Winchester Model 70 tenon cutout

[Kck]

A customer brought me a Winchester Model 70 Laredo to chamber in 7mm STW and this will be my first Winchester project and I'm in a bit of a quandary so time to ask the pros again. I broke the current barrel loose and it's got a cutout in the tenon threads for, what I assume to be, the extractor claw. However, I can't find much info on this and most of the Model 70 chambering/tenon info I see doesn't show that cutout. Current barrel is also a 7mm STW but the customer wants the same except slightly heavier barrel throated for 180's. Not real sure what tool to use other than perhaps ramping an endmill down on a mill after cutting the tenon and chambering. Any help on this would be greatly appreciated as always!

 

[Danny1788]

http://forum.accurateshooter.com/threads/win-m-70-extractor-cut-new-style-or-old.4002318/

 

[Dusty Stevens]

They make a cutter for it. Its dished in the middle to put the proper radius right at the chamber edge

 

[Walt Krafft]

Manson M70 extractor cutter

 

[INTJ]

A customer brought me a Winchester Model 70 Laredo to chamber in 7mm STW and this will be my first Winchester project and I'm in a bit of a quandary so time to ask the pros again. I broke the current barrel loose and it's got a cutout in the tenon threads for, what I assume to be, the extractor claw. However, I can't find much info on this and most of the Model 70 chambering/tenon info I see doesn't show that cutout. Current barrel is also a 7mm STW but the customer wants the same except slightly heavier barrel throated for 180's. Not real sure what tool to use other than perhaps ramping an endmill down on a mill after cutting the tenon and chambering. Any help on this would be greatly appreciated as always!

I did it the first time recently and it came out great. I am am not a machinist or a gunsmith.

It doesn't matter if you cut it flat or angled as Winchester has done it both ways. Here is how mine looked. This is in a "New" M-70 with 28 TPI tenon threads. I used the PTG cutter. I don't remember if I used my radiused on or my straight cutter.

 

[Danny1788]

Looks radius cut to me, I used the same cutter after the thread we posted in together. It turned out good, it was a pre64 action. Only ever did the one barrel.

 

[Kck]

Sorry gents, a little late on getting back. Tenon is the 1.000” X 16 threads. I need to do the homework on the angle of the BN recess as well as making sure the cutout is clocked dead on 90 degrees but it looks like the cutter made for this will be the way to go.

 

[INTJ]

Sorry gents, a little late on getting back. Tenon is the 1.000” X 16 threads. I need to do the homework on the angle of the BN recess as well as making sure the cutout is clocked dead on 90 degrees but it looks like the cutter made for this will be the way to go.

PTG and Manson both make 96 degree cone cutters. I guess if you are only going to do one you can use the compound. It will need to be at either 48 or 42, depending on how you measure.

 

[Keith Kilby]

To find 90 for extractor is easy. Torque barrel in after you're done with everything in the lathe. Witness mark so you can return to same point. Clamp barreled action in mill with bolt lug races level and horizontal. Use either a scope base or lug race to level. Clamp v block to barrel and square it to mill table. You can now unscrew barrel and have a 90 reference to mill extractor cut. I have done them with woodruff cutter but dedicated form tool is the way to go. I use same process when doing extractor cuts in falling block rifles with round barrels....like Ruger No.1 or Winchester 1885. Octagon barrels have built in reference for 90.

 

[INTJ]

I didn't have a good way to witness mark, but Prussian Blue on the extractor face worked well

 

[PWS]

I use a lathe tool blank in the lug race to mark the location on the cone once the barrel is torqued into position. The bottom mark is easy to make - just lay the bit in the lug race, move it forward to touch the cone and move it such that it leaves a scratch. Top side takes a bit of finesse since the race is so short at the receiver ring but it's not hard to hold the bit parallel while making the top witness mark.

Manson's extractor cutter leaves ample clearance for the height of the extractor so I just visually square up the barrel in the milling attachment with a 6" rule or the same tool blank to aligned with the scratches, bump the cutter on the outside of the threads, move in the sum of half the diameter of the tenon and thickness of the cutter and it's centered.

It's also possible to use a go gauge to judge how deep to make the cut. If you look at INTJ's center photo, the distance the case head is protruding beyond the chamber edge in the relief cut is what you're measuring. Most M70 extractors measure around .130 forward of the bolt face so the same (or slightly less due to the angle of the extractor hook) leaves plenty of clearance without exposing too much case head.