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Another homemade actions on the horizon

taiwanluthiers

Cast Iron
Joined
Dec 6, 2016
Location
Xinjhuan District, New Taipei City
Well, this time I think I can probably risk using Gary's broached blank rather than starting with a bar stock...

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So I got a long action, magnum bolt, Gary's blank, and a 300 win mag barrel. Blank is already broached so the bolt fits nicely. All that is needed is ream and thread the front, machine the back, the magazine well, the ejection port, cams, etc. and it should be shootable.

The only problem is, as of late I had very little free time. Calculus is kicking my butt and so is physics. I'm also doing research on the side so I haven't gotten a lot of time actually operating the machines. The only thing really giving me pause is trying to find the right orientation (making sure the raceway is exactly parallel with the machine table) so I can machine a flat onto the blank. However there really isn't a lot of material for me to do that. Not to mention I really don't want to make a mistake on a 250 dollar blank... those 4140 bars cost 12 dollars each so if I mess up all I lost is the time.
 
"ream and thread the front"? Ream what and why? The barrel is already threaded and you are trying to make the receiver fit it? Kind of backwards sounding.
 
Why does it need to be reamed? Clearly there is a hole there for the wire to cut the bolt lug slots. Now fixture based on those slots, bore it and thread it. No reaming involved that I can see unless it's after the boring op to improve finish behind the locking groove. That area would be purely cosmetic since the bolt travel would be on the lugs and cocking piece. A bored finish can rival a reamed finish, properly done.
 
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Barrel front bored. I made it a tiny bit larger than before, to make tapping easier because last time that area was too tight so it took a huge amount of effort to tap it. That gave me barrel alignment issues that had to be corrected.

I was really struggling with new/poor geometry boring bars, it wouldn't cut but would instead ride over the metal and making horrible sounds as well as lots of heat. I took one and meticulously ground it on a dremel diamond wheel. Factory geometry sucks and so it would dull within minutes of using it.
 
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I tapped the front portion and fitted a barrel to it. Fit is perfect, no wobbles or play (unlike the last one where the barrel sat at an angle to the receiver so I had to push the thread a bit, causing the fit to be very loose, thank God no kabooms when I fire it).

In other news, I had another 4140 bar stock "gun drilled". The worst thing about the G0704 is the fact that the quill travel is short (only 2 inches) so I had to be really creative when drilling deep holes. Basically the flutes would get loaded up with shavings and would bind in the hole. So I have to stop the drill, raise the head, and clear the hole, and repeat. It made for very slow progress. Hopefully the progress will be a lot faster now since I got a through hole meaning space for shavings to fall through. I really need to fit a power lift on the head because right now lifting the head is a real workout manually.
 
Bolt fitted. Both chambering and extraction cam machined. It wasn't easy but I used a dremel for the chambering cam inside the receiver, then used a cutoff disk on the bolt lug itself and put a really small chamfering (as small as I can so I don't cause structural integrity problems) to complete that part of the cam. Then I worked on the extraction cam, which meant I had to machine the back part really carefully. It took several hours and setting up the mill several times to make that 30 degree angle cut (I used a protractor to set that angle.. I know this is not a school project but they are accurate enough)

Bolt now chambers and extracts very smoothly.

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Before you wonder where the ejection port is, until they can extract and chamber smoothly they do not deserve an ejection port. That will come up next.
 








 
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