Mosin Nagant sniper rifle scope. Having problems, need help.

[SmileDocHill]

Short version: Anyone VERY knowledgeable with PU sniper scopes? I would like to have this looked at by someone who has been there, done that.

I've gotten great groups with this rifle in the past and recently so I know the rifle itself groups well. I took it to Talladega marksmanship park this last weekend and the groups started opening up randomly and wildly after a couple hours. I noticed the main screw coming loose and bagged it up. I wasn't going to spend time at the range trying to figure out and fix the issue, I had other rifles I wanted to shoot and my shoulder was already getting tender.
The big screw at the base looks like it is meant to be able to be tightened by hand (based on the large diameter) but also has a flat head screw slot in it. I tightened it down by hand and it didn't come loose again but only shot about 10 more rounds before realizing the futility of shooting more when I don't really know if my scope is not moving.

 

[NKBJ]

All ears here. Been thinking about looking into those scopes. The mounts looked like a most mysterious set up so I'm still in the bleachers.

 

[SmileDocHill]

Yeah, it is a strange bird on many accounts. The elevation and windage adjustments actually move the reticle in the field of view. Meaning, if you have a lot of windage dialed in the "crosshairs" will actually be positioned to the left or right in the sight picture.

 

[Hop]

Bring it on Saturday. We'll see if we can figure out what it's doing. Both of my Mosin are iron sights though so I'm not real familiar with the scopes.

 

[DoggyDaddy]

Paging MillerTyme...

 

[knutty]

Sounds like you already figured it out, the mount screw came loose. I use a big flathead screwdriver to torque it down. You will probably notice a couple witness marks, one on the screw head and one on the mount base that were struck by the Soviet armorer so it would be noticed if the screw backed out.

If your scope really is having issues, there is a guy on gunboards that used to work on PU scopes. Not sure if he is still doing it anymore though.

 

[Miller Tyme]

Paging MillerTyme...

Damn, i thought i posted to this thread several days ago, my bad.

OP, the large thumb screw can be tightened with a screw driver,( tip of the bayo works great) and a little "removable" loctite helps. If the scope setup is arsenal set up at least one (sometimes both) elevation screws should be staked holding the mount securely along with the thumb screw. Once it is set there is virtually no reason to ever remove it from your rifle. I have shot my 43 Tula PU for over 4 years and have never removed the mount and shoots pretty nice out to 850 yds.