Need help tying down an ornery scope.

[amlevin]

I have a fairly heavy scope, a 12-42x56mm NXS Night force scope mounted on a Remington Stainless Steel action. I have a Picatinny rail mount secured with 4 6-48 screws torqued to 20 in lb and lots of blue loctite. The screws and screw holes were degreased prior to applying loctite and torquing.

The rifle is a .308, not necessarily one of those noted for heavy recoil but for some reason I can't seem to keep the screws tight.

Any suggestions before I drill out the mount and action for 8-40 screws. Don't want to go to red loctite for obvious reasons but I have considered just rebedding the rail using a well degreased action/rail, and some devcon. Essentially just bonding the rail to the action semi-permanently. :

I'm open to just about any solution short of tig welding but ?????????? I'm getting tired of having to remove the scope and retorque before every range session.

 

[Preacher]

LOTS of Blue Loctite really is not needed, just a dab will do ya, just like the old Brylcream ad....
Have you checked to make sure the base is level on the action ??
Red Locktite can be removed with a application of heat, but again, a little dab will do ya....

 

[amlevin]

LOTS of Blue Loctite really is not needed, just a dab will do ya, just like the old Brylcream ad....
Have you checked to make sure the base is level on the action ??
Red Locktite can be removed with a application of heat, but again, a little dab will do ya....

The base is actually bedded to the action. Same method as with an action. First fitted base with some prussian blue. Then applied a skim coat of Devcon and using screws for locating purpose only rubber banded the base to the action with just enough pressure to squeeze out excess Devcon.

After the Devcon cured I then parted the base from the action, cleaned up the excess epoxy, and secured with screws torqued to the usual specs.

Hoping that either the base stops loosening or I can find a way to overcome the issue.

 

[Preacher]

Seems like you have that covered 100% the way it should be..
Are the screws full length in the holes ??
Try retapping and drying the screws and holes, and then replace the screws with just enough Blue to notice that it's on the screw, torque them to specs and let them set overnight and see how that works out..
If that don't help the problem, then it's time to do the 8x40 part.

 

[amlevin]

In researching Loctite thread locking compounds I noticed that the traditional "Blue" comes in two temperature grades.

The Geeral Purpose primerless (P/N 243) shows a break torque of 106 in/lbs and prevailing torque of 26 in/lbs.

The High Temp version of the "Blue" (P/N 246) shows break of 170 in/lbs and prevailing torque of 48 in/lbs, almost twice the torque retention of the standard "blue".

Has anyone ever used the P/N 246 Loctite? It appears to be a way to get more "thread lock" without having to step up to the "Red".

 

[jonbearman]

I agree with preacher,but I would use 271 loctite.If it is degreased with brakekleen or something,still make sure the holes are dried out completely before using the 271. That is the red that bruce is referring to.

 

[hogpatrol]

I use CRC contact cleaner on the holes before blue loctite. Some degreasers leave a film that will interfere with the loctite doing its job.

 

[JRS]

Have you checked the screw length? Like Preacher asked, are the screws full length in the holes?

 

[Preacher]

I degrease the holes and screws with Isopropyl Alcohol and never had a base come loose....

 

[amlevin]

Have you checked the screw length? Like Preacher asked, are the screws full length in the holes?

Yes, plenty of screw length. I'm very anal about the "diameter and a half" rule I learned while working for a really big aircraft manufacturer.

I'm headed to the range tomorrow so I'll be checking everything. It will be interesting to see if anything loosened after the last weeks session. If it has, I'm going to trigger the "nuclear option" and just "glue the whole mess together". Bond it with devcon and deal with the hassle of removing it in the far future.