Concerning screws that consistently work loose

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I bought a Browning Challenger last summer, which is a beautiful and very practical 22lr pistol. There are two drawbacks of this particular model one being the single screw attaching the rear sight to the barrel will not stay tight. Naturally this affects trivial things like accuracy. In the photo below is a sample of which I speak, and immediately above the letters "PQ" is where the offender is supposed to snugly reside.

As I have tried Blue Loctite, are there any slightly stronger alternatives or homemade concoctions that will prevent a screw from rotating on it's own? I am not interested in more permanent solutions like Red Loctite for inevitably the sight strap will have to come off for the occasional thorough cleaning of OCD degree will be necessary.

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In the event that someone is curious, the second fault in the design that I have found is relative to the slide stop/release. Browning built it to fit in a slot and held in place by it's own working spring and the left grip. I expect the problem is unique to those with the synthetic (and quite flexible) grip, and the stiff wood gripped models would enjoy immunity from the stop/release, not always stopping the slide on empty magazine.
 
First clean the threads really well. Loctite does not work that well if the threads are not clean and dry.. use acetone or lacquer thinner. Then a little blue Loctite and tighten the screw. I have not had to use Loctite if the screw is clean and tight. Tight being the operative word.
 
Thank you guntech, it is likely I didn't apply the blue Loctite on threads properly cleaned. I'll obtain the mentioned cleaner, and try fastening "tightly". Correct tension for screws this size would be in the vicinity of 16in/lbs?
 
Alchool and a q-tip has worked well for me, clean the female and the male threads.
THIGHTEN the screw, that will set the Loctite.

As the good ol joke goes..............Tighten till it breaks...and back off a half turn........
 
Tight for me is the object held in padded jaws in a vise and two hands on the screwdriver which fits the screw properly... lots of my weight on the screw... don't let it slip, stop when you can't move the screw anymore without deforming the slot...
 
And that level of tightness isn't the sort of thing we should be doing on a small size screw. The correct and maximum torque for #6 and smaller screws can be easily delivered by two fingers on a screwdriver that is otherwise held firmly in the slot.

What I'm seeing on that sight bar is a VERY long arm that simply will not be correctly locked in place by a single screw and no other locating features. A proper way to secure that sight bar would be to have the bar fit into a recess on the barrel which is a firm hand press fit. Then the only, and proper, job for the screw is to hold the bar in the slot.

As it sits now there is very obviously some side to side movement which is allowing the screw to work itself loose. Either that or the threads of the screw or slide are partially stripped so the screw is working loose under the pressure and leverage involved. Other methods for keying the sight bar in place would also be good. It just depends on how well the bar is located and supported. There IS a lot of leverage there and not a lot of overlap with the barrel assembly to support that length of arm.

Which would also be why the new Buckmarks got away from this style of sight and either use a more firmly mounted rail or a sight which mounts onto the rear of the slide. It's a nice idea to put the sight onto a solid part of the gun. But as shown it's a rather delicate solution that puts significant strain on the attachment and locating features.
 
Don't know if you fish or not, but what I use on loose screws is 2lb monofilament fishing line. Remove screw, insert a longer than needed piece of line into screw hole(it's cheap), insert screw and slowly tighten. Make sure you use the proper size screwdriver or you can bugger up the screws. The extra line will either fall off or can be clipped off.

It may take a couple of tries to figure out how little line is needed to still be able to seat screw flush.
 
All that being said it is a very uncommon problem with that pistol...
My discretion of tight was with that particular screw, not every screw out there... but Weaver slotted 6 x 48 screws will take that much torque. Torx tips will break before reaching that level.
 
kanook said:
Don't know if you fish or not, but what I use on loose screws is 2lb monofilament fishing line. Remove screw, insert a longer than needed piece of line into screw hole(it's cheap), insert screw and slowly tighten. Make sure you use the proper size screwdriver or you can bugger up the screws. The extra line will either fall off or can be clipped off.

It may take a couple of tries to figure out how little line is needed to still be able to seat screw flush.
Click to expand...

This would probably fix your problem. Many years ago, Ruger had a problem with screws working
loose on their large caliber single actions. The cure was that they put a little nylon plug in each screw.
It worked and did not lock the screws in place.
 
Apply the blue Loctite to both the screw thread and the bottom of the rib where it sits in the recess on the barrel.
 
It is a long strap overlapping the receiver by about 1/2". While not being in a grooved slot on the receiver, the receiver's top is curved and the strap to match. The rear of the strap does ride in a square channel atop the slide and the elevation screw is at the very rear - this adjustment works by the screw working against the top of the slides channel so higher elevation theoretically applies greater stress on the holding screw... but it is still 3 1/2" away toward the front.

Once I obtain the proper cleaning agent, I'll carry on with guntech's recommendation and expect that should suffice. Thanks to all who responded whose suggestions will likely come in handy in other applications as well.
 
There is a loctite primer that is used on what loctite refer to as inactive metals.It will work for you and keep the screw installed where you put it. I sharpen expensive "shears" $100.00 + a pair known as scissors and use the primer when needed on the pivot screws.When it does its job removal is still possible but that screw isn't coming out on its own. I am inclined to believe that the threads wern't clean enough for the loctite to cure. Brake clean will get the gun prepared for loctite. If there is plating the metal is referred to as inactive. All this info is available on the loctite web page.

R
 
tjhaile said:
Apply the blue Loctite to both the screw thread and the bottom of the rib where it sits in the recess on the barrel.
Click to expand...

This is where I would suggest as a start. Clean the whole area with acetone or similar solvent to remove all oils, and ensure that a little of the locking compound finds it's way between the sides of the sight extension.

I would expect that the forces at work during the recoil cycle would be snapping the long extension sideways a wee bit, and that is going to cause the screw to get undone.

May well that the solution lays in a combination of all or at least several, of the suggestions.

I think it'd be a pretty cool thing to see what that sight goes through on a high speed video camera.

Cheers
Trev
 
Vibra Tite VC-3 is a thread locker as well. You clean the screws, apply the V3 and allow to dry before you put the screw back in and it is reusable. You have probably seen this on gun screws from the factory. I had a sample and it worked well but I have not had the urge to drop $30 on a small bottle. You can get it from some of the auto supply stores in Canada although they may have to order it in. Fastenal.
 
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guntech said:
Yuuuuuuch! Home gunsmithing at it's finest...

You could always add a big gob of epoxy on top too...
Click to expand...

I was thinking about taking a 7014 rod and stick welding it in place... or for an even more impressive finish, a lovely gob of melted brazing rod plus the colour case hardening that will accidentally result from the procedure. Thk

Seriously though, I just need to get some acetone...
 
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