Scope mounting question

[Atroxus]

I recently mounted a Bushnell .22 rimfire scope on my Marlin model 60. I *thought* I had tightened the screws down pretty tight. When I sighted in last week at 50 yards my best 5 shot group was barely over an inch across. Today I took it to another range and was shooting at a distance of only 25 yards, and my shots were all over the place. By the end of the 200 round session all were hitting far right and low of point of aim. When I got home I realized that somewhere along the line the scope had slipped back far enough that the rear mount was completely OFF the end of the mounting rail. Anyone have any idea how to keep this from happening again?

The picture below shows the screws on the scope. I am wondering if I need a special screwdriver or driver bit for a drill to get these tightened enough? The widest screw driver bit I own still only made partial contact due to the big hole in the center of the head slot, so I tightened it as tight as I could without risking stripping the screw heads. Apparently it was not tight enough.

[AWS]

Take the screw to somewhere like Tacoma screw and see if they have the correct bit or a replacement screw.   I have noticed that some of the import rings seem to have a Torx head size all their own and some of the Weaver ones are very shallow.

AWS

[Huntbear]

Any store that sells shooting accessories Cabelas,etc.... carries basic gunsmithing screwdriver sets.  They run 20.00.  Get ya one.  It will have the bit  you need.  Also, a touch of RED locktite on the threads will keep em from loosening up after you get them tight.

[high country]

did you snug the bases before the rings? if not there could have been torque that prevented the bases from getting tight. as mentioned locktite is a good plan....I use blue as red is there till you get it hot, blue is removeable. if you are worried about it you can add a wee bit of shoe goo or e 6000 to the scope and rail contat points. this is common on big kickers, not so much on a rimmie

[JackOfAllTrades]

I use a Quarter with those type of turn down nuts.  If the stud gets in the way of the center, there's no gunsmith bit/screw driver set available in that format that I know of.  Shortening the stud is the next step, or filing a notch in a Quarter will do the job too. A little locktight is a good idea too. Better yet is a better set of rings. The rings that come with rimfire scopes are lower quality budget minded mounts. Step up to a higher quality ring with allen screw hardware.

-Steve

[Shootmoore]

What Jacko said, also use BLUE locktite not red.  Trust me if you ever have to remove the scope you will be sorry if you use red.

Shootmoore