If finger tip pressure on a scope base overhanging the taper on a barrel moves the base up and down, stop and think what happens to your scope and rear scope ring during recoil.  

 Take the flexing out of the base for more secure scope mounting and less strain on your scope and scope rings. 

 Adding a screw contacting the barrel at the extreme forward tip plus a screw INTO the tapered part of the barrel stabilizes the tip of the base and stops vertical flexing of the scope base during recoil.  

 Barrels with muzzle brakes that depress the muzzle during recoil compound the strain on the base, scope, and rear ring especially.

Here is an example of vertical stringing of shots due to the unsupported portion of the scope base flexing as reported by Blaine D.

"When attempting to sight in my 338-06 barrel (at 100 yards), it was obvious that every shot was hitting approximately 1" higher than the last one. After about 6 shots, I had to spin the turrets on my scope to bring the bullet impact back on the paper. 5 more shot fully confirmed that the bullet impact kept hitting about an inch higher each time. Bullet impact also gradually strayed to the right about 2" during all of this. At this point, I noticed that the gap between the barrel and the bell objective was smaller than when I first mounted the scope. When you mentioned tension on the scope tube, everything clicked together and made sense. At first, I couldn't figure out how the base could move, but yet still remain tight and solid. Based on your remark, I reasoned that the when the base is flexing during recoil, the scope tube is probably shifting in the rings, but does not shift back after the recoil. This creates tension between the scope and the base, resulting in the base being held in a stressed state. This also results in the scope pointing downwards more with each shot. This would explain the upward vertical stringing. I took pictures of my scope, particularly the gap between the bell objective of the scope and the barrel. I measured the gap between the barrel and the scope itself (not the rubber cap) using feeler gauges. It measured 0.119". Then I removed the top half of one the rings to relieve any tension. I felt and heard a distinct pop as the rings shifted position on the scope as soon as I loosened the rings. I remeasured the gap, and it measured 0.150". The gap widened 31 thousandths of an inch! No wonder the bullets keep continually walking up the target with each shot. The tension in the scope tube was pressing and holding the tip of the base down more and more with each shot." 

The steel Burris base is potentially more rigid than most aluminum bases, but in spite of this, note the gap between the front bell of the scope and the barrel in this top picture, then note how the gap has closed after shooting. 

See the inset close ups in the upper right corners of the photos.


                                                                                                     Now, note how much smaller the gap is below the bell in the photo below.


                                                                                  Flexing the scope downward stresses the scope tube and the rings.

                                                             The scope cannot return to its at-rest position. Poor design choice, and for no logical reason.

Here is how I solve the problem by stabilizing the front tip of Weaver-type and EGW picatinny rail scope bases that overhang the tapered part of the barrel. 

 Note the small headless set screw through the far left end of the base. This screw just contacts the surface of the barrel. 

The next screw from the left is threaded INTO the barrel. 

 NOTE: Locations of the two front screws varies from photo according to the application.

Pictured is the Weaver #410 base modified so the front tip is anchored. We give the picatinny rails the same treatment to eliminate the "diving board" effect. 

 Anchoring the front tip stops both the flexing downward as the barrel moves up in recoil, and if there is downward force on the barrel from a muzzle brake, the screw INTO the barrel opposes it.  

 The front tip of the scope base overhanging the tapered part of the barrel is held rigidly in place.  

 In the style of mounting pictured here, one more screw is added at the point just behind where the taper of the barrel begins..... what we refer to as "6-screw" attachment, 5 screws in the straight shank of the barrel, plus 1 into the tapered part of the barrel.

Screws used are Weaver-style "oval head" screws, not flat bottomed "fillister head" screws that can shift..

I have become pretty hard nosed over the years when it comes to using flat bottomed head screws simply because the base can move a few thousandths in any direction due to the clearance around the screw shank and nothing to keep the head itself centered.

  At a minimum, if I do use a flat bottomed head screw I put a tapered seat in the base to center it. But I prefer to use the Weaver style screw, "V" head in a "V" seat so the base must stay centered and cannot shift.

  This may be a minor detail that may or may not show up on paper, but fundamentally the security of a "V" assures the base cannot move in any direction.  

 Muzzle brakes that have the ports angled back DO in fact put a fore and aft strain on screws and scope rings, creating more potential for the base to move front to rear, rear to front with each shot.

It's all about doing things as right as theoretically possible. 

 Do this simple test with Weaver style bases installed with just the standard 4 screws!


Place one finger against the front end of the base at the gap where it overhangs the taper of the barrel.  Now, with or without a scope on the base put finger tip downward pressure on the front tip of the base with the other hand.  When you release that pressure, you will feel the base flexing upward  ...... as obvious as a train wreck!  This is just finger tip pressure. 

Stop and think about the sudden force of recoil upward.  If the base is flexing, the scope has to be flexing with it, and you have all that leverage being applied to the rear ring..... and the scope tube, too, of course.

Add to your barrel purchase from us either EGW picatinny rail or Weaver base installed with front tip of base stabilized $59, billed separately, base included. Picatinny base installed with front tip of base stabilized $79, base included.

Note that hole patterns added are not "standardized". I vary the hole pattern according to the application.

Picatinny bases are 3/4" longer & provide more eye relief. 

Click here. More eye relief and more places to position scope rings as well as locations for adding more scope rings to keep the scope from slipping in recoil.

6-screw Weaver scope bases on UNtapered barrels still $49

This applies ONLY to the UNtapered, straight, Contender S-14 type barrels, current production "G2" barrels, and UNtapered Encore custom barrels where the untapered shank of the barrel is AT LEAST 3 1/2" long so as to provide support of the base at all 6 screw locations.

Mike Bellm

 email: [email protected]  

Phone: 541 956-6938

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