thoughts on putting 1 scope ring on forearm=effecting accuracy

[LongArm]

I am about to build a lr308. I do not want to use a cheek riser or a extendable stock like the prs. I will be running a bushnell elite 3.5-21x50. The last time I looked at doing this I needed a forward extended one piece mount to stay on the reciever and keep from getting on the forearm Still needed a prs style stock to get more length). I would like to use either a magpul moe rifle stock or a ubr stock. I remember that I could not get good cheek weld with raised 1.4" one piece mounts. I would like to use regular rings that are not as tall. The rifle will be most likey a lr308 in 260 remington with a 24" barrel. I know the monolithic would prevent alot of these problems, however I am curios if it would matter putting a scope across the receiver to the hand guard.

So here are my questions;

1. Will putting the second scope ring on the forearm area (close to the receiver) of a mega mkm https://www.rainierarms.com/?page=shop/detail&product_id=3479 effect long range accuracy?

2. Is it possible to get a good prone cheek weld with using scope rings around 0.92"-1".

3. Will a a scope with a 34mm tube and 50mm objective clear the forearm with rings smaller than 1.3"

4. Has anyone actually done it or seen it tested for long range accuracy?

 

[BobinNC]

1. Yes, it can affect LR accuracy. Will it? I don't know as it depends on factors that are unique to your rifle. But I feel safe in saying it's generally a bad idea.
2. Depends on the rifle and your face shape/size. Generally that is too low for an AR-10, AR-15 type/style rifle.
3. You need a minimum of 1.16"+ without BC covers to clear on most 50mm objectives. They generally run about 2.32", you need to clear half of that. What's the OD of the objective end of the scope your putting on?
4. Not done it, nor seen it done. But it is NOT an urban legend. Forearms on AR rifles can and do move a little bit. And any movement is bad for accuracy and really bad for your scope...

 

[I Am Hero]

Only ever did it with a scout scope before. Didn't shoot it long enough to determine if it affected accuracy that much. I realized using my spare scout scope on an AR platform was stupid and bought a real scope before I could find out.

 

[tickled pink]

What height do you need for a good comfortable cheek weld? I have had a problem getting the correct one for me. I need 1.5 inches from the top of the Picatinny rail to the center of the scope tube. I ended up using a Warne Ultra High QD aluminum rings which are very light, but strong and have shorter ones in 30 mm rings also. I also have a Bushnell AR/223 scope with 4.5-18x40mm zoom which has tactical turrets which are accurate as my Vortex 6-24 PST FFP MOA scope.

You can see how it is set up in my picture. You can also see the end of the B-SQUARE bubble level just left of the rear scope mount which helps shooting long range.

OOPS now I see that your scope has a 34mm tube.

 

[morganlamprecht]

i have .92" rings in 34mm, 1.55" mount in 34mm, and an ERS you could try it out...off the head tho, i doubt the Obj bell will clear with rings that low...my swfa 5-20 (30mm tube, 50mm obj) is in a 1.47" 20moa mount it rides the rail pretty tight at the bell w/ a scope cover on it

 

[GH41]

I wouldn't bridge the gap with individual rings but I might with a solid base mount. Problem is I have never seen a receiver and hand guard rail that where the same exact width, height and precisely aligned. If you are building a new rifle as you say look at a monolithic upper and rail set. You can put the scope where you want.

 

[LongArm]

Probably easiest to go with the monolithic rail system. I think my badger mount is 1.49" high. My scope objective is 2.365" so figure half is 1.18". I'd need around 1.26" scope ring height. I just wanted the scope as low as possible.

 

[LongArm]

I bought a mega monolithic. I am also running 1.26" seekins rings. The rings give a good sight picture. I think to get a good sight picture without an elevated cheek piece you'd need around 1" high rings. I think that is why gap does the forearm the way that they do ( without the middle picatinny on the top.

 

[allghilliedup04]

i cant speak for a 50mm objective, but i have had my fround mount of my scope on my forend since i built my SPR with no ill effects on accuracy. I think its silly to use the typical AR mounts when building a longer range gun. sights closer to to bore i was always taught. i consistantly shoot my 556 out to 800 with a 1-4 power with no issues.

also we used to mount our S&B partially on the forearms on our Mk11's in the Marine corps too. Id say as long as you have a solid fore end i wouldnt worry about it.

 

[Raivkka]

I thought the problem with putting 1 ring on the receiver and 1 on the forearm was that the two different pieces move/flex when shot and put torque on the scope tube (risking damage to the scope).