2. The cleaning rod is an early, female-threaded rod at the large end;
My LB #061 has the funky threaded cleaning rod hole in the big end
7. Tappet/piston extension is manufactured with a flat, on which the drawing number is placed (not sure if this is common on Yugoslav SKSs);
My LB and "B" M59 series has the flat, my "C" M59 series and M59/66 does not
6. Electropenciled "428" on the gas tube;
I have no numbers on my LB gas tube or piston
3. Secondary electropenciled "31" on the bolt carrier;4. Secondary electropenciled "33" on the bolt;
Both my LB bolt and carrier are blank....with exception of assembly numbers.
6. Electropenciled "428" on the gas tube;
Same deal. Interesting low number though... Guessing a B series m59
Whoa... hold up.....stop the press, whats that again.......... Uhm... there have been no M59s documented above 101.... did I miss a memo?
Long Barrel Yugo M59s are supposedly #001-#099, the "B" series M59s started #154xx give or or take.... We pretty much know serials 15500 to 23700 are missing, and C series M59 picks up around 238XX...
No later than 100 3 digit, 4 digit or 5 digit earlier than 154xx have ever been photo verified...
Now...........is someone possibly promoting an "A" or very early "B" series M59.... My LB magazine has a 115 electropenciled on it.... could it be... do we need to rehash this whole 3+ year old thread...http://sks-files.com/index.php?topic=1878.0
I read your thread on GB forum and while I think the idea of these LBs being test subjects for pressures etc is interesting, I would have to agree with Justin (kissvids) on the matter of ot likely not being the case. In addition, I would tend to think the LBs were the first produced in Yugoslavia. It would seem rather redundant to experiment mid production with a dif front sight design. Also, mid production guns had serials etched not EPed on the carrier, cover, and trigger and I would expect to see the same on the LBs if made mid production. Same goes with the serial roll stamped into the bottom rear left of the receiver..... Its just odd and at no other point in production have they done anything like this. Then you have the assembly numbers.... All super low numbers aswell. This would tell me they were not made later along with rifles having much higher assembly numbers. Lastly, as you have seen with your oddball LB having a standard front sight, they had no problem numbering a n LB with a later C series higher serial number if that was when it was made. So in short..... Its all about those low serials.
As far as gas pressure and volume.... the port on my LB, both M59's and M59/66 all look to be the same size.. the only rifles I have seen with an enlarged gas port are the short barrel Chinese paratroopers.. My understanding it's to get the gas system moving sooner and faster due of the lack of barrel after the gas port which reduces gas pressure/dwell time in the barrel. So a larger port = more gas volume = so they basically over gassed so it will cycle just a hair sooner and faster..more like a Ak, with it's over gassed gas system. Also some Chinese paratroopers have a slightly shortened gas system, where in the length of barrel you place the gas port could affect the gas system pressure and exact timing, possibly more than the port size or barrel length I would imagine.
The M59/66 looks to have used the same standard port size as the M59, only you can shut it off, it's only needed to cycle when firing actual ammo, not grenades. With regular ammo and an intermediate sized cartridge, I'm sure there is not an overly massive increase in barrel pressure with that extra inch and a half or 2 inches of barrel, I'm pretty sure it''s nothing that the robust gas system couldn't handle. And also, the gas port is possibly past the peak pressure point in the barrel, it's just hot expanding gasses at the gas block, also some where in the whole equation, there will be a point where barrel friction over comes the expanding gases..Remember, there are Ak pistols with a 10 inch or something barrel, and they cycle, albit very loudly, their gas system port would also be before the point of peak barrel pressure, because it seems if they got any shorter, the gas system goes stupid due to the extreme pressures..
Also just to throw it out there..... an RPK has a 23.5 inch barrel, an inch longer than a LB and over 7 inches longer than a standard AK-47.. it uses pretty much the same standard style AK gas system. The RPD has a 20.5 inch barrel.. while your standard issue Ak, AKM have a 14 to 16.5 inch long barrel.
And in my mind, maybe just a wild arse guess....if it did allow gas system pressures to raise ever so slightly due to the longer barrel.....that may be a good thing... that could give more tolerance in the gas system for leaky tubes/gas blocks, it in theory could have a little higher rate of gas leakage, and still cycle, where a regular 20.5 inch barrel with the same gas leakage rate wouldn't. But.... I don't see it.. due to the fact in the micro milli seconds of dwell time the bullet is in that last say 2 inches of barrel, there is not enough time vs volume of gas that can get through the small gas port, much less enough to effect anything.