Bedded the rail - now I can't zero the *&^% thing...

ShootingNewbie

Regular
EE Expired
Rating - 97.7%
43   1   0
Location
Vancouver Island
Sooo... I'd been meaning to bed the scope-mounting rail on my 6BR for a while now. When I first installed the rail, there was a small bit of play between the rear of the action and the bottom of the rail, but when the screws were tightened to spec, it cleared up. Still, didn't like the fact that the rail was essentially being bent into shape by this; didn't have enough time to do things right, tho.

Finally, work slowed up a bit, giving me some free time, so grabbing some Devcon that I didn't have a use for, and after reading/viewing all the articles and videos on the subject I could find, I did the prep work and bedded the beast - let it cure for a week (overkill on the wait, but there's always stuff getting in the way of fun...) and took it out to the range.

I knew that I would have to re-zero after the disassembling/bedding/reassembling process, so at 100 yards, I aimed at the center of a target, and fired a round. No hole, but I did see a puff of dust from behind the target - it seemed high. Aimed the second shot at the bottom of the target, and I'm just barely on paper at the top of the target. "No problems - just need to adjust POI downwards", he thinks to himself.

Well - as you may have guessed by now, I can't move POI downwards far enough to get POI and POA to line up at 100 - I ran out of clicks with the POI about 4" higher than POA.

Salient technical details: Scope is a Sightron 10-50x60 SIII - their website says that it has 50 MOA of E-W adjustment (which I'd assume is the same in the vertical department). Rail is a Farrell 20 MOA, action is a Savage PTA, and rings are Burris Signature Zee's, with the plastic inserts).

Any ideas here? My thoughts, in increasing order of nastiness:
- Did I build up too much bedding under the rear of the rail (easy to remedy by re-bedding and going easier on the devcon);
- Is a 20MOA rail too much for 100 yard work (can replace with a 10 or 0 MOA rail);
- Did I bend the scope by mounting it in a slightly radiused rail for a year or so (Don't want to contemplate this option...)?

It just hit me that I might be able to get it closer to zero by using the eccentric inserts in the rings and setting the scope high in front and/or low in back to bring the POA up; I'm pretty sure the inserts in there currently are the non-eccentric ones. (If I'm doing the math correctly, a +10MOA corrective insert at the front should get me back on paper with 5 or 6 MOA to spare.)

Which leads me to one more question (for bonus marks) - if you're setting up your rifle with a 100 yard zero, where would you ideally want your zero setting falling in your elevation adjustment range? In the center of the elevation adjustment range (i.e. so that you can click 25MOA up and 25MOA down), to maximumize the available clicks for windage adjustment, or somewhat closer to the bottom of the elevation adjustment range, in order to give more flexibility for setting up for longer-distance shorts? Or do you care, just as long as it's zeroed?

Thanks for any thoughts you can pass along about the above.

ShooNew.
 
You will never need down elevation so ideally you should be zeroed at the bottom. That's why it's called elevation.
The 50 MOA E-W is Elevation and Windage.
The bedding compound should only be thick enough to fill in the imperfections not change the elevation.
 
The SIII's function throughout their travel range so you can set up the zero any where you want. Leaving the zero where you are is ideal for longer range shooting... many work hard to set up their scopes that you "lucked" into.

If you are only shooting at SR, you can use the shims in the inserts to remove the cant in the scope thus requiring more up to zero at 100yds. You can always change it later to whatever you want.

And that is the joy of the set up you have. Anything is possible. Just shim accordingly for whatever suits your tastes.

Jerry
 
The SIII's function throughout their travel range so you can set up the zero any where you want. Leaving the zero where you are is ideal for longer range shooting... many work hard to set up their scopes that you "lucked" into.

If you are only shooting at SR, you can use the shims in the inserts to remove the cant in the scope thus requiring more up to zero at 100yds. You can always change it later to whatever you want.

And that is the joy of the set up you have. Anything is possible. Just shim accordingly for whatever suits your tastes.

Jerry

I just checked the scope, and I can't really leave things as they are - with the scope bottomed-out (topped out???) elevation-wise as it currently is, the windage adjustments have about 5 clicks that they can move either left or right before hitting their limit, and the crosshairs seem to stick somewhat when moving back and forth.

I think that I'll be using the inserts to get the POA and POI to intersect at least 5 or 10 MOA away from the elevation extreme limit, as that seems to gives me about three-quarters of the full range of windage movement that is possible when the elevation adjustment is at the center of its range. I'd still have 40-45 MOA of elevation adjustment available for longer ranges, which should just get me out to 900-950 yards, according to iSnipe.

It seems like the range of possible windage/elevation adjustments is best described by a circle - you get the most left/right adjustment when the up/down is at its center, and the least when you're at the top or bottom of that circle.
 
You turned your 20moa rail into a 50 MOA rail with the use of epoxy...strip it off and try again. Tighten the front screw to 10 in lbs and the rear screw to 7 in lbs. Leave for 24 hours and try again.
 
You turned your 20moa rail into a 50 MOA rail with the use of epoxy...strip it off and try again. Tighten the front screw to 10 in lbs and the rear screw to 7 in lbs. Leave for 24 hours and try again.

This !

Quite frankly I've never seen the merit to bedding a rail. Use blue Loctite and torque to recommended Lbs and leave it be.
 
Something went wrong somewhere... and I like Marinetex specially because its easy to do nice thin skim bedding with it, flows just right and looks better than anything devcon in areas that can be seen.
I'd start over.
I never used those zee rings, maybe something going on with your inserts adding even more elevation? Are the rings sitting properly on the rail?

There's some value to doing a proper skim bedding on low quality factory actions, they're usually all over the place, and rails can have some inaccuracy as well.
I like to check mating surfaces with Prussian blue first and see what touches where.
 
Back
Top Bottom