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First M-70 Extractor Cut (w/Pics)

Carlsbad, where would you provide more clearance? Seems to me there's no good reason to expose any more of the case than just the extractor groove and no more width than that of the lug race. You can just see the case wall peeking out in INTJ's job and that's as far as I'd go.

If it were possible to exactly match the profile of the front of the extractor, theoretically it seems, the clearance wouldn't need to be any more than the rest of the bolt nose.
 
Gotcha. Getting the cut to line up with the lug race has been my biggest struggle too.

And, to ditto WSMNUT, looks like you're good to go INTJ.
 
polish your shoulder helps make sure it tightens to the same location every time. I use a torque wrench and get good repeatability. But if it is for someone else, you'd be surprised how often the first thing they do is take it apart and inspect it.
 
INTJ- any time you only have to do a little file work, you've won. As stated above, getting the extractor cut perfect the first time is, at best, a sometimes thing. A small witness mark on the bottom of the barrel/receiver face when it's tightened to final torque will allow anyone to later remove and reinstall the barrel correctly timed.
 
I learned a bunch with this. The Pre 64s and earlier Classics used a tapered extractor cut, the layer Classics and New M-70s used a straight across cut. While it looks like the tapered cut provides more support to then case, it doesn't. Both types cut the cone down to where the chamber starts, and measures about .205".

It's the just tapered slot is cut with a wheeled cutter and with the wheeled cutter the only option is to taper it or cut two slots like an H-Ring Mauser. The only way I can see to get a perfectly flat cut is with a horizontal mill or else a fixture to hold the barrel vertically in a regular milling machine. I guess a Palmgren on a Lathe might work too.

I also had success marking the slot by putting Prussian Blue on the face of the extractor and then pushing it into the barrel with the barrel fully tightened.
 
Stan Taylor said:
Don't you just love it when the engineering guru's at Browning and Winchester change the thread pitch on these actions 28 TPI I think that was a bad brain fart myself.LOL
Click to expand...

I think they did it to get more material around the chamber for the .550 diameter cartridges. Although there didn't appear to be any issue with a 1" x 16 TPI, a 1.062" x 16 is better. So I guess a 1.062 x 28" would have even more material around the chamber.
 
INTJ said:
I learned a bunch with this. The Pre 64s and earlier Classics used a tapered extractor cut, the layer Classics and New M-70s used a straight across cut. While it looks like the tapered cut provides more support to then case, it doesn't. Both types cut the cone down to where the chamber starts, and measures about .205".....
Click to expand...

I believe the early style tapered, convex profile cuts were to cam the extractor away from the case head at final lock up.
 
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