20MOA Base/100m Zeroing Issues

B

Buzzard

Regular
Rating - 100%
69   0   0
Location
Chetwynd
Just looking for some advice here:

I have a Savage 308 long action mounted with a 20moa Ken Farrel base, Burris XTR rings, and a Falcon Menace 4.5-18x56mm scope.

Falsely I had assumed this system would work well together, during my attempt to zero after assembly I found out that I run out of adjustment when trying to zero at 100. The turret is right to the stop and my point of impact is still ~9cm high at 100m. Has anyone else had a similar experience, or the opposite experience with the same setup? I was hoping to gain the ability to play in the longer ranges, but really didnt want to give up the ability to zero at 100m and have that flexiblity. Trying to figure out if there is something painfully obvious I am missing, a problem with my scope, or a flaw in my setup. Thanks.
 
I have the same rings on a 20MOA base with a 5.5x20 Falcon and I have not had that problem on my Remington action. You should have enough elevation adjustment to get a 100 yard zero. If I were you I would try checking the following

1) are the rings both the same height (possibly one is out of spec)
2) is the 20MOA base put on backwards (20 MOA the wrong way)

if not those simple checks

3) try mounting with a 0 MOA base (maybe borrow one) and see if you can get a 100 yard zero
4) try mounting with a 10 or 15MOA base if you can find those

just my 2 cents
 
If, after trying Bolivar's first couple of sugestions, your still in trouble, cut a few shims from an aluminum beverage can, and place one under the front of the mount, shoot it and see where you are. (the reason you cut a few shims, is now you are at the range, and if one shim wasn't enough, you've got others)
 
I checked my setup this morning. I have 42 clicks to bottom from my 100 yard zero or roughly 14 MOA. I would not expect your rig to be anywhere close to bottom.

A couple of other thoughts

5) Check to make sure the base is sitting tight to the receiver and that there is not any junk wedged under it, especially in the rear.

6) Once it is off measure the thickness of the base at the screw holes front and back and take the difference in inches divided by the distance between the measuring points. 20 MOA is roughly 20 inches in 3600 inches (100 yards) or 0.0056 inches per inch. The base should have this same ration of elevation change along it's length. If not, the base may be flawed and giving you more than 20 MOA.

Regardless, Splatter's idea is a work around that should get things back to a 100 yard zero. Brass shim stock would be better but aluminum should work too.
 
Get a zero moa base. Your scope setting is exactly want I have ran for fours years, but I never shoot closer than 300 so my bottom is perfect for 300.
 
It doesn't take much to alter the point of impact if the base isn't seated as it should. About one thou .001" changes the impact by 1 MOA on a 6" base.
 
Ok well see there have been lots of comments. I will have to take to measuring the rings and rail to see if there is something out of spec. There is nothing under the rail, I installed it and it was spotless. It mounted flush as I checked for any need to bed prior to installing. It cant be installed backwards as the rear is rounded, front is flat. Everything was torqued to spec according to the pattern, so I really have a tough time imagining that any error there would be enough to produce the results I am seeing.
 
What you are experiencing is common. There is no way to know what your scope will see until you mount it and shoot it.

The same components on another rifle can/will give completely different results.

Since the goal is LR shooting, why not take advantage of your situation. Your scope should have marks on the upper part of the reticle. Just adjust your 100yds zero so some upper mark hits dead on - really doesn't matter which mark. That is afterall why there are marks in the upper part of any tactical reticle.

Now your reticle center will land some place further down range and you have the full scope elevation and bottom part of the reticle to plink much further out.

Once you start shooting beyond 500yds, you will be very glad you have ALL that extra up.

The goofiest zero I have had was 48" UP at 100yds. This dropped my 22 cal bullet around 1400yds allowing me to use my scope and reticle to push out to a mile.

having a slightly high 100yds zero is very easy to compensate for. Not having enough up to reach your distance goals is much more problematic to solve.

I have a few articles on setting up a scope for LR shooting on my website in the tech section.

Enjoy...

Jerry
 
Listen to jerry, it just makes sense. Less hassle and greater advantage for extended distances.
I understand thefrustration, when you want something a certainway , but some times it can be a blessing in disguise!
When you shoot out at 1000,your scope may be closer to optical center. Check it out with your trajectory tables and the range of your scopes elevation adjustment.

In the end, do what makes you most comfortable withyour setup.
Have fun, and straight shoot'in!
 
I have a FM 4.5-14 mounted in conventional rings on conventional bases. Zeros nicely from 100m to 900m, with no need for an inclined base. I much prefer to use the center aiming point in the scope. If I were to have to use different points at different ranges, the chance of using the wrong one under the stress of competition is too great.
 
Jerry and tiriaq both have good points. I guess it depends on how well you can remember things under pressure, and what distances you are shooting at.

Buzzard, perhaps you could consider the burris sig zee rings, as the different plastic inserts give a lot of flexibility. For instance, with a 20 MOA base (and using the 30 mm rings), you have the option of having anywhere from 0 to 40 MOA of cant (in 10 MOA increments).
 
You must log in or register to reply here.
Back
Top Bottom