Hello everyone, it's been a while since the last update. I've got a tiny bit of material to share with you before finally finishing the RPD build (it's coming).
Today we will talk about the differences between old style and new style Polish underfold parts. The differences are minor, but make for an interesting study in evolution of AK production. Before proceeding any further, I must give credit to Eric Fordon of theakforum.net for a great insight of the subject matter contained in this article.
In general, newer parts are machined, while later parts are cast with minimal machining. Here are two front sight blocks (new = top, old = bottom). Notice the casting marks, as well as some lightening "cuts" on the new style.
Here are the gas blocks. On the left is the new style, while on the right is the old.
Here are the lower hand guards. The old style is the darker one. Notice the metal horseshoe in the old, and the leaf spring in the new. Also, the old style has a serial number on the left side. The wooden tab that goes into the receiver under the barrel may be thicker on the old style.
Here are the hand guard retainers. The old style is on the left, and is milled, while the new style is on the right and is cast.
The slant breaks. The old style is on the right, while the new style is on the left. Notice the lack of what I am told is a wrench slot in the old break.
The return springs. The new style, with an anti-unlock tab is in the back, while the old style is in the front.
The rear sight blocks. RSBs are more or less identical, except for the rivet on the gas tube retainer. The old style is on the left (with a more protruding rivet), while the new style (with a flat rivet) is on the right.
Here are the top covers, but honestly I could not see much difference between them. This pair is the most distinct that I could find, with what I presume to be the old style on the bottom and the new style on the top.
Here are the trigger guards. The old style is on the left, and the new style is on the right. Notice the hump on the new style.
Here are the rear trunnions, this is probably the largest difference in parts between the old and new sets. The old style trunnion is fully milled, while the new style is stamped/bent and spot welded.
And finally, here are the folders themselves. The new style has 5 spot welds, and unequal length indents (on both sides of the spotwelds), while the old style typically has 3 spot welds and equal length indents (they look a unequal in the picture for some reason). There is an additional possibility of a combination of 5 spot welds and equal indents (not shown), it was seemingly produced under the new procedure using old parts. The loops in the bottom picture are different too, the left one being the new style, while the right one (with spotwelds) is the old style.
These are all the distinctions I could find, but I suppose I could have missed one or two :) so please don't take this to be an exhaustive list, simply what I had seen and taken pictures of.