Sharing scopes between bolt rifle and AR?

AR/M4 AR Technical Discussion
1

What’s the best way to share a midrange scope (2.5-10 x 32) between an AR and a bolt action .223 rifle (Rem 700)?

On bolt action rifles the scope base is typically tilted 20 moa. I assume there is no tilt on a flat top AR upper receiver rail (or is there?).

When I transfer the scope from Rem 700 to AR, how do I get the 20 moa tilt on the AR?

2

What do you need 20 MOA base for? Usually they are used to reach extremely long ranges for scopes that lack enough adjustments in elevation.
Here is how I would do it:

  1. Get a 0 MOA, picattiny base for the bolt rifle.
  2. Install the scope in a quick detach, zero retaining mount such as ADM or Larue.
  3. Zero the scope on the bolt rifle. Once zeroing is done, I would put a witness mark on the scope mount/ rifle base so you know where to mount it.
  4. Put the scope on the AR.
  5. Zero the scope for the AR, while keeping precise track of adjustments.
  6. Once the zero is complete, write down the number of elevation/windage clicks you had to move from your bolt zero.
    Also, put another witness mark, perhaps in different color on the base/scope mount of the AR.
    The End.
3

Andy-

Any suggestions on specific mounts to deal with the height differences needed for a bolt gun and an AR?

4

Good point. I didn’t consider that. I would get the mount that would hold the scope as low as possible on an AR and then I would get a stock pack(Eagle, BHI, etc…) / adjustable cheek rest for the bolt rifle.

5

I was hoping you were going to get an answer, since I’ve been looking at the same issue. I have a 18inch AR rifle I’m using as my LR/Precision rig so I mounted a 3-15 Premier in a Larue LT104(?) mount. I think it may even be a tad high on a AR with that mount ( I have a PRS stock to deal with it) so on a bolt gun it would be really high.

I’m thinking that you’d need a base on the bolt gun with a really low one piece mount on top of that holding the scope. Then for the AR have a riser to put the one piece mount on, which I’ve seen some around.

Wish I knew the right combo of mounts and risers, if ti possible at all.

Sniper Hide forum might have more info, or someone with an answer since they deal more with higher mag scopes and bolt guns.

Eventually the 3-15 will live on a bolt gun, so then I’ll just go with standard rings and go with a more standard SPR type optic (2-10 or so) on my SPR. I just want my 3-15 to do double duty for awhile.

6

The Larue LT104 mount looks like it’s normal height for an AR flattop, but too high for a bolt action. From what I’m reading, it seems like AR rings/mounts should be about 1.5" in height while bolt action mounts should be much less, about .875".

I just noticed Larue sells a “Tactial Picatinny Riser QD LT-101” which raises any Picatinny mounted scope by 5/8". If you use .875" tapered rings on the bolt action rifle this riser should be just right to give you the correct 1.5" height on an AR flattop.

7

One choice is the Lt-101 riser ( 5/8 ) , another is the Smith Enterprise if you want a steel one on your AR that is 1/2". Lots of companies make risers as well

On your bolt gun just use any decent 0MOA ( non tapered one piece base ). First , I doubt you really need a sloped base for your 223. The NSXs have far more adjustment than most other scopes ( you will have a 50MOA “up” from mechanical center )

Secondly, if you use a sloped base you will have to make serious adjustments between the two rifles

I use a LT-101 on one of my ARs where the scope also goes on a bolt gun and it needs surprisingly little adjustment

8

I would get the mount that would hold the scope as low as possible on an AR

That can easily get you in a situation of not being able to get a proper cheekweld due to the straight line stock design of the AR. As said above, risers or riser block to stay on the AR and hope the cheekweld and eye relief work out on the bolt gun.

Keith