Curious Sino-Banian Barrel replacement. (1.5mil Foxtrot)

[Boris Badinov]

Someone posted a very nice, all matching 1.5mil on gunboards today.

https://www.gunboards.com/threads/1970-15-mil-factory-26-sks-uncommon.1206446/#post-
10889746
Never seen this type of barrel-receiver "RE-Indexing" before:
Barrel # is 25
Receiver # is 6

However, just to the right of the 6 is a very lightly etched 25.

Anyone ever seen this before?

[Boris Badinov]

I'm curious (i.e. confused) how such a mating would be possible as 6 and 25 would thread almost 180° apart......

If the barrel were installed upside down, would  this minimize the amount of re-tapping required for the receiver?  Or would that short-seat the barrel? (What am i even saying?)

[running-man]

Here's what I think.  Not 100% certain (and how can anyone be of any SKS?) but I think it's highly plausible:

This is what the clocking looks like on a protractor:


Note that the solid red line would be a perfect 180° opposite.  When LC did the physical testing to verify our hypothesis that these numbers are indeed barrel indexing number, he actually took two guns that were a perfect 180° opposite.  With the barrels off, he then installed one barrel on the opposite receiver, torqued it in place and it indeed was exactly 180° off.

In this case, it appears that they took a new barrel that was 10° more than 180° apart, and utilized it based on the dotted blue line.  My guess is that they may have shaved a few thousandths off the face of the receiver, taken some off the seating surface of the barrel, and/or torqued the hell out of it to get the two flats on the short barrel lug to clock properly.  If they did this, it would require the gas port to not have been pre-drilled (as it would be upside down), but instead to be drilled after the barrel was installed on the gun (which I think was probably standard practice, but I have no data backing this up at all.  With the accurate clocking method used they could easily have predrilled those ports).  The Yugo replacement barrels that Sarco had way back when were indeed undrilled for the gas port, so I think there is precedence for this.

It's definitely an interesting specimen.  I've seen non matching #'s before, but not from guns in this recent import batch.  One has to wonder whether it was a replacement barrel, or they simply utilized a new barrel that didn't quite index perfectly during initial production because they were running low on certain parts. 

[Greatguns]

The same guy posted on the 'other' boards asking for info on it stating he had found some info on the files and the SKSguide. I almost posted up that he wasn't going to get any good info on it from them, but I thought better of it. It did make me chuckle a bit though.

[Loose}{Cannon]

What RM said

One can easily change the index by removing material from the receiver face.