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Military Firearm Restoration Corner

Tap Size For An A&b Barrel


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I would like to know what tap size do I need for the A&B barrel to recut the the treads in the receiver of an mauser? If you can provide me with an part number and where to get it at, that would be even better.

 

Thanks in advance.

Rob

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Don't know if this helps, but I got lr and sr taps and dies. they are thread chasers. I got them from midway. have'nt check if they still sell them or not. they work just fine on my a&b barrels and mauser actions. Just my .035 worth. Dave

 

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I have an interesting situation. I have been using my lathe for a while now, but I have just started to learn to turn external threads. I plan to buy on of the pre-threaded short chambered barrels (probably Shilen) because I don't yet feel comfortable enough to thread an expensive blank. What I had planned to do is make some of the tooling to both offset cost and to hone my lathe skills. My first project is going to be a receiver mandrel. I know about the difference in the American barrels with 60 degree threads vs the European receivers with 55 degree threads. My thinking is since the barrel I'm looking to buy has 60 degree thread pitch then the mandrel threads should as well. So I know the receiver will not screw onto the mandrel easily because of the difference in threads. My question is should I lap the mandrel and receiver together? If I do lap them, what affect will it have on the barrel to receiver union later?

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Why don't you start by practicing some more, then make the proper mandrel, and if it turns out ok, thread a blank. Don't rush to get things done fast. Slow down, and learn to do them right. Why make a 60 degree mandrel when eventually you'll be cutting proper 55 degree threads? besides, you save lot's of money buying blanks instead of pre-threaded bbls.

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Why don't you start by practicing some more, then make the proper mandrel, and if it turns out ok, thread a blank. Don't rush to get things done fast. Slow down, and earn to do them right.

 

I agree completely Z that is the correct way to do it, and I may well go that route, but turning threads on an expennsive blank still scares the hell outta me. Let me ask the question this way. If one was to buy a mandrel from Brownells or Midway...would they not be in the same situation as I mentioned before? From what I've read the commercial mandrels also run 60 degree threads. Would lapping a commercial mandrel to an action have any adverse affect on the later union of a pre-threaded barrel to the action? I for one wouldn't want to drop 70 bucks on a tap.

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I agree completely Z that is the correct way to do it, and I may well go that route, but turning threads on an expennsive blank still scares the hell outta me. Let me ask the question this way. If one was to buy a mandrel from Brownells or Midway...would they not be in the same situation as I mentioned before? From what I've read the commercial mandrels also run 60 degree threads. Would lapping a commercial mandrel to an action have any adverse affect on the later union of a pre-threaded barrel to the action?

 

The answer is yes. What you will have done by lapping is changed the geometry on both the mandrel and the receievr threads. They won't be proper 60 or 55's. Get a couple of pieces of 1.125" bar stock and practice. That's how we started in both machine 101 and gunsmithing school. Making the tools is good practice. First thing we made in machining class was a tap holder. Learned to cut threads, angles, drill, ream, and read blueprints all on one tool.

 

If you planned to lap a prethreaded barrel to a receiver and then mount that barrel, that would be better.

 

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