As you can clearly see from the pix below, this new custom Encore barrel put out by one of the big name shops clearly demonstrates that you cannot use the normal 6-screw spacing on tapered barrels.
Here you can see a stainless plug screw backed out to the same plane as the straight shank of the barrel over the lug.
It should be as obvious as a train wreck that the screw located on the taper of the barrel will bend the scope base downward.
However, this new barrel came from this premier, big-name after market barrel maker exactly as you see it.
Viewed from the top
Having more than 4 screws has its merit, and I do convert and install bases with more than 4 screws, but there is a right way to do it.
First, for 6 screws with the spacing shown, it must be done on a barrel with a longer straight shank or a straight barrel with NO taper.
When I do install a base with more than 4 screws, I normally only add 1 screw ahead of the standard 4.
The spacing between the short spaced pairs is .836″, the common pattern used originated with untapered Contender barrels and is simply another pair “leap frogged” forward of the original 4.
Note that the 5th hole from the rear is right on the breaking point where the barrel begins its taper so that it, too, may tend to bend the base some.
When I install a 5th screw I locate it at around .7″ to .750″ forward of the original 4 screws, staying back behind where the taper starts.
The above is an example of why you cannot use these 6-screw bases with 6 screws on tapered barrels such as tapered Contender 10″ barrels and any of the production TC Encore centerfire barrels
Here is how I anchor the tip of the base so it cannot spring up & down.Click on this link to see how I run one screw down to TOUCH the taper of the barrel, then add the 6th screw INTO the barrel so the overhanging part of the base cannot spring up and down with each shot, cause vertical stringing of shots, and add stress to the scope tube.