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Military Firearm Restoration Corner

Odd Greater Thread Diameter On A '38 Swede Barrel


BobVZ

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I'm considering buying a NOS Swede M38 replacement military barrel for a "Twede" project. When measuring the greater diameter shank thread I'm getting .992 in. rather than the stated .980 for this barrel. I've taken 4 measurements around the circumference at 90 degree intervals and the measure is consistent. My caliper is correct and accurately measures some M98 barrels I have at 1.10 in. Is this normal for these barrels? Will I likely run into fitting problems mating it to a Turk receiver? Whats been your experience?

 

Thanks,

 

Bob

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Does the barrel actually fit in the receiver?

 

Most folks visualize barrel threads as true, sharp "Vs". They aren't; they have flats (or rounds) both in the root and on the crest.

 

The actual thread engagement between the receiver threads and barrel shank threads occurs on the angled part of the thread, or the 60 degree part.

 

A barrel's threads could be considerably under the spec major diameter or SLIGHTLY over (provided they don't "bottom-out" on the flat (or rounded) receiver root. The actual plunge depth for either scenario should be the same.

 

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Does the barrel actually fit in the receiver?

 

Most folks visualize barrel threads as true, sharp "Vs". They aren't; they have flats (or rounds) both in the root and on the crest.

 

The actual thread engagement between the receiver threads and barrel shank threads occurs on the angled part of the thread, or the 60 degree part.

 

A barrel's threads could be considerably under the spec major diameter or SLIGHTLY over (provided they don't "bottom-out" on the flat (or rounded) receiver root. The actual plunge depth for either scenario should be the same.

If its a left hand thread it may be a 6.5 barrel for a norwegian krag. If so lets make a deal!!! Jim

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I've got several swede barrel sthat are not consistent on thread size. It happens. Chase them until you get a good fit. One I have right now is a 9.3x57 bbl of a LR Husky sporter that mics 1.110". Another off a Husky 1640 mics .990 yet, another 1640 I recently did measures .980". So much for that Swede precision. It happes, swedes aren't the only rifles so afflicted. That's why it is a good idea to ALWAYS measure.

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Z1r,

 

Would you recommend the Brownells chasing die/tap sets? I'm concerned about whether they are 55 degree or 60 degree. I'd rather leave the Swede and the Turk in 55 degree, but if I use both then I guess they would be matched. Is the chasing die capable of removing that much metal? I noticed in the catalog pic the die has and adjustment screw that would let me open it up a bit. Does this mean I could make several passes and gradually work down the die?

 

Thanks,

 

Bob

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Bob, I haven't checked my latest Brownells cat, but I thought those Mauser taps and dies were kinda pricey. For that kind of money and depending on where your located, Z could put that barrel in his lathe, pick up the existing thread and fit the recvr to it. You'll have a better thread than a tap/die fit. Someones gonna have to put that barrel in a lathe eventually to set the head space, no?

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Z1r,

 

Would you recommend the Brownells chasing die/tap sets? I'm concerned about whether they are 55 degree or 60 degree. I'd rather leave the Swede and the Turk in 55 degree, but if I use both then I guess they would be matched. Is the chasing die capable of removing that much metal? I noticed in the catalog pic the die has and adjustment screw that would let me open it up a bit. Does this mean I could make several passes and gradually work down the die?

 

Thanks,

 

Bob

 

Bob, those taps were made to prep the receiver for short chambered barrels which use 60 degree threads. In theory you could use both but I'm pretty sure the tap & die will set you back better than $100. You could also run into the problem of the die bottoming out due to the shank being too large in diameter.

 

Like I said, on my 9.3x57 bbl I will be chasing the thread just like Walnut said. There is a good chane that you will need to setback one or both shoulders to get the barrel to fit. Headspace may or may not be correct. I have a new swede barrel and there is no way it will screw into my K.Kale receiver and headspace correctly without seing the lathe first. the shank on this barrel is too long. I have another 6.5 barrel in the from a customer's gun and it's shank would be too short. You might get lucky though.

 

 

 

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