Cast Receivers: Machined to Specifications After Casting?

[jmaurer]

Some time ago, I made a guess that cast receivers appeared to have been machined to final form:

Thanks for checking your files, Running-man! In scrolling through the photos again, something jumped out about the sides of the receiver where the barrel is pinned. It definitely looks as if the receiver was produced oversize and was intended to be machined to final specification; note photos 37 and 47 above:


On the normally round, most forward part of the receiver that houses the chamber end of the barrel, you can see small flats that appear to be the result of planing the receiver sides, where on conventionally-produced receivers, this area is essentially round, as far as I can tell with a quick review of a few random photos of other rifles.

Edit to add:Padams8888's 1972 DB Shenyang City rifle also has these flats; the images he posted clearly show machining marks spanning the main, largest flat side of the receiver and the forward-most round part of the receiver:
https://sks-files.com/index.php?topic=4345.msg48429#msg48429

However, his 1970 Arsenal 0221 rifle does NOT have these flats:
https://sks-files.com/index.php?topic=2270.msg26224#msg26224

In browsing recent auctions, I came across a couple of rifles that appear to have cast receivers, and unfortunately I only saved images from one of the auctions. What's intriguing about those rifles was the stamp that appears at the left rear of the receiver; a random internet Chinese character translation seems to indicate the following could mean "flat" or "planar", possibly supporting the notion that the receiver was machined after casting (if indeed the receiver was cast):



To determine if the rifle with the above stamped character was cast, please see the following two images:





Can anyone offer confirmation of my stab at translation of the character, or a better translation?