bedding bowed Nightforce 1-piece 20MOA scope base on Savage Model 11...

[coyotemike]

i am compelled to share my experience regarding my recent mounting of a 1-piece Nightforce scope mount rail base on my model 11. I joined this forum for this purpose expressly, as I am not a member of any of the many rifle or shooting forums out there, and this seemed like a likely place, given the rifle in this discussion. I feel I need to reciprocate for the many invaluable posts I've perused on this subject and many more, and my experience here seems to be a bit unique.

Some background - I traded a Weatherby Mark V Accumark 300 Weatherby Mag for a couple of Savages a while back. Hadn't shot the gun in years - too painful - and I was looking for something versatile and accurate enough to hit coyotes from 350 yards or more, work for deer, and with a recoil that would enable some long range target work. And I always thought the gun 'threw' the first round out of a cold barrel (Krieger) anyway....

The model 11 Hunter in 260 Rem is incredibly accurate - after I found some accurate ammo - Fed Premium w/Nosler 120 gr BTs. Wow. Don't know if I can do better with constructed loads in this gun. Didn't like Remington CoreLok so much.... The other savage is the thumb-hole 17HMR...

Anyway, I swapped out the Nikon scope it came with (put it on the 17 HMR) for a 20 year old Swarovski 4-16X50 scope I took of the Weatherby. Used Burris Z-rings at first, on the stock bases. After shooting a bit, and getting wowed by its accuracy with factory loads (mentioned above), I thought I'd see how far it would range to, with that scope setup. Well, I had less than 13 MOA remaining in elevation (zeroed at 250), and windage was not in the center of turret travel, either.

So, I opted for a set of Burris Signature rings, which have a purported 10 MOA of adjustability with the eccentric bushings - a very clever design. After mounting the scope and sighting it in, I found I used about half the eccentricity just getting the windage in the center of travel, and serendipitiously, arrived at the center of elevation travel as well. The old scope has about 80 MOA total elevation and about 30 MOA windage - I never knew that until this exercise.

Well, while 35-40 MOA of elevation (above) is probably all I really will ever use, I thought with that much to work with, I might as well put a 20 MOA scope base on it, and see what the possibilities might be. So, I chose the Nightforce 1-piece Piccany base with 20 MOA, for the Savage SA.

Thanks for waiting - here comes the bedding part.

First, when I took the stock bases off, I found the front one was loose. I mean loose. Rub marks obvious, screws not backed out, but not even finger tight. I had experienced about 1 MOA of 'drift' in elevation at 375 yards over about 30 rounds and thought it was the ammo. Obviously, it was the scope base coming loose. Lesson learned - don't expect factory installs to be up to standard.

OK - the bedding. First, I proofed the base on the gun, and found that when either the front or the rear of it was down, the other end was about 8-10 thou off the gun. At first I thought this was an issue with the receiver top, but then when sighting down the base (off the gun) I could see it was bowed! Checked it on my welding true-block, and sure enough, it was bowed.

It took very little force - I estimate about 5-8 pounds - to push either end of it down, so when I screwed both ends down to the gun and eyeballed for true, it was straight! So, obviously this gun was straight on top, and the base was true on the bottom, but the casting of the base (I think it's cast, even though it's steel) bows it slightly. Don't know if other have seen this, as I have not seen this mentioned on any forum post anywhere, but my base was.

I still wanted to bed it, to get complete and uniform contact on all mating surfaces, so I used the KiWi shoe polish release on the gun and JB Weld, and tightened all screws down to set. It I had not tightened all the screws and let either end 'float' as is the typical recommendation found in the forums, I would have had a permanently bowed base. Probably not an issue with the Burris Signature mounts, but would be with a traditional fixed mount. Used the Q-Tip with WD-40 trick to clean up, as many posts suggest.

Oh, by the way, I did a test bond with a high-tech spray lube with Teflon to compare with the shoe wax - don't do that! The epoxy bonded right through the lube, but the shoe wax was a clean separation.

So, in conclusion, you came this far for the following:
- factory mounted optics should be completely torn down and done 'right'
- Savage round top receivers are probably not perfectly aligned with rifle bore - mine was off quite a bit in elevation and windage - but floating bolt head takes the worry out of that
- 1-piece bases may not be straight - my Nightforce wasn't - so don't assume any 'gaps' are due to the receiver top
- do use the shoe wax (or some similar wax) as a release, and don't assume any petroleum-based slippery stuff might work without a test
- you probably already know this if you shoot over 250 yards, but factory ammo accuracy varies widely
- the model 11 260 Rem is sweet!

[chukarmandoo]

My last base I installed I permanently epoxied the base to the receiver never to be separated again. I should of had it welded on.

[earl39]

Savage round top receivers are probably not perfectly aligned with rifle bore - mine was off quite a bit in elevation and windage - but floating bolt head takes the worry out of that

Want to explain how this works?

[sparky123321]

I was just about to ask the same question.

[coyotemike]

Earl39, your right, it doesn't. Wrong assumption regarding bolt face to barrel interface, in this design. Not a gun builder - yet. This means bolt face to cartridge base will never be completely uniform across the entire surface area, unless the combination of tolerance stack-up (and there are many) and co-linearity of receiver and barrel all arrive in grand harmony - like the planets. So, floating the bolt head (versus lapping or machining to achieve same, uniform contact against receiver) would appear to help with uniform application of the concussive loads axially, which would, in theory, generate a more uniform shock wave, thereby potentially increasing accuracy.

It's probably safe to assume that brass expansion/deflection at ignition will 'absorb' any co-planar tolerance issues at bolt face to cartridge base, and in so doing, absorb so little relative energy that any off-center application of axial concussive forces is minuscule. And, more likely, the tolerances in brass might dwarf this planar interface issue entirely. Of course, all this postulation is likely of infinitesimal importance to the generated shock wave, and therefore to accuracy, but is theoretically relevant. If I had time, I'd MATLAB it...

But mostly a floating bolt head appears to just improve force loading within the receiver and therefore safety of bolt retention. And maybe feels good when you operate it...

Still, rather striking how far off collinear the receiver and barrel where/are, on my gun. I should have recorded the delta in MOA when I had the chance.

Of course, much or even most of this could be merely due to inaccuracy in the location of the scope base tapped mounting holes in the top of the receiver. Or the Burris Z-rings, or the Swarovski scope, or the factory bases... But the second set of rings - the Burris Signature rings - and the second base - the Nightforce 1-piece - yielded the nearly the exact same results. Leaving the receiver to barrel co-linearity, the base mount tapped hole accuracy or the scope as likely culprits. I don't want to believe it's the scope, of course.... Those Burris Signature rings are sure a clever design.

In reflection, I might be inclined to hold the screw holes accountable, as I don't want to believe the receiver to barrel interface could be that far off, but threaded interfaces, further complicated with non-compressive bushings, are not particularly high precision in nature. Speaking of non-compressive bushing interfaces, a non-uniform compression interface here will create a stress variance that will certainly create a discontinuity, and therefore effect shock wave transmission, but it's likely so close to the effective point of application of the concussive force that it has minuscule impact.

Lots of variables here, but most are 3-4th order stuff, once you get the scope on the gun straight. Did I mention that the Model 11 260 Rem is a real sweet shooter?

And chukarmandoo, that was my concern as well, which is why I tested the technique before application. The KiWi shoe wax as a release agent really did work as well as implied in the many post out there, for me, at least. I almost got too clever by twice, with the super slippery, high-tech, government-only, non-obtainium super lube, but it failed the test miserably.

[earl39]

Mike, you are overthinking this the reason the mounting screws are off is due to the fact they are drilled and then the action is heat treated causing it to warp slightly. The floating bolt head helps cartridge to chamber alignment only.