Soviet Re-arsenal re-barreling?

[Loose}{Cannon]

Before.

Otherwise you run the risk of cutting into the receiver face ultimately shortening it, and we would find different measurements from flat to flat especially on other nations.  Ironically they are all an exact MM wrench size.... Dont recall what that size is though. 

[Loose}{Cannon]

I guess that extractor recess was cut when installed also?   

You screw in a barrel with no flats and let it bottom out wherever it wants and cut the flats after.... You also cutting the extractor recess after...

[Justin Hell]

 

I will never again **** about the removal of a FSB. 

Jebus, I had no idea.

I can see why you aren't cranking the straight pull match grade SKSs out left and right.  How much trial and error was involved in mating a barrel to your receiver?

[Loose}{Cannon]

Laff Justin...  I just like keeping ole Boris on his heels and toes. 

Xtriggerman sent me two steel half circle deals with the same diameter of the barrel to protect it when clamping in the vice and I put a large crescent wrench on the receiver.

I locked it down and plotted where the extractor recess would be, took it out and cut it, torqued it back on the receiver.

[Boris Badinov]

Before.

Otherwise you run the risk of cutting into the receiver face ultimately shortening it, and we would find different measurements from flat to flat especially on other nations.  Ironically they are all an exact MM wrench size.... Dont recall what that size is though.

I guess that extractor recess was cut when installed also?   

You screw in a barrel with no flats and let it bottom out wherever it wants and cut the flats after.... You also cutting the extractor recess after...

Again. Which? Cut the lug flats before or after? From the above statements it sounds like you are saying both.


I wlll get the rifles out later tonight (hopefully) and report what I find. Where are the numbers located on the crossbolts?

We had an unexpected visit from non-firearm-friendly guests in town for Thanksgiving.

[Loose}{Cannon]

It was a statement...  That if you cut flats on lug while installed, your also cutting the extractor recess installed? 

I have never seen deeper mill cuts on the upper and lower of the receiver face... You would think an offset step would be seen from the side if even ONE was cut further then flush by even a few thousands. 

I ask again.   "If" these numbers are not rated to barrel index sizing etc, what are they for?  I don't believe the off/on story because in the factory you would need alot more numbers then 36.... Like a serial number. In addition, iffin your taking off a barrel to replace it..... WTH would you care about a number on it.  Its being scrapped!  Literally make no sense.

[Boris Badinov]

It was a statement...  That if you cut flats on lug while installed, your also cutting the extractor recess installed? 
I ask again.   "If" these numbers are not rated to barrel index sizing etc, what are they for?  I don't believe the off/on story because in the factory you would need alot more numbers then 36.... Like a serial number. In addition,

This is what I am referring to regarding definitive claims regarding a process none of us were there to witness. At 250k guns per year,  that's a 685 guns per day average. Why would paired number sets of 1-36 be insufficient? This would require only 19 people. Or 8.5 people performing the same task  twice for two batches of numerically paired barrels and receivers stamped 1-36.

It's a bold claim that implies an intimate knowledge of the actual production processes employed by the soviets, and the number of people employed by the arsenal performing one specific task within the order of assembly.

In addition, iffin your taking off a barrel to replace it..... WTH would you care about a number on it.  Its being scrapped!  Literally make no sense.

As I've stated already, I am doubtful about the frequency and practicality of replacing barrels during refurb.  I thought I was clear earlier and elsewhere that I believe these numbers are related to assembly not dismantling and replacement.

....

Also: I'm still not clear on what you mean exactly when you refer to barrel "indexing" and head spacing.

Are you referring to aligning the curvature of the barrel bore to the vertical axis of the rifle to improve accuracy?

Or...

Are you referring to the process of incrementally indexing the barrel to seat it within the receiver with the proper head space?

[Boris Badinov]

If these numbers have anything to do with indexing a threaded barrel and nothing to do with keeping them together with the receiver. Then pinned barrels will NOT have them.

Dude, my entire POV is that the numbered pairs ARE index specific. I just disagree that they refer to specific measurement. My whole argument is that the paired numbers are stamped so that the indexed pair (barrel and receiver) are reunited after being separated.

Whether they are separated after initial indexing is where I think our disagreement is.

So.. Why would they be separated after indexing? :

To ream the chamber and machine the receiver face. And finally to machine the lug flats before re-installing into the receiver.


....


I do not own any pinned-barrel guns. But, my guess is that they do not have paired barrel receiver numbers.

[running-man]

This is a great thread.  Really getting us to think through different scenarios and contemplate the likely from the possibly all the way to the the ludicrous. 

We can all step back take a nice deep breath, we're all adults here and there's no need for anyone to take anything said here personally (not that that's happened or would happen, but I'm just trying head off any possible disaster that might be around the corner...I really like this thread!!)   We will possibly never know the answer, as Boris says nobody was there when these were refurbed and we can't determine things in absolutes.  We can perhaps determine more likely vs more unlikely with a bit more data though.  LC's idea of looking at pinned barrels is a good one.  We have to make certain that we don't take data from formerly threaded receivers that were subsequently scrubbed (perhaps not all the way) and converted into pinned barreled receivers.  Also, we have to realize that the Chinese and Russians, while they started out in 1956 with approximately the same hardware with very similar stampings, really did have different assembly and refurb setups by the time the pinned barrels rolled around in the ~1970 timeframe. 

So LC's comments on the barrel indexing is interesting.  I had totally forgotten about the relief cut for the extractor.  That's a game changer right there in my opinion, made the little light bulb go on in my head! 

So you're not just trying to get one of two flats to the horizontal position when you put a barrel and a receiver together.  That's hard enough with many different variations on flat position vs. thread start location.  Now that you are trying to clock the extractor relief cut to an exact location, you have quite a few possibilities - 360 of them if you cared about every single degree.  Maybe you don't care about every degree though, maybe if you're within 10°, you can make the barrel clock correctly either through additional torque, peening the faces, other tricks we might not even know about etc.  So 360°/10° = 36. 

Additionally, you start at 0° and never get to 360° because 360° = 0° when clocking something.


 
So 36 units, starting at 0, going to 35 indicating the clocking orientation of the extractor (and by default the flats, flats are always located the same with respect to the extractor on every barrel regardless of anything else) compared to the starting point on the threads.  Sound familiar?  

I'm thinking this is what these numbers truly mean.  Not assembly numbers indicating 1 out of 36 units, but the clocking angle of the extractor as it is mated to the receiver.  What do you guys think?!

[Loose}{Cannon]

They stamp them for future armorers

rebarreling would seem to be one procedure that would definitely require a stamp of some sort.

the top and bottom lug flats must be machined after the barrel has been fully seated into the receiver

And the mother of all contradictions within the same post. 

This would require only 19 people. Or 8.5 people performing the same task  twice for two batches of numerically paired barrels and receivers stamped 1-36.

It's a bold claim that implies an intimate knowledge of the actual production processes employed by the soviets,

Their called opinions Boris.... Opinions.  You have them, and so do I.

Its a bit frustrating and monotonous explaining the same thing over and over and people out right fail to comprehend what your slapping down or blantantly misrepresent what you are saying.

Lets chop up this lastest one for craps and giggle and go from there.

So.. Why would they be separated after indexing? :

To ream the chamber and machine the receiver face. And finally to machine the lug flats before re-installing into the receiver.

The chamber has already been reamed. How do I know?  Because 36 numbers wouldn't keep hundreds if not thousands of barrels matched to receivers when they are separated for CHROMING..... You would need a much larger number and a bunch of monkeys trying to put the puzzle back together at a later date.

The receiver face....   You take off .001 off that face and your barrel will insert even further into the receiver and you will index an untold number of rotational degrees PAST your index.  What comes next?  You would then have to machine MORE off the face until you come back around another 300 someodd damn degrees before indexing again.  Now what?  Welp, now the chamber face insertion depth into the receiver is too deep.  What will that cause?  For starters, now your taking off THAT much more off the back of the bolt to headspace.  Anything else?  Yes, now when the RSB is seated flush to the receiver, it also has now moved back which means your magazine mounting tab on the bottom of the RSB will push the mag too far rearward and will not clear the mid receiver tang AND you may have feeding issues. 

Machining the lug flats.  Welp....  Just how would you know exactly where said flats need to be?


My opinion is simple. 

#1.  Throwing out the most valuable and tedious component and heart of the rifle because a barrel is bad..... Rediculous

#2.  Barrels and receivers milling processes were complete prior to mating and they used a simple numbering system to ensure proper indexing every time without adding all kinds of time consuming additional individualized procedures and throwing repeatability out the window along with consistency and any hope for interchangeability of numerous components. 

[Loose}{Cannon]

So 36 units, starting at 0, going to 35

Ever seen 0 stamped?   I would venture to say 1 through 36 with no 0.   

Otherwise, I love the idea.  In fact GM just sent the notion to me a bit ago and I told him its outstanding. 

There HAS to be a control for this procedure..... My opinion.

[running-man]

So 36 units, starting at 0, going to 35

Ever seen 0 stamped?   I would venture to say 1 through 36 with no 0.   

Otherwise, I love the idea.  In fact GM just sent the notion to me a bit ago and I told him its outstanding. 

There HAS to be a control for this procedure..... My opinion.

Yup, there are absolutely 0-35.  The 0's always bothered me....why not start at 1 I always thought.  i think what I've mentioned explains it pretty well.

Never seen a 36 in my 17 years of collecting and believe me I've been looking for one higher than 35......

[Loose}{Cannon]

Ah... Ok.   I just remembered you stating 36 total numbers and didn't realize it was 0-35 and not 1-36.   

[Boris Badinov]

Ahh. So...1-36 are the only numbers  known to have been stamped in pairs on the left side receiver and barrel flats?


Also, machining the lug flats with the barrel separated from the receiver  AFTER indexing = not impossible. The top and bottom lug flats don't have to be perfectly perpendicular to the barrel axis, they only need to be parallel to one another.

Hypothetically, the lug flats could have been machined according to witness marks that were stamped once the barrel and receiver had been fully indexed and seated. We wouldn't be able to see these witness marks  because they were removed when the lug flats were machined.
-----------


What RM has illustrated and explained above -- notably with nary an ounce nor one square inch of condescension -- seems entirely plausible IF 1-36 are the limit on stamped pairs. Numbers larger than 36 would make the explanation less likely.

If true, however, it still leaves unexplained the existence of the barrel/receiver alignment hash marks. Which leaves open the possibility that barrelled receivers were separated during assembly and after initial indexing and seating. If 10° is the margin of error for re-seating the barrel, then the hash mark would be an easy reference for RE-attaching a barrel that has been removed from the receiver during initial assembly. Get the hash marks close enough and yer extractor clearance and head space are good to go.

...and  from this, one possible indication of a replacement barrel could be the absence of the hash mark on the barrel lug. No?


Correction: 0-35 not 1-36.

[Loose}{Cannon]

No.     

Remember, RM isn't dealing with shots across his bow so expect his response to be more....  Peaceful? 

If the numbers represent what RM describes, then.....

#1.  I am right in that they are an indexing control number based off of measurements to ensure proper indexing..... Everytime, and without causing further serious complications. 

#2.   They are not to keep barrels and receivers together while the factory monkeys "screw" with them all day. Pun intended. 

[Boris Badinov]

So... likely many "as-issued" "all original" "matching"  guns out there have replacement barrels?

Also, still no exlpanation for the alignment wintess mark/hash mark?

And no means of detecting a replacement barrel?

[running-man]

I would think the indexing mark on both the barrel and receiver were stamped prior to installing the barrel on the receiver.  If you have a jig, you can make that mark in the same spot on both pieces each and every time.  I don't remember seeing much variation in the indexing marks..maybe in total length, but as far as position, they are always 90° to the surface of the receiver where the S/N lies.  Marking both prior to installation would mean that the Russian tech assembling things would have to grab a barrel and a receiver, then figure out a way to get the two lines to line up with each other.  At that point, the extractor cut and flats would both be exactly where they needed to be.  Headspacing would still need checked and possibly tweaked, but that could be done via other parts such as the bolt itself or even the hardened square key that the rear angle of the bolt locks into...

[Loose}{Cannon]

You clock where thread starts, mark the degree, match up the numbers.  Its that simple.   

[Loose}{Cannon]

Hold your fire Boris....  Ill let RM explain the procedure in better detail, but for now.

Its nearly impossible to clock the starting position of male or female threads even on the most modern CNC machines yet alone in the 50s.

What your looking at is rotational degrees that are plotted prior to mating of the components.  You would mark the witness mark 90° from 12 o'clock and thread the barrel into a jig. This jig would have 360° marks all the way around it in 10° increments from 0 to 35.  When you seat the barrel all the way into the threaded jig your witness mark will land on a number.  You stamp that number which literally plots the beginning location of the first thread.  You do the same on the receiver using a male jig and stamp the number. 

You have receivers and barrels on standby numbered 0 through 35 representing the rotational angle of the begging thread.  You achieve perfect index every time you match the numbers. 

It explains the witness marks, the numbers, and the entire process of how they indexed barrels to receivers.

Case closed.

[running-man]

Yeah, machining threads consistently from part to part in the 50's would have been a nightmare.  Even today, if someone wants a precise start point on a part they would tend to threadmill it by driving the helix instead of trying to single point it out on an NC lathe. 

So you know something I just thought of (LC probably already assumed this but it wasn't apparent to me until I thought about it for a bit), if the numbers are indeed representing 360°/10°, then it would make sense that if a barrel was changed...the numbers would never be different.  If a #15 barrel/receiver combo was shot out and the Russians chose to rebarrel that firearm, they would replace the old #15 barrel with a new #15 barrel.  You wouldn't be able to tell at all by looking at that number.   

Yup, I do like this thread a great deal!