Gunsmithing Sako TRG Scope Mount Threading

[.50 Cal Cow]

Went to remove the factory picatinny rail from my Sako TRG to swap from the factory 0 MOA rail to a NEAR 25 MOA rail. Using a properly fitting hollow ground screw drive I managed to get two of the four screws out but the other two would not budge a bit even after carefully applying heat with a variety of methods. Took it to a local gunsmith with a good reputation who has called and said that he was able to remove the heads and the rail. HOWEVER, when he drilled/tapped the screws to attempt to remove them they will still not budge and he would be on the verge of snapping his tools. It seems that I will have to look at rethreading these two holes (not quite comfortable with but...).

Looking for some info or advice from anyone with experience.

Does anybody know what size threading/pitch is used on the TRG? He is unsure as none of the metric sizes he had on hand seemed to fit. He mentioned he could order the tools once we could confirm the thread size but it would awhile for the tools to come in.

He has offered that he could rethread all the threads to a standard size threading ie. 6 40 or 6 48. Would there be any cons to going this route?

I'm not looking to cheap out and willing to wait to get it done right just not enough experience on this matter to know if there's other things I am not considering going each route.

 

[Mr Joshua]

Re: Sako TRG Scope Mount Threading

What I did was I drilled the screw with a large enough drill bit to remove the head of the screw. Only the threaded portion of the screw is left so you are able to lift off the old rail. The rail will be ruined however. Once the head is gone there's no load on the screw so just get a dremel tool and grind a slot on the top of the screw shank and unscrew with flat tip. Unless red thread locker was used it should come out very easy.

 

[.50 Cal Cow]

Re: Sako TRG Scope Mount Threading

Thank you for the suggestion. Unfortunately it looks like I'm/gunsmith are beyond this point. Whatever epoxy or locktite material that was used was used in either such gross quantity or is just that strong that it is not budging.

 

[Cesiumsponge]

Re: Sako TRG Scope Mount Threading

The factory Sako TRG receiver screws are M3.5 x 0.6mm pitch, a very oddball size. I only found one place that sold socket cap machine screws in that pitch since I planned on using a socket cap screw as a mounting stud for an AI mirage band rather than buying the overpriced factory set. Your gunsmith might have to order up special tooling since it's not a normal size.

When I purchased my TRG, I had Eurooptics remove my picatinny rail so I had access to the dovetail to run a Spuhr mount. You might want to PM them and see what methodology they used to soften the epoxy. Maybe they just applied a ton of heat.

To remove the leftover epoxy on the top of the receiver when I took delivery of the rifle, I used aircraft remover (mainly methylene chloride) to remove the epoxy junk. You can get that at any auto parts store, but it's typically a thick gel so it wouldn't seep into threaded holes.

 

[Spuhr]

Re: Sako TRG Scope Mount Threading

Removing rails are normally pretty easy just add some heat so the glue dont hold the screw.
I would drill a small hole in what is left of the screw , put a torx bit in the drillpress , heat the screw and unscrew it with the drillpress kepping the torx bit into the hole in the screw.
Works fine mostly time.

Håkan
Ps. Don't turn the drillpress on!

 

[cwinston]

Re: Sako TRG Scope Mount Threading

If the screws didn't come easily when you applied heat, you didn't heat it up enough. I had that same problem on my TRG. Once I hit it with enough heat, they came out very easily.

 

[.50 Cal Cow]

Re: Sako TRG Scope Mount Threading

Thanks all. Rail is off and screws are out. Purely a matter of heat.

 

[Quarter Horse]

Re: Sako TRG Scope Mount Threading

What is te best method of applying heat and how do determine when you have enough?

 

[2156SMK]

Re: Sako TRG Scope Mount Threading

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Quarter Horse</div><div class="ubbcode-body">What is te best method of applying heat and how do determine when you have enough? </div></div>

A torch.
Experience will show you when certain parts are getting hot enough.

Say you have a broken off screw sticking up out of a part.
Shield the base metal and heat the screw from the side so as not to also heat the base metal.
When the screw just starts to turn colors on the edge, it's way hot enough.
Twist it out while it's still smoking hot.

 

[2156SMK]

Re: Sako TRG Scope Mount Threading

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Spuhr</div><div class="ubbcode-body">I would drill a small hole in what is left of the screw , put a torx bit in the drillpress , heat the screw and unscrew it with the drillpress kepping the torx bit into the hole in the screw.

Don't turn the drillpress on! </div></div>

That last part is real important!

It's amazing how good drill presses and milling machines are at removing screws under just hand power.
Using the quill to hold the drive bit, you have such positive alignment and such presure into the fastener that the bit can not slip out.
The only option the screw has is to rotate...

 

[Hellbender]

Re: Sako TRG Scope Mount Threading

One of the little $5 Butane powered "pencil torches" sold many places work very well, and you can direct the heat to a small pinpoint (like a screwhead).

 

[knife edge]

Resurrected because I had to go through this and... its all about me.

I lightly preheated just the rail with a map gas torch. I then took a slotted tipped soldering iron and held it on each screw for several minutes, applied more torch just to that screw and rail until I saw a wisp of smoke. The screws would then come right out with a slotted screw driver. Think gallons of red loctite... heat breaks down loctite. Dont get the receiver too hot or that heat could transfer to the chassis and potentially melt the plastic panels. My chassis between the receiver and rails never got too hot to touch.

Lates

 

[Mrcrask]

Had no problem removing screws , but the base would not come off my Trg. Is it loctited to the base as well? Afraid to put to much pressure on it to remove it. What did the trg owners end up doing to remove theirs. I’m guessing heat gun??

 

[Gene Poole]

Clothes iron setting on the rail for a few minutes ought to do it.

 

[cwinston]

Yes, there is typically loctite between the rail and action, and it is pinned as well. Once the screws are out, a few taps with a punch on the rail should knock it loose.

 

[dttheliman]

Been there done that got the T-shirt - the screws are odd to say the least a M3.5 x 0.6mm pitch (and they were a pig to find) and they have a healthy blob of genuine Finish thread locker on them - While getting that rail off, I managed to shear the front screw head off, anyway it was a clean shear and the rail popped off with minor persuasion (couple of taps with a brass pinch and small hammer - its pinned as well) so ended up looking at this 'effing screw sheared off flush with the action - carefully center punched that stub and with a small drill in my Foredom and steady hand I got it opened up ran a couple of larger drill sizes into the hole enough to get a disposable torx bit to tap in + a couple of seconds with the smallest torch and oxyacetylene and it hand turned out - luck was with me that day - the front screw is right above the barrel threads and being stupid with the drill could have caused me issues down the road- installed a one piece 20moa sako mount and life has been good since then. I have 2 or 3 of the sako screws in my tool box in case anyone gets real stuck .

 

[northern50]

M3.5x0.6mm screws are hard to find, until I was digging through my box of lathe insert screws and found the correct one.. you can buy them from Shars tooling for relatively cheap, availability is good and they come in a torx head. Using a drill press for holding a screw driver bit square to the action for screw removal is a sweet trick and has saved me a lot of agony over the years, especially with flat head screws.