Preface: if you're planning to do this modification, you'll probably want read the install details below!
This was fun and expensive. I had stripped out both of the little M3x0.5 threads in my forward barrel support (the parts where the scope rail threads into). The first thread partially separated when I first remove my factory rail, but I doubt that's a common issue (Murphy's Law always applies to me on a personal level).
The second thread that stripped out in that housing was caused by a scope rail prototyping test, where the hole pattern was off just enough to screw up the internal thread. It was ok for a while, but it finally gave out last week and I had to fix them once and for all!
I was already considering bumping up those threads to an M4 using Helicoils. My forward barrel support is heavily modified though, where I counterbored the muzzle facing side to seat a titanium ring that I use for my locking barrel shroud system. There was probably just enough material there to go M4, but honestly I was turned off by the idea of boring out my (3) K&L scope rails and the factory rail.
So I decided to stick with the original M3 x 0.5. There's not a lot of length to work with, and I had measure the length to be about 5mm, and I went with 4.5mm long inserts. As for the insert material, I opted for 18-8 stainless for it's strength, corrosion / rust protection characteristics.
Ordered this set from McMaster-Carr that included the drill, funky size tap, the install tool and 10 tiny little inserts. Cost was $91 freaking U.S. dollars! No idea why this set is so expensive for this particular thread size, but whatever. I pretty much needed everything in it except for the drill to install them. I also chose to go with A286 cap screws ($6.18/ea
),but man are the pretty lol
Install details:
It's pretty straightforward to disassemble the rifle; watch the the FX Masterclass video if you haven't done it before, with the following points / caveats:
Now the big eye opener for me as I was trying to chuck the first support was that I noticed right away that FX bores them at inward angles! This makes it a little bit tricky to align / indicate, so I just used the longest M3 screws that I had on hand to setup my drill/mill.
Installing the coils was pretty easy, but man are they tiny lol!
You also have to be VERY careful not to thread them in too deep - otherwise they will pop out the bottom and cause an interference issue with the barrel! I think some of the holes are actually shorter than 5mm, because I had a couple of the coils about 1/4 past flush and I wound up having to grind away the tail end of the inserts in the bore (I had already broken off the tangs).
The basic overall steps are:
Drill out the old threads:
Use the custom helical insert tap to tap the new threads:
Install the coils and break off the tang (and do not press down, just rotate them in so the tool actually contracts the coils to thread them in):
Abd of course you have to break off the tang using a punch (I used a small drill as a punch).
This was fun and expensive. I had stripped out both of the little M3x0.5 threads in my forward barrel support (the parts where the scope rail threads into). The first thread partially separated when I first remove my factory rail, but I doubt that's a common issue (Murphy's Law always applies to me on a personal level).
The second thread that stripped out in that housing was caused by a scope rail prototyping test, where the hole pattern was off just enough to screw up the internal thread. It was ok for a while, but it finally gave out last week and I had to fix them once and for all!
I was already considering bumping up those threads to an M4 using Helicoils. My forward barrel support is heavily modified though, where I counterbored the muzzle facing side to seat a titanium ring that I use for my locking barrel shroud system. There was probably just enough material there to go M4, but honestly I was turned off by the idea of boring out my (3) K&L scope rails and the factory rail.
So I decided to stick with the original M3 x 0.5. There's not a lot of length to work with, and I had measure the length to be about 5mm, and I went with 4.5mm long inserts. As for the insert material, I opted for 18-8 stainless for it's strength, corrosion / rust protection characteristics.
Ordered this set from McMaster-Carr that included the drill, funky size tap, the install tool and 10 tiny little inserts. Cost was $91 freaking U.S. dollars! No idea why this set is so expensive for this particular thread size, but whatever. I pretty much needed everything in it except for the drill to install them. I also chose to go with A286 cap screws ($6.18/ea
),but man are the pretty lolInstall details:
It's pretty straightforward to disassemble the rifle; watch the the FX Masterclass video if you haven't done it before, with the following points / caveats:
- You don't have to remove the rear trigger parts / hammer / power wheel components
- Ernest Rowe does not demonstrate how to remove the rear housing, but all I had to do was unthread the trigger linkage from its rear thread and pull it forward through the guide hole (remove the lever first using a 1.5mm hex)
Now the big eye opener for me as I was trying to chuck the first support was that I noticed right away that FX bores them at inward angles! This makes it a little bit tricky to align / indicate, so I just used the longest M3 screws that I had on hand to setup my drill/mill.
Installing the coils was pretty easy, but man are they tiny lol!
You also have to be VERY careful not to thread them in too deep - otherwise they will pop out the bottom and cause an interference issue with the barrel! I think some of the holes are actually shorter than 5mm, because I had a couple of the coils about 1/4 past flush and I wound up having to grind away the tail end of the inserts in the bore (I had already broken off the tangs).
The basic overall steps are:
Drill out the old threads:
Use the custom helical insert tap to tap the new threads:
Install the coils and break off the tang (and do not press down, just rotate them in so the tool actually contracts the coils to thread them in):
Abd of course you have to break off the tang using a punch (I used a small drill as a punch).
