Apologize for continued questions -- obviously I'm weighing options for what to do with Bulgarian kit that got delivered last w.e. from ORF. (By the way, the condition of the kit and the general workmanship is excellent. I don't know if the price is competitive or not these days, but I'm very pleased with the product. Thanks, ORF!)

Basically, I'm considering shortening the barrel of my -74. What I'd like to do is shorten the barrel enough that I would use the combined Bulgarian gas chamber/front sight block, and permanently attach a 4-piece cone-and-barrel style flash suppressor. The resulting overall barrel length will be a tad over 16", and I think it would have an interesting profile.

Questions:
How sensitive is the AK gas system to different gas port positions? The length from port to muzzle is the same as the -74U "Krinkov".

Can anyone provide references for gas port configuration (how big, where is it clocked, etc)?

Has anybody else done this or something like it?

Many thanks.

not very sensitve.

just find a drill bit that fits the existing hole, and go for it.

use a needle file to fix any burs before sending a bullet downrange.

I would keep the same port to muzzle distance though. If you shorten that, you are asking for trouble.

Quoted: not very sensitve. just find a drill bit that fits the existing hole, and go for it. use a needle file to fix any burs before sending a bullet downrange. I would keep the same port to muzzle distance though. If you shorten that, you are asking for trouble.

Ok, so what is the port size of the AMD65, and the Yugo krink?
These two have barrels way shorter than stock.

yea, they are already pretty short. I think an AMD is about 1.5 inches.

Just don't go to much shorter.  I would deffinitely NOT go shorter than one inch, or whatever a krink is...

And if you want to get technical, port to breach and port size also matter, on extream mods (like that 6 inch barrel mod I saw.

Quoted: yea, they are already pretty short. I think an AMD is about 1.5 inches. Just don't go to much shorter.  I would deffinitely NOT go shorter than one inch, or whatever a krink is... And if you want to get technical, port to breach and port size also matter, on extream mods (like that 6 inch barrel mod I saw.

I take it you are talking about how far back from the standard AK47's port the others are.
In which case the AMD is about 1 1/8 inch farther back, as thats about how much shorter the piston is.

I was wondering what diameter the gas port hole is itself.
Do they drill a smaller hole the closer you get to the chamber?

that is a very good question.

On my 8 inch barrel build, I just found whatever drill bit I had laying around that fit fairly snugly into the pre-existing port, and drilled it with the gas block installed (AMD mod)

It's about 4.5 inches closer to the breech that the previouse port.

Then I left a full two inches of "port to muzzel" just to be sure.

It works fine. I am sure I could have used a smaller port, but I want reliability, and the way to do that is to keep everything working strong.  

Now, if I was going any shorter than that, I would deffinitely make a smaller port. like, say on a 6 inch barrel... ... I would drill a smaller port, then test, and drill slightly bigger ONLY if needed.

Or, if I was making the port to muzzle distance smaller, I would go with the same size on a 6 insh barrle.

OR say, on a six inch barrel with a 3/4" port to muzzel, maybe you would need a slightly bigger port (although I doubt it) and I wouldn't drill it bigger unless it was obviously causing some problems.

Many thanks to all for sharing your experience.

I've seen a couple of radical configurations that worked OK, but just the same I don't want to do anything risky as my kit is exceptionally nice.

One of the things that the -74U ("Krinkov") does is to have an expansion chamber with a flash-suppressing cone on the muzzle. Strictly speaking, the Krink port and muzzle are VERY close. The muzzle device adds some back pressure to help insure functioning.

The Bulgy cone-and-barrel flash suppressor is supposed to do the same thing, as well as direct the flash and blast forward of the muzzle.

Anyhow, I'm still thinking about how I want the build to come out, so no decision just yet.