After stripping a number of parts over the last few weeks, including several gas tubes...I made a bit of an epiphany regarding the finned barrels found on some Chinese SKSs.
If you have ever tried to get a gas tube into the white, you probably found yourself wondering why they made it such a pain in the neck with all those ribs under the handguard being so difficult to remove the bluing/paint, what have you. This feature of all SKSs doesn't get discussed, and is just considered the way it is I guess...but it serves a purpose. Cooling.
By ribbing the surface, you are increasing the surface area of the part in question. The gas tube is obviously getting some pert dern volcanic activity going on in there...especially under continued fire, the handguard is actually INSULATING it on more than half of it's surface, so the ribbing helps to combat that.
The ribbed barrels caused some to speculate that it was worn machinery putting a nick in the surface while it was being machined, but that would be more of a threading effect whereas the ribbed barrels exhibit more of an intent for them to be there...as they are circles, not spirals. They are combed into the surface after the barrel tapering has been completed. They are also not present in the locations where the RSB, stock ferrule, gas block and FSB are. Towards the front of the barrel taper, it seems like the combing for the ribs doesn't make contact, at least on some, my DB looks crummy in that area, whereas my 0226 it is perfectly machined...with intent. If the dating system is correct, and it it tough in this area to be sure, the DB should predate the 0226 by a couple of years....showing possible increased efficiency in doing it properly over time.
I think the Chinese were looking for a way to cool the barrels faster, perhaps to prolong life, perhaps to improve consistent accuracy...maybe just to reduce burnt hands? I want to get one of those laser temperature gauges, run two SKSs one regular, and one with the radiator barrel (I am trying to coin that...ribbed sounds too much like it is for her pleasure, and we already have French Ticklers) run ten rounds apiece through them, and note barrel temps over time, and see if it is both a viable hypothesis, and if it actually works.
It is a little sloppy out here still to try this out, but if anyone else has one of those gauges, both types of barrel and the willingness to burn through a box of ammo for the experiment...I am very curious if I am correct. Surface area, no mater tiny these fins are, is crucial for cooling...even a tiny amount on the surface is huge. Processors wouldn't need fans if they were given enough surface area on a heat sink to cool them, but computers would be much larger if that was how they did it. If you consider the valleys and peaks over the length of the barrel, with the ribs it gives the surface area of nearly two barrels.
After reading an article posted here (I forget by who and where) about the Chinese referring to 'improvements' they made during their production of the SKS, it makes me wonder if he wasn't just referring to the inverted take down lever. I think some of these improvements may have been more than just cost cutting procedures. I think the radiator barrel was one of them. Whether it worked or not is yet to be seen...and it may have been a minor enough improvement that it wasn't fully implemented on all late production guns.
It might just be a weird thing isolated factories attempted, kind of like the /906\ism of the 'dented' magazines. But, it still is a data point that would be interesting to see if we could nail down where these were done. It might even link up some of those factory numbers that may share the same factory....