Polish under folder Ak issues (home built)

[John in WI]

I'm wondering if I could get some sage advice from someone who knows about setting up a home bulit AK.

About 2 years ago I bought a parts set from AK-Builder for a Polish underfolder AK. http://ak-builder.com/index.php?dispatch=products.view&product_id=30127

I built it on a Marsh Hawk pre-bent reciever blank, and used rivets for the assembly.

The issues I'm having are that the rifle frequently has a "failure to eject". Normally, the empty case along with the live round stripped out of the magazine go forward which jams the weapon. I'm not sure what would cause this. If I yank back on the bolt, it doesn't seem to have an issue ejecting live rounds, but about 1 in 6 seems to jam on live firing.

The other problem I'm having is that I put 20 rounds through it today and they were ALL over the place. 8 of them were perfectly sideways and 2 of them looked fairly straight. I was firing from 25 yards using "Military Classic" 7.62x39 ammo.

So now I have an issue. Since it's a home built, I cannot sell it or otherwise transfer ownership. I really like how the rifle handles, but the complete lack of accuracy and reliability is a serious dissapointment. So I would really prefer to figure out what's wrong with it and get it working properly

Where would you guys start sorting out cycling and keyholing problems? I guess first I need to slug the barrel and chamber and see what dimensions I'm looking at. I hope I can find commercial ammo to fit it properly!

But the ejection problem I'm not sure what to do. It does bind a little bit, where the bolt rides on top of the back of the hammer. I'm wondering if I need to shave it down a little bit?

The other info that might be useful. The compliance parts include a new US made barrel/muzzle device (I checked the brake--there is a good 1/8" of clearance all the way around it and the barrel and no signs of contact). The trigger group is from Tapco and the bolt and carrier along with the other harware came from the original Polish kit.

So help me out guys--how do I achieve the well desereved reputation for reliability!?

[Larry Gibson]

Almost impossible to advise w/o looking at the AK, sorry.

Larry Gibson

[NickSS]

The tumbling bullet sounds like an over sized bore to me. Hve you slugged the bore? It is basically made of salvaged parts from used guns so who knows. The failre to eject sounds like either your piston is loose or more likely you ejector is not engaging the shell correcty to kick it out of the gun. Just a guess on my part without seein gthe rifle.

[historicfirearms]

How far are the casings ejecting when the rifle does cycle? I'm wondering if maybe your gas port hole isn't big enough or maybe the hole and gas block are not lined up exactly, so the rifle may not be getting enough gas to operate. My AKs really throw the brass, seriously over 20 feet with full power loads.

[Mooseman]

By your description it is failure to EXTRACT...The spent case stays in the chamber, then the bolt cycles and tries to feed another round.
That tells me it is either a sticky chamber (needs polishing) , a weak extractor spring or bad lip on the extractor, or that ammo has the laquer coating that is gumming up when hot in the chamber.
IF the spent round is being extracted,and not ejecting, then you need to check the left slide rail Ejector and make sure it is riding deep enough in the bolt head groove, and if that Receiver has "spread" a little it will have to be squeezed back together so the lip catches the rear of the spent cartridge as the bolt comes back to kick it out. Check for a chipped ejector face too.
Rich

[RU shooter]

Sounds like an ejector problem , possibly the wrong one (ak74) or just not installed in the proper position or needs some tweaking possibly? Does it malfunction when you cycle the action by hand ?

[John in WI]

When I work the action by hand it seems to throw the cases a good distance. During live fire, for the empty cases that do eject properly, they are thrown at least 15 feet from the rifle. I noticed last weekend that what seems to be happening is that occasionally the empty is extracted from the chamber but not ejected from the rifle. And the actual jam happens when the bolt slams forward with a live shell partly wedged in the chamber but an empty making it unable to go in.

I've been doing a lot of reading on the AK-files and they suggest some things to try. One is that there is some "drag" when the bolt is pulled back. I hand fit the upper reciever using files and finally stones and it may need just a hair more. Also the bottom of the bolt seems to drag excessively on the hammer. They said that it can be polished and/or shaved down a hair if needed. Either one of those conditions could use up enough of the bolt's rearward force to make ejection unreliable. The fact that it works about 90% of the time seems to indicate that it's close--just needs some tweaking.

I spent a lot of time fitting the ejector into the bolt head groove and have it so that it just barely clears without binding. It's as deep as it can go--the final fitting took a long time with some 220 sandpaper to get perfect. Then I removed it and heat treated it (It's 4130 steel if I remember right). That still looks good--not chipped or bent.

So, I suspect it's a little bit of binding robbing the rearward motion of the bolt on firing. The plan this weekend is to totally remove the guts and clean everything very well and re-grease/lubricate it all. Look of obvious burrs and defects, and look for places that seem excessively polished that would indicated surfaces wearing against each other that shouldn't be.

As far as the key-holing, I wrote the manufacturer of the barrel to ask what the specs are. From what I read some of the combloc barrels can be seriously oversized. Someone claimed that it is to compensate for thermal expansion caused by firing full auto? (is that a line, or is there some wisdom in that?).

Anyway I asked what is the barrel supposed to be, and what ammo does he recommend using in it.

I really would hate to switch out the barrel as it would cause me to destroy a LOT of work involved in rust-bluing the reciever, riveting the trunnion... I really hope I can just find an ammo make that it will digest without tumbling. I didn't build it to be a tack driver--but I'm literally not sure I could hit the broad side of a barn at 100m with it!

Thanks for the suggestions--I'll have a couple hours to look things over this weekend and hopefully slug the barrel so I can give some real numbers.

[Mooseman]

The Spent cartridge would have to be missing the ejector to stay in the bolt gripped by the extractor. SO something isnt right with either the extractor being gummed up with powder residue, etc, or the bolt head is for some reason moving to the right away from the ejector blade.
If the gun is cycling and stripping a round from the mag, then drag is not usually an Issue, and cocking the hammer and riding backwards over it helps to slow the bolt to keep it from slamming hard into the rear trunnion.
Remove the magazine, Pull the top cover, remove the spring assy.
pull the bolt carrier back until the bolt head is lined up with the ejector.
With your fingers, wiggle the bolt head left and right to check for play in this position.
It should only move back and forth less than 1/32 inch, the bolt carrier should only wiggle about 1/16 inch at the rear or at the gas piston section.
The top of the ejector blade should be about 1/8 inch protruding inside the bolt as viewed from the ejection port.
Pull the carrier/Bolt assy and with your finger, you should be able to pull the Extractor back as far as it can go with some force, but fairly easily. Make sure it is free and not gummed up or caked with powder or Cosmoline.
I have built Lots of Ak's and My Polish Underfolder is My favorite...It has yet to fail me.
Rich

[John in WI]

Thanks Rich--I know this Polish AK has it in her--it's just my first build, and I don't have all the bugs worked out yet. I will keep in mind that you're a veteran builder though. The guys at AK-Files are knowledgable but over here at Boolits I get a lot less attitude. I'm a complete newcomer at this game--I admit that. But at some point every expert was a new comer!

thanks again--I'm going to spend some time stripping it down, degreasing and cleaning the heck out of it, and putting it back together with clean oil and really carefully look over the mechanism. A buddy of mine loaded up a handful of dummy 7.62x39 rounds with holes in the side of the casings, no powder and fired primers in the rear. That will let me test the action without fear of any "accidents", but they should have the exact dimensions of the real thing.

What still troubles me is the other big problem it has--the keyholing troubles. I need to fire it at longer distances and see if they straighten out in flight. But still, the accuracy seems terrible with the 3 brands of ammo I tried. But that is going to require slugging out the bore and seeing if it's seriously oversized for the boolits I'm trying to run down them.

thanks again for all the help--I would hate to think I have a really cool looking paperweight on my hands here.

[John in WI]

Well I just put the AK back together. I gave it an incredibly careful cleaning. I took the bolt assembly to the lab and used the sonic cleaner to get it spotless. I sonicated the trigger parts, polished the rails with 800grit paper until they looked like mirrors. I brushed out the gas system, poked a wire through the gas port, and scrubbed out the inside of the reciever with solvent and a tooth brush. So, a jar of Hoppe's later, I have it all back together. Too bad it's pouring rain and I didn't get a chance to test it, but I hope this helps.


Can anyone give me specifics on "slugging" the barrel? Do you just melt a few boolits-worth of lead in a ladle and pour it down the bore, then push it out with a metal rod? Does it matter what alloy you use? I have an alloy with fairly high tin content that should melt at a low temperature. I also have some steel rod that I was going to cover with a layer of electrical tape to keep it from scraping the bore.

What do you plug the barrel with, to keep the alloy from going all the way through?

[obssd1958]

John,
Slugging the barrel is usually done by forcing a lead slug down the barrel, and then checking the two diameters with an appropriate tool.
I use a .320 round ball from a 00 buck shotgun shell to slug all of my .30 caliber barrels. I run an oily patch down the tube and lube the round ball with Imperial sizing lube. Next, I start the ball at the muzzle with a soft faced mallet, then use a short piece of dowel to get it 3-4 inches down the barrel, then a brass rod to push it the rest of the way through.
Piece of cake - takes just a few minutes.


Don

[HATCH]

I have built and owned a few... haha

U have a us made barrel.
Its ****. Thats why you are having so many issues

Go to theakforum.net
Do some reading. thats were the pros go.

I will take an original commie barrel any day of the week over a us made replacement....

You got headspace gauges??
Did u heat treat the ejector tab??

there are way too many issues to armchair repair it without seeing it.

And on the home made reciever.
U can sell it. U just got to put ur name and city/state

The trunion should have a serial # on it from poland. U can use it




sent from my mobile

[John in WI]

Oh, ok. I was confused about that. I saw one of the gun shows on cable and they measured a chamber by pouring lead into it, and knocking the plug out.

I don't have any loose 00, but I do have some commercial rounds that I could probably steal a ball out of and re-roll crimp when I'm done.

[obssd1958]

Hey John,
When they measure a chamber, they should be using a product called cerrosafe. It melts at a very low temperature, shrinks a little after cooling (very important if you want to get it out of the chamber!), and then returns to the chamber's dimensions within a predictable time frame, so that you can measure all of the dimensions of your chamber accurately. I've done this a few times, and used a patch on a cleaning rod to limit the depth of the casting.
Some folks do measure some of the chamber dimensions - throat, leade, etc. - by "upsetting" a chunk of soft lead between a solid obstruction (case full of lead, or some such) and a brass, or tape covered steel, rod - at the point in the chamber that they want to measure. Never done this, but some here contend that it will give more accurate dimension info than the cerrosafe - your mileage may vary!!

Don

[lmcollins]

I once read where Harry Pope "consulted" at Spingfiel Armory and taught them to slug barrels by his method.

He taught them to take a slug of less than bore size, put it down a lubed bore, and "upset" it with metal rods from each end. Then push the slug out of the bore with one of the rods. I'd say that a pounded-around oversize round muzzle loading ball would due fine, and "upset" should work in a great manner. Take it all from there. I think I might have gotten this info from Hatcher's Note Book or one of Ned Roberts books.

Two duct taped steel rods from Home Depot should work fine for "upsetting." Make any size large lead ball fit by pounding it around lightly.

[John in WI]

I think I am going to try that. I have some #1 buckshot (.30) that should work if I give it a gentle tap to flatten it out a bit.

I think I am going to try and buy some other brands of commercial ammo today and see if I can find one that shoots well. Or at the very least, something with brass cases I can use if it comes to reloading some properly sized boolits.

I wonder if anyone would give me wierd looks if I brought my micrometer to the store and started micing ammo out of the box?