Mark IV Rear sight missing set screw

[BMEGP100]

After every 200-300 rounds I find that the rear sight set screws back out. I have cleaned the screws and used blue locktite, but this keeps happening. I am cleaning the set screws before using the locktite. I know that I should also be cleaning the threads in the barrel, but the holes are too small to do anything other than dropping in some solvent and trying to absorb it with a tiny piece of cloth. Any suggestions?

This week one of the screws must have fallen out while I was shooting. I couldn't find it. Do you think Ruger would sell me a set screw and maybe a couple of spares?

 

[hittman]

Ruger will likely send you screws for free.
Will probably ask your serial number.

Try fishing line around the screw in the grooves.

 

[mirglip]

In the meantime you could check ACE Hardware, they have a drawer marked gun screws.

 

[contender]

Call Ruger,, they will help.

The fishing line trick is easy. Take a piece of mono fishing line,, stick the end in the hole,, add the screw,, tighten the screw,, use a lighter or lit match to "cut" the line near the screw head.

 

[Mobuck]

To clean those tiny blind hole threads: spray some 'brake parts cleaner' in the hole and blow dry with compressed air. Guaranteed to work. Will leave the hole oil free, dry, and clean. Don't over apply the thread locker.
Also, NEVER put the thread locker in the hole. Only put a tiny drop on the screw threads.

 

[BMEGP100]

Thanks for all the replies. I will use brake cleaner and the air hose to clean the thread holes. I am going to call Ruger on Monday to ask about replacement set screws.

 

[Johnnu2]

Use a Q-Tip or three as well,

J.

 

[s4s4u]

M3x0.50, 6mm length

 

[hittman]

These Gum brand flosser thingys work good in the tiny holes too ….. I buy mine at Walgreens or Dollar General.

 

[BMEGP100]

Use a Q-Tip or three as well,

J.

John, thanks for your suggestion However any Q-tip is way, way too big for these tiny threaded holes.

 

[BMEGP100]

M3x0.50, 6mm length

Hawkeye, thanks for the size info.

 

[BMEGP100]

These Gum brand flosser thingys work good in the tiny holes too ….. I buy mine at Walgreens or Dollar General.

View attachment 97139

Hittman,
Is this for cleaning the threaded hole or for use as a thread locker instead of blue loctite?

 

[hittman]

Cleaning

 

[BMEGP100]

Thanks for the suggestions. I called Ruger last week and they sent me a set screw to replace the one that was lost. They included two extra ones. No charge. Great customer service. They did ask for my serial number.

Now to cleans the internal threads.

 

[contender]

Glad you got it fixed. And not a big surprise that Ruger helped you out.

 

[Hertervillian]

I have had zero luck keeping set screws in any adjustable sight, on any pistol I own. I’ve cleaned with brake cleaner, blue loc tighted, center punched you name it. I fully expect that rear sight to move and fall off.

 

[Uncle Howie]

I have had zero luck keeping set screws in any adjustable sight, on any pistol I own. I’ve cleaned with brake cleaner, blue loc tighted, center punched you name it. I fully expect that rear sight to move and fall off.

I’ve only had the occasion to remove one adjustable rear sight from a MK II, but it wouldn’t have fallen off (or even moved!), in a hundred years!

After loosening the set screw, I tapped (left to right) gently. Seeing no movement, I got a bigger hammer, and tapped it with more authority. Still no movement. Finally I got a bigger hammer yet, and beat the daylights out of it. Slight movement!

It took very firm tapping (beating, really…) the width of the whole dovetail, to finally get mine out.