Scope Rails

[gilcarleton]

I am new to long range shooting and just setting up my rifle. I am putting a Weaver scope rail on my rifle and I have a choice of one with 0 MOA or 20 MOA. I have read that the 20 MOA will allow me more clicks on my scope for long range adjustment but I would like to hear a little input before I make a choice. Do most people use this kind of rail or the 0 degree rail? Thanks so much for your help.

 

[MGYSGT]

If you are hesitant to put a 20MOA rail on your rifle, have you considered the Burris rings with the plastic insert that allows 0, 5, 10 MOA of adjustment. Just make sure you have clearance for the scope bell if you go that way. I had a Leupold that would run out of vertical adjustment at 600yrds and a 10 MOA Burris ring got me back in the black without aiming above it.

 

[lawman29]

What model of weaver scope and what are the specifications on the range of elevation adjustment? what distances will you be shooting min to max? what caliber is your rifle?

 

[Turbulent Turtle]

The way I look at it, irrespective of the riflescope you buy and the range at which you shoot, you lose half the elevation range just mounting the scope on the rifle if you use a 0 degree ramp. If everything is perfect, and the actual mechanical zero of your scope corresponds perfectly with the bore of your rifle when it's mounted on the rifle, you will need something like 2 or 3 MOAs just to get to 100 yards. My scope needs to come up about 30 MOAs to zero at 1000 yards. I need about 13 to zero at 600, all from the 100 yard zero.

With a 20MOA ramp, your mechanical zero scope should be pointing 20MOA below the bore of your rifle and at 100 yards, you will be about 17 or 18 MOAs below the middle of the scope. As the distance increases you get closer to the middle of the scope where the lenses have their sweet spot. Lenses perform best near their middle, edges don't do near as well.

So, if you shoot mostly at 100 or 200 yards, it's best to have a 0 or at most a 10MOA ramp. If you shoot at longer distances, a 20MOA ramp or even a 30MOA ramp will do better for you.

The Burris Signature rings are a great way to setup a scope and if you measure the distance between the middle of the two rings, with a little trigonometry (arctangent is your friend here,) you can calculate the MOA displacement that you get using combinations of 0.0, +/-.005, +/-.010 inch and +/-.020 inch (not MOA) offsets. For instance you can use a +.020 offset on the bottom of the rear ring and a -0.020 offset on top and reverse that for the front ring and you will bet a total offset of .040 inch for that scope. If the distance between the middle of the two rings is exactly 4 inches, you would get .57 degrees of downslope, or 34.2 MOA.

Bottom line for anything beyond 2-300 yards as your habitual distance, a 20 MOA ramp is indicated.

Even at 100 yards, a 20 MOA ramp will not hurt you, but you will not be looking through the very best part of the lenses. Trade-offs, everywhere.

 

[snakepit]

+1 Denys, good synopsis of the topic.

 

[gilcarleton]

Just want to thank everyone for all of the advice. I was not sure if 20 moa would be too much at 1000 yd or if it would hurt me in short ranges. I should have mentioned the scope I bought. It is a Vortex Viper PST FFP 4X16. Since I already have the rings, I think I will order the 20 MOA rail. If it does not work, I will try something else. Thanks again.

 

[Turbulent Turtle]

I looked at the specs for that scope. It's a 30mm tube with 75 MOA of adjustment range. Essentially it's using internal lenses that are the same size as the ones used in a 1 inch tube, so you get the larger adjustment range.

This means you have about 37 MOA of up adjustment and using a 20MOA ramp will give you 57MOA. You should have no problems whatsoever with this setup.