Investigation: talley screws too soft or receiver 's problem?

[simone]

Hello everyone. I have just encountered an issue while mounting some Talley bases on my bergara b14 (rem 700 clone). Basically i installed the bases (talley 2 piece, aluminum) a couple months ago and the rifle was shooting very well. I didn't loctite the base screws down because i knew i could have had to swap the base screws in case i had some issues, so i just tightened them at 26 inch lbs (3 Nm), as Talley recommended me (they told me 25 inch lbs). Today i removed the bases to loctite them down and, while screwing off one of the 4 screws (the most forward one of the rear base), i noticed it was not clamping the threads (first time i screwed it on i didn't notice anything weird). When i removed the screw, there was some white grainy powder, like something coming from a chemical reaction, inside the threads and on the screw and the last part of the screw threads was stripped off, totally flattened. That's when i started doing dumb moves
I cleaned the threads, inspected them with my phone camera and a flashlight and they looked perfect. So i just tried to screw the base back in with another talley screw of the same kind (the rear one) just to see if it would have been stripped. After not much force, with my 200 euros torque wrench (recently rechecked for being accurate), I started screwing on the screw. After a few turns and not even too much force, it lost all its clamping force, I took it out, the last part of threads was stripped/flattened, again. The other screws in the other holes worked just fine and, after torqueing them at 26 inch lbs and then removing them, they look perfect. So the problem is happening only with that specific receiver hole and it happened with two different talley screws.
1) what the hell is going on with that single receiver hole? Visually its female threads look perfect
2) what was that white gritty stuff?
3) why the first time i installed the base i didn't have any issue? Everything must be related to that white stuff.

I attach a pic of rhe screw i removed from the base the first time I unisitalled it, with flattened threads and the white stuff on it. And pics of the receiver hole giving me issues from all 4 angles. Threads look fine to me.

 

[cohunt]

Is that a pre-applied threadlocking agent?

Some screws come from manufacturer with a thread locker already applied.

Have you called talley to see what they say?

Seems like it was over torqued but you said your tq driver was recently checked

 

[simone]

Is that a pre-applied threadlocking agent?

So screws come from manufacturer with a thread locker already applied.

Have you called talley to see what they say?

Seems like it was over torqued but you said your tq driver was recently checked

It was checked less than a month ago. Same screws went in and out with no issues at the same torque in the 3 other receiver holes.. i think this means the issue is in that specific receiver hole

I don't think it was a threadlocking agent and i even thought i put the loctite and i don't remember it but it's unlikely since the other holes and screws didn't have anything on them. That's really, really weird.

I sent an email to Talley

 

[Namuh]

Just a guess but it sounds like the one hole in the receiver isn't taped all the way through.

 

[quigley257]

Certainly wouldn't be the first time a receiver wasn't drilled or tapped properly at the factory. You would need a thread gage to check the hole in the receiver for proper size/fit.

 

[Allen Kitts]

Today most mounts come with some type of locking agent on the threads straight from the factory. I am betting that is what the white stuff is. The white substance could also be bore cleaner if the threads are messed up in that hole you could be getting some cleaning solution migrating up the threads.

As for the stripped out threads, I agree with @Namuh that the hole may not be threaded all the way through correctly or possibly cross threaded somehow at the bottom. Run a tap through it to see if it goes straight in and back out of if there is resistance.

Good Luck

 

[Bob Wright]

The hole may be adjacent to the barrel tenon, causing the threads to hit there.
If the hole is above the barrel tenon, you may need a shorter screw.
If you can see through the bottom of the hole then look at the end of the barrel tenon for a witness mark left from the screw.

 

[simone]

Certainly wouldn't be the first time a receiver wasn't drilled or tapped properly at the factory. You would need a thread gage to check the hole in the receiver for proper size/fit.

To me this sounds absurd. I mean, a manufacturer that messes up making simple holes in the receiver of a rifle..

Anyway, why that got worse? In the firet screw threads flattened a bit and i was still able to torque to specs, with the second and third one i tried, screws just became 100% flat in the last part

 

[Bob Wright]

To me this sounds absurd. I mean, a manufacturer that messes up making simple holes in the receiver of a rifle..

Anyway, why that got worse? In the firet screw threads flattened a bit and i was still able to torque to specs, with the second and third one i tried, screws just became 100% flat in the last part

It happens.

 

[simone]

It cou

Today most mounts come with some type of locking agent on the threads straight from the factory. I am betting that is what the white stuff is. The white substance could also be bore cleaner if the threads are messed up in that hole you could be getting some cleaning solution migrating up the threads.

As for the stripped out threads, I agree with @Namuh that the hole may not be threaded all the way through correctly or possibly cross threaded somehow at the bottom. Run a tap through it to see if it goes straight in and back out of if there is resistance.

Good Luck

I didn't use bore cleaner, maybe some combustion residues! Who knows. And there was also black stuff filling the threads, i don't know if you noticed it, there is an arrow pointing at it in the pic

 

[Allen Kitts]

Sorry I did not se that part. Very weird almost looks like plastic.

 

[MtPockets]

I could be wrong, but dont the threads in the reciever look flat? Could it have been drilled with the wrong size bit, then tapped?
If you have a set fine drill bits, see if the ID of all 3 holes is the same.

 

[tobnpr]

Get a #6-48 taper tap and chase the hole, then try a new screw.
Clearly, the tapped threads in the receiver are the issue since a new screw got effed up...

 

[simone]

I could be wrong, but dont the threads in the reciever look flat? Could it have been drilled with the wrong size bit, then tapped?
If you have a set fine drill bits, see if the ID of all 3 holes is the same.

I don't see flat threads but a borescope would be useful