel picatinny bases. Be sure to specify picatinny bases as Weaver rings will fit pic, pic will not fit Weaver. Burris XTR Signature rings will give you the option of +/- 0, 5, 10, 15, 20, 25, 30 or 40 MOA. I used +30 to get standard velocity 22LR out to 300 yards. This way I can dial elevation from 25 to 300+ yards well within the adjustment range of my scope. I couldn't be happier with the set-up.
Nice set up! How did you mount the bipod to the rail?
 

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Discussion Starter · #33 ·
I did it and never looked back. Two piece steel picatinny bases. Be sure to specify picatinny bases as Weaver rings will fit pic, pic will not fit Weaver. Burris XTR Signature rings will give you the option of +/- 0, 5, 10, 15, 20, 25, 30 or 40 MOA. I used +30 to get standard velocity 22LR out to 300 yards. This way I can dial elevation from 25 to 300+ yards well within the adjustment range of my scope. I couldn't be happier with the set-up.

View attachment 356472
Glad to see someone has done it.
I have not decided for 100% if I am going to drill/tap it yet or try and make my own mount.
 

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Took mine to the range recently which reminded me that massively oversize stock keeps me from being able to get a proper sight picture with the irons. I will probably be selling mine. The only way I could use it is to scope it. I got it the first year the CMP offered them.
 
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