Gunsmithing RC and correct filler rod for fixing extraction camming surface

[NineHotel]

Does anyone know the correct RC or specific TIG filler rod for adding material to M700 receivers and bolt handles? My extraction cam surface needs reworked and I was considering adding metal via TIG then fitting from there. Thanks.

 

[Thud]

How do you know you have a problem in that area.

 

[mudpig]

It'd be a lot simpler to reposition the bolt handle to get correct bolt timing and primary extraction.

 

[NineHotel]

I found this - Matching annealed strength: If the 4130 steel is in the annealed condition (the recommended condition for welding to avoid cracking) and will not be post-weld heat treated to increase material strength, using a filler metal with comparable strength properties is common and acceptable. For an approximate match to annealed strength 4130 steel, low-alloy filler metals offering 80 to 90 ksi tensile strength would be appropriate. These filler metals provide the advantage of a strength match in the weld deposit without the crack sensitivity of a chemistry match. See Figure 2 for filler metals that can be used for this option.

 

[NineHotel]

You can visually see that there is very little contact between receiver and bolt handle; the bolt handle looks a bit worn just on that one spot. It does not look like it makes good contact.

Lugs were lapped in, which can contribute to the lack of engagement in this area.

I'll consider the repositioning option as well thanks.

 

[Ledzep]

Much easier and less at stake to pull the handle off the bolt body, build up weld on the cam surface (of the handle) if necessary to reprofile it, then time it and re-solder and potentially weld the handle on.

 

[NineHotel]

OK I just checked the bolt/body clearance vs 2 other 700s - this one has quite the gap, hence the reason it is making so little contact at the last moment, causing this one spot to finally wear to the point of being a problem.

I also answered my own question above - receiver is 4130, bolt body and handle are 4140, should have no problem adding some material via tig or welding the handle on should I go that route.

Thanks all!

 

[Gene Poole]

Are you planning on annealing the receiver and re-heat treating it?

I'd just go with a PTG aftermarket bolt handle. It has a lot more camming surface.

 

[DAVETOOLEY]

Dan's done thousands.
http://accu-tig.com/

 

[FCrifles]

^^^