[Papa AK47]

Looking good! For those who don’t know, the 90 degree Zastava gas port in the barrel doesn’t line up with the hole in a surplus grenade launcher gas block. So experiments and modifications (NOT to the barrel) are required.

Thanks @Caverpete!
Here’s a few pictures of the original gas block and the test gas block. And the test gas block compared to a surplus gas block that has not been modified.

 

[Papa AK47]

That is smart,,, many people just drill through the gass block at 45, it still works but I like your method and thank you people can learn from this. Absolutely good job bud. This is why I love this forum it's because of people like this sharing knowledge and skills. Thank you Papa and Pete we can always learn from you 2

@Caverpete deserves the credit as it was his idea to create a channel going farther back to reach the gas port in the barrel.

 

[Papa AK47]

milling a gas transfer slot for mismatched ports in the barrel is a common mod as well./ No, it doesnt hurt anything

That’s good to know. Thanks for the info. I’d like to know more info about that.

 

[Papa AK47]

So, I have a new problem with this project. Shooting with the stock folded under or from the hip, it won’t cycle. It drops brass about two feet away. Shooting from the shoulder it ejects about 6-12 feet. I did have a couple drop a couple feet from me from shooting from the shoulder. I need more gas. Eat more beans!🤣

I was thinking from what I had done that the gas chamber area is now too large wasting gas but I truly have no idea as this is my first experience with this stuff.

From the beginning from the factory with the original gas block it has always had a weak ejection. I’m not sure where to go from here. I wish I would have checked the barrel port hole size when I had the gas block off. My Maadi and my Polish WBP Jack launches brass into the next county. Those two will function reliably under most situations and ammo choice.
Picture from when I had the components off the barrel.

 

[Papa AK47]

When firing from the hip, you end up with a situation analogous to limp resting. As the rifle is not fully supported, recoil energy it is exspended recoiling the rifle instead of being utilized in the ejection cycle

I understand that but it would cycle fine when shooting from the hip before changing out this gas block. It had and has a weak ejection. I’m thinking I might need to open up the gas port on the barrel. Won’t know that for sure until I try a few other things and remove the gas block to try and determine if the gas port in the barrel is too small.
My Maadi and my Polish Ak cycle fine shooting from the hip. They still have plenty of gas from the hip or the shoulder.

 

[Papa AK47]

First thing I’m going to try is a bigger valve on the gas regulator. See if that helps.

This 194 gas valve will be the one to try.

This last picture is the original one in the gas block now that I’m not getting enough gas flow.

 

[Papa AK47]

I can run a 9/64 bit into the gas block port and it still has a little slop. And these Yugo surplus barrels are drill with a little bigger that a 9/64 bit.

 

[Papa AK47]

Also, how is your piston fit in your gas block?

What am I looking for as far as fit?

 

[Papa AK47]

I would check your original Piston Cup against replacement gas blocks cup inside diameter, check for corrosion and erosion, and do a comparative fitment to see how loose the new one is versus the old one. Off the top of my head I can't remember what the ID diameter is supposed to read, it used to be fairly common to find these highly eroded, they did go through a war

Thank you for your help. I did check this gas block as I do have one that is all rusted and pitted. This one is in excellent condition.

 

[Papa AK47]

I put in the bigger regulator and tested it. The good news is it ejected a little bit farther but still not enough gas to get it to cycle reliably unfortunately. I will remove the gas block and check the barrel gas port and see if it needs to be opened up.

 

[Papa AK47]

Ok, I removed the gas block today and checked the barrel gas port. It is 1/8. I drilled it with a 9/64 bit. I went out to test it and it cycled perfectly. From the hip it ejects 5.5-6.5 feet and from the shoulder it ejects 9.5-10.5 feet. It functioned and cycle perfect. It just needed more gas.

 

[Papa AK47]

I did my M72 with 1/8. I checked 4 original barrels on m70 and all are 1/8.

My two Yugo military surplus barrels are 9/64 as well as the surplus gas blocks. 1/8 was not giving it enough gas.
All 9/64.

 

[Papa AK47]

That is weird,, 4 of my do measure 1/8 and I have that size on all 3 builds. Hmm.. but hey you can always open it more but if 1/8 is not giving you problems I wouldn't touch it because my cycle perfectly fine on rapid fire as well and 100 rounds through each. Even on cutout M72 kit gass whole was 1/8.. Maan 9/64 to me is big 😆 I guess yugoslavians used it when they run out of 1/8 size and said fuck it lol it's ok as long as you can't stick your dick through it 😅 Hey Pete!! What you think on this bud.

A gas port cleaning tool won’t even fit 1/8. And my Maadi and my Polish AK are 9/64. And no, my rifle would not cycle with 1/8 reliably. I have 4 M70 gas blocks and all are 9/64 as well as the two barrels.

 

[Papa AK47]

I agree, don’t mess with it unless you have to. I had to unfortunately.

This guy goes even bigger-

 

[Papa AK47]

Good job @Papa AK47, at solving the problem. I drilled my M70B1 & M72B1 with the AK Builder drill bit, 0.1285 or #30. Both cycle and eject well. All my other yugo builds have original barrels.
View attachment 405223

Thank you!
I can’t figure out why this particular rifle doesn’t want to cycle very well. It had a 1/8 gas port on the barrel. It was relatively weak from day one with the original gas block. But it did cycle. When I swapped out the gas block it didn’t want to cycle reliably. So that’s why I opened up the barrel gas port.