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AK Press Fit Barrel Info

3K views 22 replies 8 participants last post by  Coils 
#1 · (Edited)
What is the diameter of the barrel where it goes into the trunnion? Want to know to make a tool out of round stock for reverse riveting the trunnion by using a hammer instead of an expensive tool. And yes some folks have done it this way including a gun smith who wrote an article about it.

Let me add I know that the measurement is not absolute I just want a figure close to see what round stock I can get and then we will lathe it down to a friction fit. So basically I want the make a mandrel to fit where the barrel goes with a few improvements.

Also forgot the add my friend has the rivet tools/punch that you can form the round heads so appearance is not an issue.
 
#2 ·
DEPENDING ON THE TRUNION IT WILL BE 23MM FOR 7.62X39 AN IT WILL BE 22MM FOR 5.45X39 SOME 223, SAIGAS ETC,

THE ISSUE WITH BUCKING THEM ON ROD OR THE BARREL IS YOU ARE NOT REALLY SETTING THEM PROPERLY I HAVE DONE IT THAT WAY BUT ITS NOT IDEAL.

I HAVE THE OLD AGI VIDEO AN THATS HOW THEY SHOW IT BY BUCKING IT ON THE BARREL AN SPLITTING THE ENDS A LITTLT FIRST.
ITS REALLY HARD TO GET A GOOD LOOKING RIVET HED BECAUSE YOUR GOING TO BE HAMMERING ON IT . USE A TOLL WITH A DIVET IN IT IF OU GO THIS ROUTE .

YOU REALLY DONT NEED TO DO BUY A ROD JUST USE THE BARREL .

THIS IS NOT THE BEST METHOD FOR DOING THIS. AN YOU MIGHT NEED A LONGER THAN NORMAL RIVET .

THE PROBLEM IS GETTING THE RIVET TIGHT TO INSIDE OF THE TRUNION.
 
#3 · (Edited)
The modified bolt cutter rivet crushing tool is ideal for crushing the short standard length front trunnion rivets. Offer this as an option vs the bucking trunnion insert device you are asking about..
Cost about $18-$20 for crushing tool of this type. Abut 60 minutes to fabricate., tops.
 
#4 ·
I am thinking of devising a tool that would be the round stock with a hole drilled all the way through it. Then drill a hole in the side for a rod to fit into that side hole. Then a tapered rod going through the end hole to push the side rod tight against the rivet. That rod would be bigger than the rivet head. The side rod would be short enough recess into the other larger round stock but the tapered rod would push it out and lock it in place when hammered to lock it all up tight with the wedge of the rod locking every thing up. The rivet head on the inside would be ground down flat enough to clear the barrel. Then start the rivet from the outside to get it upsetting then finish it with a rivet tool to round the head on the out side one. It should be very doable. My friend has enough money invested in the jigs he as bought so far we do not want to buy any more expensive tools. Both jigs he bought from AK builders he felt were worth buying but you got to stop somewhere or get gets cost prohibitive. I have an other friend with a shop that would make this tool I am thinking about. With the tapered rod tapped tight with a hammer it should lock up and not move.
 
#7 ·
Whats your point. Just because I am thinking of a different method of putting in rivets that has already been done but want to make a tool that makes it easier why not? As far as the bolt cutter route this tool probably is not any more work than that one is. My other friend has a mill and loves to fabricate stuff.
 
#8 ·
I think the joke is that this was the method most used a decade or more ago. It's not meant as criticism, there are many rifles around that were done in this fashion.

Of course the soft rivet material doesn't know the difference between a barrel and a turned rod the same diameter.....
 
#9 ·
I used flat head rivets cut down to fit into the rivet cutouts on the trunion bore for my first build years ago before there was a bolt cutter rivet tool. I actually had to grind on a couple of the rivet heads to get clearance to push the barrel back in. Then used a rivet set and ball peen hammer to form rivet heads on the outside. With having done that, I can say (for me at least) I had less time in making the bolt cutter rivet tool and installing the rivets than the other method.
 
#10 ·
I had actually pulled the barrel and removed some of the flat headed rivets from a trunion last week that had been in there since the 90's. I was able to find what was left of 3 of them that had escaped the garbage can. You can see the curve in the head of the one on its side. Unless the heads are thin, you'll have to grind them to make them fit.
 

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#11 ·
Thanks for the info> OK from what I have seen from pictures (since our parts kits are on the way and I have not seen an actual trunnion yet) the Pictures showed me areas cut out in the trunion for the rivets so the barrel clears the rivets. Correct me if I am wrong but what I am thinking is grinding down the rivet head so it is just below flush with the cut out area of the trunnion so the barrel can be put in with out being impeded. Make my tool to hold the rivet head in place. Then set up tool and hammer (TAP) the other end of the rivet to get it started and finish it off with the rivet tools to make a head on them. My friend bought some bulk boxes of USA made rivets. ( Yea I know they are not metric) We will use the right size drills to take care of that issue. That way we got some extra rivets to practice with to get good formed rivets before we do the build.
 
#12 ·
I got those rivets at ace hardware. The bolt cutter rivet tool is easy to make and well worth the effort. But, if you're going this route: cut the rivet heads to fit into the cutouts; dremmel out enough of the center of the heads for the barrel to fit in; put your receiver on and the rivets, press in the barrel; set the rivets; shoot, enjoy. I did turn down a bar so that it was a slip fit to make sure the rivet heads would clear. Here's a pic of the cutouts that are typical on non-bulged trunions. In the top picture, the slot above the flashlite is for the barrel pin. The front cutouts run top to bottem, and the rear ones run front to back. You can see the rear cutout and rivet hole in the top pic.
 

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#14 ·
wow

good luck

We will use the right size drills to take care of that issue
I don't know what size rivets you bought but do not start drilling your rivet holes bigger. the trunion is worth over $100 an if you screw with the holes in this backward riveting scheme an it don't work your screwed.
There are pleanty of bulk rivets that will fit . metric is not a issue here. you stated you don't have the kits so how are you determining rivet size?

If your kits have a barrel stub you can use it to try your back ward rivet set idea.
it may work but there likely going to be ugley as your going to be seeing the part you formed . unless your rivet heads are tightly against your insert there going to still be off the trunion when your done your still going to need to trim the inside.

You would be just as well to drive them in from the out side onto the barrel. it will work an you don't have to form a rivet head . an this is not a good suggestion its just better than what I think your trying .

you guys are sure intent on going back to 1985 n reinventing the whell that every one quit using 20 years ago.

you talking to some of the sharpest builders on the net an disregarding pretty any good advice given.

im sure you can stick in the rivets shove in a bar beat the out sides down an from a head but its not the best or easiest way to build a AK
 
#15 ·
OK they are US made rivets maybe they will fit. If not then I will buy the rivet kit. I did not buy them my friend did. I was just guessing they were bigger since they were US Rivets. I maybe trying to figure out things before we get the parts to see what we need to do. I have a tool figured out to keep the rivets tight against the trunnion. If the rivet head is flattened so it is below flush and is held tightly against the trunnion why would it not work? I am sure others have built these guns with no rivet tool like a bolt cutter or a jig to fit with a press. There was a article recently in Shotgun news that explained what rivet sizes the guy used. I have not read the article yet so I will know more when I do. Buying the right rivet size is not an issue for me if that is what it takes. So what size is the right size rivet?
 
#16 ·
If the rivet head is flattened so it is below flush and is held tightly against the trunnion why would it not work?
iM NOT SAYING IT WONT WORK iM SAYING ALL THE BENDING OF THE RIVET WILL BE ON THE OUT ISDE OF THE GUN AN WILL SHOW AN THE LIKLEYHOOD OF YOU GETTING 6 PERFECT RIVETS WITH A RIVET SET ARE SLIM . AN UNLESS YOUR TOOL IS LODING THEM SUPER TIGHT TO THE TRUNION THERE NOT GOING TO BE SET TIGHT .

iD PAY LESS ATTTENTION TO SHOT GUNNEWS AN MORE TO HOW ITS DONE BUY GUYS WHO DO THIS EVERY DAY WITH GOOD RESULTS. ITS GREAT TO THINK OUT SIDE THE BOX BUT 99.999% OF THE STUFF ON THESE HAS NOW BEEN FIGURED OUT TO WERE ITS FOOL PROOF AN MUCH EASIER .

THERE ARE THREADS HERE OIN GETTINGHTE RIGHT RIVETS IN BULK THERE ARE THREADS HER ON MAKING THE RIGHT TOOLS. DO A SEARCH LOOK THROUUGH THE LIBRARY . THOUSNADS OF GUNS HAVE BEEN CORRECTLY BUILT THIS WAY.
 
#17 ·
Yep; Matthews is a slimeball hack who steals ideas from guys on the forums & writes that he came up with them.
If the rivits you bought don't seem right, PM me & I'll send you some that I use for free.
You might consider buying the great instruction disc that totenkoph sells here. Good stufff from someone who really knows what he's doing.
There are NO BETTER builders that what you have here at Gunco!! These guys pioneered AK building & are standing by to help you build it right.

Brad
 
#18 ·
Here's the link to the bolt cutter rivet tool. http://www.gunco.net/forums/f163/biy-rivet-squeezer-boltcutters-979/

I sold the set I made probably at least 5 years ago,which was two computers ago so I can't find a pic. They only differed from hcpookies design by using a 5/16" thick by 3/4" square piece with the rivit divot welded to the anvil jaw which allowed me to modify everything and just weld it in place once it was centered. It probably took me 30 minutes from start to finish to make them. HCPookie deserves a halo above his name for figuring these out.
 
#19 ·
#22 ·
So instead if starting a new thread I figured I will ask my question here since it's related.


Looking at my front trunnion I can clearly see how far the old barrel was pressed in. I have a virgin barrel on the way, so my question being: Is the mark inside the trunnion a good starting point on how far to press the new barrel in?

Im going to end up using one of the all thread methods to pull it in, and my fear is going too far initially, then having a hell of a time backing it out. Im going to rent the gauges and headspace properly, I just want to get close and avoid as many headaches as possible.
 
#23 ·
You can use that as a reference.
But I wouldn't use it as a close reference. Your going to need to remove the all-thread multiple times while checking head space. And don't worry if you go too far, worst case you'll need to buy a $20 power steering pulley puller to move the barrel back out.

Remember you can check head space with the trunnion out of the receiver, but then you need to remove the barrel again for riveting. Well unless your doing a screw build, then you just need to remember to tap the threads before you start anything.
 
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