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MY SONS SWITCH BARREL AK BUILD IDEAS

16K views 114 replies 24 participants last post by  twa2471 
#1 ·
Im starting a build for my son and he got a box of AK parts and barrels and stuff for Xmas. it will be a 243 0r 260 remington loaded to light pressure.
Its going to be a light weight sporter and I want it as light as i can make it besides the heavy m70 trunion. this will be a outside the box build over the next year were he helps build it. He is 9 and will be able to shoot deer next season. I plan on letting him do as much on it as he can including some of the machine work that way he will know whats going on and how it all works and get some Shop time with Dad. It will have gas shut off as well and he will be shooting this as a non semi auto at first. Baby steps here.

Hes pretty sharp and noticed I had three barrels in the box, a 243, Win 260 Remington and 308 WIn there all model 700 take offs. he asked why there were three barels and I told him we were only going to use one but I hadent decided what one and that id keep the other two. Well hes not one to give stuff back that he just got, so he says way not use them all and just change them.

I have thought of several differant switch barrel assembly set up's in the past but they all required seperate trunions on a screw build. So got to thinking about a threaded barrel set up.


it looks like a 1"-12 thread can be used on the 23mm trunion if the bore is opend up to .9219"
that is .016 more than the factory bore. thats not much metal to get things right with with the boring bar if it dont cut good on the first try. the Yugo bore is not interupted like other trunions were there are hollow spots between the barrel and the trunion. aside from the barrel pin there is no interuptions. I really wish I had a virgin trunion to work with. the RSB will need to be removable or able to slide forward or you will not be able to unscrew the barrel. I was thinking of useing a barrel nut like the savage bolt actions and all barrels will need to be timed but that should not be a issue as once there head spaced correctly they will always be reinstalled in the same place every time.

I have seen were a guy threaded a 410 Saiga in conversion to a 500 S&W so I know it can be done. I think the model 70 Win uses a 1" thread .

this build is going to have a custom Aluminum RSB and likely a GB so I a dont have to worry about traditional looks in fact the less it looks like a AK the better for this build. people get nervious with kids shooting AK,s for some reason LOL.

I was even thinking with a differant bolt I could even do a 410 SG barrel for it.
 
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#2 ·
Could you slit open the top of the RSB sleeve and turn it into a pinch nut? Loosen a couple of screws, pull the loose RSB forward, remove barrel.

Slide the RSB onto the new barrel, time and lock the barrel, then time the RSB and tighten it with the screws, done.
 
#3 ·
I was actually thinking of a custom RSB/optics rail that would stay with the trunion and then I could keep a chart of what scope settings work with what barrel and then I would not need to sight it in every time. or if a side rail is used ( somthing Im not a big fan of ) I would just need a gastube dust cover mount holder like on a Saiga 410.

there are a bunch of ways mount a RSB . the barrel pin holes will not be used so they could be tapped to hold a GB or it could be sanwitched enbetween the barrel and trunion and then also held with screws so it retains zero during barrel changes. I have a few L1AI Gb,s so I could use them on all the barrels but the super heavy varmint set up were to Od will need to be bigger and there are heavy barrel L1A1 block avaliable. Im starting to like this idea more and more. I could go from a 16" barrel super light weight carry deer rifle to a 28" 1" no taper barrel 260 rem 1000 yard varmint set up in minutes.

Im actualy now staring at my Sagia 308 and thinking what if????? and then I could shoot 61,000 PSI loads. maybe even 300 WSM loaded down slightly to keep the pressures in line. :)

whats the inside of a 308 Saiga trunion look like?? is there cavitys or is it uninterupted???? Judging by the rivet placement Im guessing its got cavitys :(

how ever there was the 410 Saiga conversion to 500S&W that got threaded. HMMMMMMM
 
#5 ·
You could toss the RSB and use a Galil or Valmet gas tube. You'll have to file the ears on the Yugo trunnion to accept the dovetails.

Most Valmets and all Galils used top cover mounted sights. A few Valmets had the rear sights on the back of the gas tube, more or less in the same position as with a conventional RSB.

With my Yugo trunnion, it looks like a 15/16-12 tap might work. I found them from a couple of places online for $35 or so.

There are some pictures around of a switchbarrel AK using an Uzi barrel nut and flanged barrel setup. You could turn the threads onto a bushing, press it into the receiver, and anchor it with the stock Yugo pin. You might have to clearance the pin if it hangs through into the ID. With the Uzi setup, you could then just slip the barrel in and tighten the nut, no separate headspacing step needed.

If you're not working with a blank where you could cut the flange to start with, you could machine a collar, heat it, and slide it up to go into a .003" or so groove in the barrel, where it would lock in place.
 
#6 ·
I was going to mention interrupted threads as a good idea. Should work well, although you may have to use some acme-style threads to get good interface. Something thick.

Another idea may be more simple than you expect - do you know how the PKM barrel locks? It has a standard style trunion that is fairly long, perhaps 4" long. The barrel slips into position and a "wedge" locks it in place. The wedge is set on a cross-ways dovetail. You're supposed to use a bullet tip to slide it sideways, but if you were to add a hinged or curved handle of some sort on the side, you could set it so that the handle pries it sideways. Kind of like a prybar or crowbar. Something to pull the wedge loose after the barrel heats up. The headspace is set and THEN the notch for the locking wedge is cut into the barrel.

Following this idea, you could use the barrel pin hole as a starting point for a wedge. Maybe square out the hole so the barrel is notched with a larger area than just using the hole as-is.

I think Ilya's picture gallery has some of the PKM pics you should look at.
 
#7 ·
well I did some investigating and remington 700 barrels use a 1 1/16 -16 thread that means a trunion bore of almost exactly 1" depending on thread engagemwnt and tightness. so 23 mm trunion would need be opened up about .095" that would give some wiggle room on getting a cutter on a boring bar dialed in ferfect before a final cut. there is pleanty of meat arond the bore on a yugo trunion.

I like the idea of retaining the remington thread size at most barrels that are cheap take offs are remington. the threads are to short unfortunatly but the good news is that they can be used to start a tap straight if one should decide to not use a lathe to cut them.

there are special taps and dies avalaible for about $50 each. brownells has them also but there more. i havent serched every were yet. there are other threads that might be closer small ring mauser uses a 1.10"-12 thread that requires 1.018 hole.

I have a Howa barrel here and th threads are odd the od is around 1.020 but it looks like it would be pretty close to a 23mm hole to be threaded. ruger M77 is close also but might be to small around .995 od not sure what the TPI is but i thing its 16 but .925 would be the needed bore for it so 23mm is .020 to small it looks like. dammm

You could toss the RSB and use a Galil or Valmet gas tube. You'll have to file the ears on the Yugo trunnion to accept the dovetails.
were are these avalibale at?? any one got a picture?? this sounds iseal to keep the weight down. he can barely hold up a 22lr bolt action right now so I really need to cut some weight and hope he grows in the next year.




To determine the proper drill size for 75% thread on a special pitch tap use the following formula:
Drill Size = Major Diameter - (.975 divided by the number of threads per inch).
For example, with a 1/4-32 tap, .250" - .0305 = .2195 (7/32" or #2 drill size).

Metric tap drill sizes are the diameter minus the pitch (e.g. 42 x 1.5 tap uses a 40.5 drill).
 
#47 ·
there are other threads that might be closer small ring mauser uses a 1.10"-12 thread that requires 1.018 hole.
I have used several REM take offs for small ring mausers but they cant be used for LR
 

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#12 ·
I got my Galil tube from Apex. It was $35, but I couldn't find one anywhere else at the time.
Thanks Im going to check that out. if I can get it to work with my trunion this my be the ticket for a couple things I have in mind I may just mke some thing simular. I assume it dove tails into a special trunion some how I need to get look as a GALIL.
r guns has virgin trunion... for the yougo.. B2B
Thank you I may need a few. Ill likley screw some thing up LOL.

Id really love to find a 308 Sagia or other 3 lug bolt. I wish some one would make a run of super high quality super duty extended bolt face bolts. I want more power!. like 65,000 PSI power. :)
 
#19 ·
Thanks Im going to check that out. if I can get it to work with my trunion this my be the ticket for a couple things I have in mind I may just mke some thing simular. I assume it dove tails into a special trunion some how I need to get look as a GALIL.
The Valmet gas tube thingie is far too wide to notch into an ordinary AKM trunnion. The "ears" on the Valmet trunnion are wider apart than normal. Fortunately, the Yugo trunnion appears to be the same width; at least, there's room to cut the dovetails in a Yugo trunnion. I'm probably going to grind one side of one of my cheap jeweler's files and do it by hand rather than setting it up on the mill with a dovetail cutter.

I'll try to take a picture of the Galil tube and put it up.
 
#13 ·
As TRX said there was someone who made an ak with interchangeable barrels using a Uzi locknut and uzistyle trunnion. The barrels was in 9mm and 7.62x25.
Yea that was done by making a pressin adapter that held a flanged barrel and took a nut as I recall. It really wont work for what I have in mind as I need a bigger barrel shank for the bigger rifle caliburs and is not the best for accuracy. Its a great idea for the x25 and would give me a way to use smaller OD 30 cal blanks. Are there Uzi barrel nuts around cheap?? I have so many things going On the last thing I need is to start another project.
 
#15 ·
Barrelnuts at Numrich are at $16.20 so not cheap but you can make it your self. Somewhere I found a list on treads claiming it to be (UZI Carabine/ SMG 9mm 5/8x24) Cut and paste from the list so I don't know if it's accurate.
If its a stndard thread a addapter could be easly made to take them. the next isssue is that the RSB will not fit on a standard style build. but that could be modified. or ditched completly.
 
#16 ·
really all I need to do is find a sutiable thread to tread a trunion and then either by the tap or cut internal threads on my lathe. and thread the barrel to fit. a jam nut can be used and also tension on the threads allowing me to run a losser fitting thread.

Looking at the my Yugo trunions I do see that boring them out at all will cut into the lower rivet hole that across the trunion I can just plug it wit a tightly driven in pin and also do the same for the barrel pin hole.

this wold be a easy build on a milled threaded reciver If I could cut the barrel threads. but a milled will be harder to convert to 308 Win length mags. And obviously more expensive.

Im working on a interchangeable ejector tip as well I will likely also make it shoot every thing from 17 remington to 444 rimless marlin to possably 410 SG so with 4 bolts I cold shoot ay thing that flys or walks the planet on one reciver.

Its a shame You cant go from pistol to rifle and back again legaly. I still think that case needs to be fought in court if thompson won there is no reason a private individule cant win on the same precidents. Kind of pisses me of to be honest. the ATF apparently ignors court decisions and rulings on the law in there Opinion letters.

A switch barrel thaat went from pistol to rifle and back legaly would be really cool
 
#17 ·
Do you need me to take measurements of my Uzi locking nut? Its in the back of the safe...

I'm having second thoughts about the thread idea because the more I think about it, I wonder how are you going to thread the inside diameter of the trunion? I'm thinking you'll have to use a boring rod in the lathe chuck, and lock the trunion down on the tool post somehow to get it to reach.

What are your thoughts on my idea for a PK-style smooth barrel and locking wedge?
 
#21 ·
What are your thoughts on my idea for a PK-style smooth barrel and locking wedge?
Some vintage cars held various bits with taper pins. The pin stuck completely through the part and was threaded and held in place with a nut. To remove the pin, you just loosened the nut, whacked it with a mallet, and the pin fell out.

Taper pins and matching reamers are available easily. Cut some threads and rock on.
 
#18 ·
Can you post a link to his pic's. I tried to search for the PKM thread but came up empty. I proposed doing a vz-58 take down rifle to 1biggun before I saw his thread on the ak version.
The PKM idea sounds interesting. I was thinking of something on the order of an old savage 99 take down system.
 
#22 ·
Sorry I should have been more specific - not talking about a locking "wedge" rather a locking "dovetail" if you will. I found Ilya's pic in his Member Gallery:



Note the dovetailed locking "piece" that slides left-right. It mates to the notch on the barrel (barrel is silver in the pic). The barrel slides back to the stop and this piece locks it into the correct headspaced position.

The locking piece is supposed to be moved with the tip of a bullet (as it will probably be hot) and my thoughts are to add a long curved handle to one side of it so that you can pull down on the handle and since it is curved, it will force the wedge out sideways.
 
#23 ·
Do you need me to take measurements of my Uzi locking nut? Its in the back of the safe...

I'm having second thoughts about the thread idea because the more I think about it, I wonder how are you going to thread the inside diameter of the trunion? I'm thinking you'll have to use a boring rod in the lathe chuck, and lock the trunion down on the tool post somehow to get it to reach.
Im not looking to a UZI nut build at this time but if you ever have the gun out it would be nice to know the size and pitch.

there are Taps avaliable in the remington thread as well as the small ring mauser thread. so it could be just done that way. Internal threads are cut all the time in a lathe you turn the part and the boring bar goes on the carriage. and runs off the feed screw just like cutting external threads. It might be a little tricky getting the trunon set up in a 4 jaw but im sure it can be done. a jig might be able to be made to old the trunin on a rod that might help. it was done on the 500 S&W build on a 410 sagai with voids in the bore so i know it can be threaded.

the taperd pin wedge might be viable and I could run it through the old pin hole. the good thing about a tapered pin is as the threads wear from screwing and unscrewing the pin would still tighten the assembly together.

Right now my plan is a barrel nut like a savage bolt action and Im even looking into what threads the savage takes as the nuts are avalaible. I like how a jam nut pulls the threads tight and also has a bearing surface against the reciver. its not going to work with standard hand guards and getting a gas tube to clear might be a little tight, so Im not ruleing out any thing I was thinking of a cam lock set up as well were ecentric cam with a lever would latch into the face of the trunion some how.
likley to do this on a 23mm bore or bigger like Im Proposing is going to require some custom furniture it a jam nut is used, a normal threaded Ak barrel has a 1.175 flange so I know I can use a barrel nut with od of at least that big. Im planing to use a custom RSB so I can play with the max OD untill it starts hitting the carrier. Id kind of like to design it so it can be employed on a more traditional looking build as well
 
#24 ·
I have some taps coming. I have thought about this more and its occured to me thaat the barrel/jam nut does not need to be the same ID at the trunion. I can reduce the barrel ID and use like a 7/8" nut for the lock nut threads. This is a good thing as on a Remington take off barrel the profile gets pretty small in a hurry and by the time I cut off a 30-06 chamber and re chamber to another calibur there is not much area left for one inch threads especialy if you are going to use a barrel nut. 7/8 for the lock nut will allow the for the Gas tube to clear. Interestingly enough reloading dies use 7/8" thread and there are some pretty cool locking nuts for them knureled with set screws to lock them in place and would be perfect for this. One less part to make. there are also nuts made to to have a spaner wrench that can be used that can be foun ad bearing houses and other industrial places. that will not take up a lot of room allow for fore grips and RSBs to be utalized.

I am really thinking of Doing this to my 308 Saiga if It works on a standard gun a
A 300 WSM loaded light with a rebated case would really kick the crap out of a 308 WIn the 280 remington would be a perfect barrel to screw in as well and the brass already fits the bolt. It would be nice to have a heavy barrel 22-250 for varmit hunting a 243 for antalope and small deer and a 300 WSM for beat, and might aswell do a big bore for elephants, a shot gun barrel is not impossable either. sucks you cant make a rifle into a pistol or You could do short barrel sets as well all in the same giant case. OH well
 
#25 ·
I do not have the skill yet to open up the trunion on my lathe .Don't even have a four jaw chuck yet. But I have pondered using a three stone brake cylinder hone. They cost around ten dollars & are made for
3/4" -1" holes

Would there be an advantage to re-installing the barrel pin before boring & threading? just to fill the void. I thought of filing or dremiling most of the exposed pin in the bore before reaming/ honing.
Also thought of threading the barrel pin holes for set screws from both sides would be less meat cut from barrel.( Beowolf)
 
#27 ·
If you try the set screw idea, how about having the screws bear on a sliding pin, shaped to the contour of the barrel instead of directly onto the barrel itself.

Maybe even have a v-point on the contoured end and a hardened pin, so that the set-screw forces the point into the barrel as you tighten the set screw.
 
#28 ·
1biggun,

Rather than use a set-screw locking ring, check out Lyman's split-lock design: Lyman Split-Lock Die Locking Ring 7/8"-14 Thread - MidwayUSA
this is exactly what I have in mind there are other styles as well. the only concern is getting it tight enough to the trunion to keep the barrel locked. I can mill some flats on it so I can use a wrench as well. a pair of these is a option as well locked together

I got a pacakge today with some barrels so boys feast your eyes on these
the first is a aftermarket high dollar krieger (so Im told) barrel that has been fluted and also has a very cool break it is currently in 300 WIN mag and ill have to rechamber it it has remington 700 threads is very light. this is a very nice barrel its almost a shame to make it a 300 savage and Im contemplating making it a 308 or 300 wsm on a MY sagia 308, but for know its going on the kids build. there is not enough material to rechamber and keep the remington thread diamiter so we will see how it all plays out.


the other two barrels are Identical 260 remington factory SS barrels off of a model 7. the 7 is a light version of the 700 and these barrels are much lighter than a standard profile Remington 700 barrel bad for accuracy good for a 10 year old to carry (HE WILL CARRY HIS OWN RIFLE,MY RULES :) ). Interestingly the Gb will almost fit were it need to there will be very little work to profile this. the two AK style GBs are of of Saigas and are differant ODs and the L1A1 goes way back. Im wondering at what point i would have timing issues by moving the GB back. the further back the better balanced and easier to hande by a 10 year old. I also want adjustabe Gb so I can load light and shut of the gas, this is very important for teaching a kid to shot. plinker loads untill its game time. any way a little eye candy there is $350 worth of barrels here a really good deal IMOO . Im thinking stainless reciver BTW :)
 

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#29 ·
I do not have the skill yet to open up the trunion on my lathe .Don't even have a four jaw chuck yet. But I have pondered using a three stone brake cylinder hone. They cost around ten dollars & are made for
3/4" -1" holes

Would there be an advantage to re-installing the barrel pin before boring & threading? just to fill the void. I thought of filing or dremiling most of the exposed pin in the bore before reaming/ honing.
Also thought of threading the barrel pin holes for set screws from both sides would be less meat cut from barrel.( Beowolf)
I plan on boring in a mill and then using the same set up and chuking in a tap. a four jaw would of course work. a drill bit would possably work also.

But try this on I was saving it so my idea didnt get stolen, but since you asked. I happend to notice on my drill and tap guide poster that 22mm or .8661 is percisly the correct size for a M24x2,00 metric thread. BINGO!!! a AK 74 trunion is 22mm correct??? I know the Saiga trunion i have here is 22mm :) no drilling,boring or cutting. TA DAA :) You heard it here first :) the dies and tap are standard. I have no idea if they will hold up to the bolt thrust but they will work. the Sagia trunion I have is really light. I do know that Willie threaded his 410 Saiga in his 500 S&W conversion and it had voids fro the rivets and a barrel pin hole ect. the Saiga trunion I have is super light compared to the Yugo and may not be ideal for a 308, 260 or other heavy calibur build but would be perfect for 223, 5,45. 7.62x39 7.62x25 beowulf, socom ect and likley the 300 savage loaded slightly light. for a youth gun it may be the way I go. Im going to get a bunch of parts on the bench and then he and I will decide what he gets. Im still looking for a cheap 5,45 bolt or two. I should have bought him a AK 74 kit and sold off the AMD donner kit. Im starting to get excited about this build. may do a light weight youth build and a heavy duty high pressure build based on my 308 Saiga action

Im not sure if its worth putting a pin in or not to thread Id be worried it might move and gall the threads or something.

If I get this all ironed out and it goes well im considering offering a trunion threading service t off set the tooling costs. Im still liking the 1-1/16-16 remington 700 threads on Yugo for the 260,308, 243 ect evenif loaded light. It will of course work on lighter caliburs.

Im thinking a 16" superlight x39 with a heavy x39 target/snipper barrel set on a standard kit would be the cats ass. might be able to get a 223 to work in the same mag well with some work
 

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#30 ·
Ill cut a couple of these aluminum super light G3 mags down to 3 or 4 shot hunting mags and of course a few full size for target practice. He will likley not see Semi auto for a few more years at least not while hunting.

I got a guy who is susposed to be a master at carbon fiber thinking about a pistolgrip stock and fore end BTW. the problem with light is the recoil so Im going to have to balance what he can carry and hold up with what he can handel recoil wise. I may add weight for target shooting and take it out for hunting, Untill I see how effective the breakis on a 300 savage I wont know. I havent rulled out a 243 or any calibur yet except likley the X39
 

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