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 Barrel replacement

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jnestor



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PostSubject: Barrel replacement   Sat Jan 19, 2013 9:11 pm

Hi everybody,

Michael here. I did not post here yet, but I've been lurking around for quite some time. Now, here is my story.

My original barrel, while having visually good bore, slugs to .318 - and shoots accordingly. At some point I went ahead and bought another barrel in excellent shape, that slugs to .314. BUT. This barrel does not index. Not having access to lathe, I decided it must be cheaper to try and buy a barrel that does index, than to hire a gunsmith to index the one I have.

I am assuming buying a barrel that comes from the same receiver type, has been made the same year and on the same plant as the original one - will increase my chances to get it indexed without gunsmith intervention.

So, the question is - does my line of thinking have any merit or am I just completely off? And if it does - does anybody have a barrel to sell that matches my requirements? I am looking for 29" Tula barrel made around 1927, with excellent bore.

Thank you.
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SilverTip
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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 1:18 am

Hey! Welcome aboard. You have a 27' barrel that specs out to .318!? pale Holy cow thats alot. In my limited experience, the older of mosins I look at, the tighter the bores are. And ive never seen one over .314 (with rifling left). Thats wild.

Anyways, thats an excellent question, that ive pondered myself a time or two.

First, lets look at where your at with your .314 replacement barrel. We may be able to get you going with it.

First some questions.

Do you have a head space gauge?
When you say the barrel does not index, are you referring to the extractor cut?
The original extractor cut should be between (approx) 1oclock and 5oclock. Where does yours end up?

I have bought several barrels over the years, and have also noticed theres no rhyme or reason to the indexing of their features.

I dont know the specifics of the manuf process of these barrels. At first, it seems to make sense to look for what you are saying. Matching the barrel manuf date and plant with the receiver. But givin the variations ive seen when assembling various barrels and receivers, i'd say thats not likely to be the case. But please get a second and third opinion on that.
It may well prove true that during short periods, the machines, operators, and material maintained enough consistency to do what you are asking.
But I think the biggest concern is looking for that specific dated barrel. You may look for a week, or 10yrs for that puppy. [You must be registered and logged in to see this image.]

I have some ideas that we can narrow your barrel search down with, if you think thats the route to go.
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Zeiss Ikon



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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 1:28 pm

These barrels were made before CNC, and the extractor cuts were done after they were off the lathe from threading; there is literally no correspondence between the thread start and the rotation-critical features like extractor cut. Buy another barrel, and you'll get another random orientation. The only way to get the extractor cut to align is to either shim (copper crush washer between barrel shoulder and receiver) or turn off the shoulder until the barrel clocks correctly -- and shimming will increase headspace (probably beyond field gage, i.e. to unsafe dimensions), while setting back will require cleaning up the chamber with a correct chamber reamer to restore headspace, if you have to take off more than a few thousandths. This really is a job for a gunsmith or an amateur with the correct tools and either experience or the money to buy multiple barrels to learn on.
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SilverTip
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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 3:11 pm

Thanks for that machining info Zeiss. [You must be registered and logged in to see this image.]

The extractor groove can be done with a dremel by a steady hand. This is the easiest modification in relation to everything Zeiss just said. That is why my number 1 goal when installing a barrel is correct headspace, and everything else there after (extractor indexing) is taken care of as needed. Much less work.
But, the down side to that route is your sights will likely be off.
Since I only use scopes, im not concerned with open sights.

The best I can think of doing would be, look at your barrel and make note of where your threads start in relation to your extractor groove. Match that placement up with replacement barrels. Problem there is, you will need to visually inspect MANY barrels. And thats still no guarantee that the breech face to barrel shoulder distance is correct on the barrels.... unless you also measure that from the original.

On a side note, You may find it much easier to buy one with a tighter bore.
I just looked at 5 Chinese M44's (type 53's) yesterday. I had never ran across these and have always wanted to see how well they were made (since that is what seems to be the most prevalent M44 on the market now). I was very impressed. The machining on them was MUCH nicer than the russian war time mosins. Much fewer machining marks. The bolts cycled much smoother with less chatter/play. And the bores were pretty shiny. Shinier than 90% of all mosins ive looked at in the past.
I will be getting me one for sure. That may be much easier for you to do. ?
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jnestor



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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 6:47 pm

Hi folks, and thank you for the welcome Smile

Yes, it is 27' with strong rifling (though not sharp) - and it slugs to .318.

Yes, I do have a No-Go headspace gage.

Barrel stops about half a turn before the proper position, hand tightened. And about quarter of a turn - tightened with serious torque (I did not measure it, but with my weight of more than 200 lbs and receiver wrench handle about 1 foot it gives right about 200 ft*lb).

Obviously, the extractor cut is off about half a turn hand tightened, too. But as you rightly noticed, the extractor groove is the least concern. Site bases are off the same amount, of course. Head space will be the same if the shoulder to the end size of old and new barrels are the same - and they actually are almost equal, within a couple of thousands.

Zeiss, you got me puzzled a bit with your description of the process. If we assume the start was completely random, how did they cut the rear site base dovetail? It looks like made together with the rest of the barrel, in a single piece? And did receivers have a random thread start, too?

SilverTip, I have a better method of testing the fit. I hand tightened the receiver stub to the original barrel, and marked the middle of the site bases line on the stub. Now, whatever other barrel I screw it on, I see exactly how much off it is.

So, if barrels seller is willing to make this simple test for me, I can ship the stub before buying and he can pick the barrel that fits. This is the idea Smile
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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 7:26 pm

Sounds like you got a pretty solid grasp of it. Smile I hope you can get it going.

jnestor wrote:

SilverTip, I have a better method of testing the fit. I hand tightened the receiver stub to the original barrel, and marked the middle of the site bases line on the stub. Now, whatever other barrel I screw it on, I see exactly how much off it is.

So, if barrels seller is willing to make this simple test for me, I can ship the stub before buying and he can pick the barrel that fits. This is the idea Smile


Unless im misunderstanding your idea, the receiver is whats considered the 'firearm' and therefore is subject to specific shipping requirements. You can only ship to a licensed person.
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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 8:03 pm

I have a barrel laying here I can measure if you have the specifics. Its a 1938 Izzy.
Decent rifling. Slugs to .3135-.314.

Also, you might be able to get this guy to sort through his barrels. [You must be registered and logged in to see this link.]
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jnestor



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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 8:14 pm

SilverTip wrote:
Unless im misunderstanding your idea, the receiver is whats considered the 'firearm' and therefore is subject to specific shipping requirements. You can only ship to a licensed person.

Not the whole receiver, just receiver stub. Many sellers just cut out the big chunk of the receiver, and sell barrels with stubs - to avoid unscrewing barrel hassle. So, the one I bought came with the stub, and I can use this stub now. This piece of metal one can ship freely.
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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 8:40 pm

Oh, a cut receiver. I understand. Smile
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Zeiss Ikon



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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 9:44 pm

jnestor wrote:
Zeiss, you got me puzzled a bit with your description of the process. If we assume the start was completely random, how did they cut the rear site base dovetail? It looks like made together with the rest of the barrel, in a single piece? And did receivers have a random thread start, too?

The rear sight dovetail was most likely cut after the barrel was assembled to the receiver and both were numbered, but before the barrel was profiled; the barrel was then removed and turned to profile, leaving a large collar where the sight mount was to be, which was then cut to shape and the extra metal removed to finish the profile by either a shaper or a milling machine (most likely a mill; this would be a difficult setup for a shaper). If you look closely, you'll see the tool marks on the barrel are different at the dovetail and for a short distance to either end. The front sight mount for a 91/30 or older version would have been cut the same way; the M38 and M44 seem to have sleeved on front sights, but I could be wrong on that (never handled those models).

All this means that the sight mounts and extractor relief were both cut to fit on match-numbered barrel and receiver after they'd been mated to mark position. Yes, the receiver threads have a random start, too, most likely -- it was technically possible to start threads at one point on either part (chuck by shape and at a precise protrusion, so the thread cutter would touch metal at a specific clock position), but the positioning required to do that on a manual lathe would have taken up time on the profiling and threading lathes, where machining the sight mounts after mating and marking could be done on a different machine, and production rate with limited production resources was paramount for post-1939 units. If one part was random threaded, moreover, it would make no sense to precision start the thread on the other part, and precision starting the barrel would be significantly more difficult than precision starting the receiver.

Bottom line, for a mass produced infantry rifle made in the numbers the Mosin Nagant was, in wartime production, there was nothing to be gained by making barrels interchangeable on receivers -- match numbering made this unnecessary.

Now, if you were fitting a new barrel to an existing receiver (as was occasionally done at arsenals when refurbishing), you'd cut back the barrel shoulder until the sights aligned correctly, reface the chamber end, recut the chamber, and then recut the extractor relief -- then number the new barrel to match the old receiver.
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jnestor



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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 10:56 pm

SilverTip wrote:
I have a barrel laying here I can measure if you have the specifics. Its a 1938 Izzy.
Decent rifling. Slugs to .3135-.314.

Also, you might be able to get this guy to sort through his barrels. [You must be registered and logged in to see this link.]
Thank you SilverTip. I may take you on your offer later. Right now I have a gentleman whom I likely be sending this stub for test on his three finnish barrels. BTW, sending the stub was his idea, not mine. If this does not work for his barrels, I'll contact you, OK?
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jnestor



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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 11:06 pm

Zeiss Ikon wrote:
Now, if you were fitting a new barrel to an existing receiver (as was occasionally done at arsenals when refurbishing), you'd cut back the barrel shoulder until the sights aligned correctly, reface the chamber end, recut the chamber, and then recut the extractor relief -- then number the new barrel to match the old receiver.
If i was an arsenal, I would certainly go this route LOL. Since I lack equipment and skills, I am trying to find other ways. Smile

Thank you for your explanation, it certainly makes sense. Funny thing though, since I asked you this questions, I made some searches on the internet and found the old Russian book titled "Manufacturing of barrels". It was published in 1945 by Soviet military academy - which was and still is the most authoritative military university in Russia. If you know Russian and have an interest, I can send the pdf to you. So, this book specifically states on page 6: "thread on 91/30 rifle barrel is cut after finishing of the protrusions, so they can be used as a base". This sort of negates your reasoning, I think.
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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 11:32 pm

jnestor wrote:
I made some searches on the internet and found the old Russian book titled "Manufacturing of barrels". It was published in 1945 by Soviet military academy - which was and still is the most authoritative military university in Russia. If you know Russian and have an interest, I can send the pdf to you. So, this book specifically states on page 6: "thread on 91/30 rifle barrel is cut after finishing of the protrusions, so they can be used as a base".

Excellent.... [You must be registered and logged in to see this image.] me want
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jnestor



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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 11:46 pm

SilverTip wrote:
jnestor wrote:
I made some searches on the internet and found the old Russian book titled "Manufacturing of barrels". It was published in 1945 by Soviet military academy - which was and still is the most authoritative military university in Russia. If you know Russian and have an interest, I can send the pdf to you. So, this book specifically states on page 6: "thread on 91/30 rifle barrel is cut after finishing of the protrusions, so they can be used as a base".

Excellent.... [You must be registered and logged in to see this image.] me want
Umm, tried to attach the pdf to the post, but it does not seem to work for me Sad
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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 11:55 pm

Ya. Just post a link.
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jnestor



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PostSubject: Re: Barrel replacement   Sun Jan 20, 2013 11:58 pm

[You must be registered and logged in to see this link.]
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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 12:25 am

Thanks! Im posting it to my mediafire account. And gonna work on translating and posting here in the forum.
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jnestor



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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 12:39 am

You are welcome Smile

BTW, I also found a repair manual published in 1950, though it is a djvu file. Interested?
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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 12:46 am

Yup. Thanks.
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jnestor



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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 12:50 am

Sure, here it is: [You must be registered and logged in to see this link.]
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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 12:51 am

I may have to pull that link down. My firefox is all dicked up now after downloading that first book. Are you having any issues?

Well, i guess I should consider, i also downloaded a translator. That might be it also.
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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 12:59 am

I had a weird popup after downloading djvu viewer. But it's fine for more than an hour now. Books themselves seem to be OK.
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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 1:01 am

Ya. Looks like it was one particular translator. Was a browser hijacker. It changed some default browsing settings and would open a new browser and redirect to the last page I opened.
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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 1:09 am

Heres a safer way to download the book. "Manufacturing of barrels" [You must be registered and logged in to see this link.]

Now just gotta figure out how to translate it. [You must be registered and logged in to see this image.]
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jnestor



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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 1:20 am

Cool, just remove the other one then, just in case.

And good luck with translation - though I would say more than 90% of the book is not about Mosin. It really is a general production guide, with a lot of info folks will never need. The second book is much more interesting for Mosin owners - but impossible to auto-translate because it is not OCRed...
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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 1:32 pm

Hmm. Shaping/milling the sight bases prior to cutting threads would have value only for either starting the threads at a particular clock location (much easier, if that's critical, to cut back the shoulder after threading, though that would change barrel length by up to one thread pitch unit -- 16 TPI for the barrel thread, as I recall), or to put the high-reject operation (cutting the dovetail and barrel taper for the rear sight base) before the low-reject one (threading the barrel for the receiver). I'd guess they did it for the latter reason; it's still faster to cut random threads and cut back the shoulder as needed than to precision start both barrel and receiver.
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PostSubject: Re: Barrel replacement   Mon Jan 21, 2013 10:34 pm

Well, yeah, does not sound like the most efficient approach at the first glance - but then they had all the data that we don't have, so may be it was the optimal way for them, then and there, all things considered. We never know unless we talk to somebody who was in charge, and these people are mostly dead already...

However, since they did precision starts (can't believe I found a proof of this LOL), looks like my approach may have some merit after all. Because these starting points do not have to be uniform across the arsenals and dates, but have to be uniform for the same plant over a certain date span. I wish I knew what that date span was. Smile
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PostSubject: Re: Barrel replacement   Tue Jan 22, 2013 1:13 am

I'll pm you a number to call Jnestor.
He's been to the factories. He may know something.

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