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Thread: BIZON Conversion done. Need help with posting pics

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    Gunco Member jungp's Avatar
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    Default BIZON Conversion done. With Pictures.

    Hi Folks:

    My wife and children were gone for four days last week. So I decided to tackle this project while I had time for myself. I must give credit to the following people on this board for information and inspiration: JPGlee1, Pookie, KernelKrink and VIS.

    Equipments: Harbor freight 7x20 lathe, hacksaw, drill press, tap and die, caliber, grinder, dremel, and belt sander (and shop vac)
    Materials: Whatever was at my reach plus OOW '74 receiver, Bulgarian '74 bolt and carrier, FAL flash hider, UZI barrel, K-VAR stock and grip, 4 sten mags of various origin, Bulgarian rear tang.

    1. Front trunnion. I made this out of 1 inch thick 6061 block. Drilled .625 hole for barrel and .700 hole for the carrier. The trunnion is also the rear sight housing. 4 hours.

    2. Turn the barrel to .625 and press fit into the front trunion. 1 hour

    3. Modified the bolt and carrier. Bolt carrier is heat treated. I could not drill or file. I cut the handle with dremel and moved back 1 inch and welded on. Since I could not drill into the carrier, I went ahead and welded the bolt to the carrier. Trim off the rear safety lug. 4 hours

    4. Sten mag housing. Made this from 1.5 inch wide flat steel and 1.5 inch wide 90 degree angle (not sure what to call it) that I got from home depot. The hardest part was the mag release. Took three tries to get the right height. Even then, I have to push the magazine slightly upward before I can press the release. Need new design but it will work now. 3 hours.

    5. Trimmed 1.5 inch from the front of the receiver. This was a mistake. I will explain it later. Recut the bolt release on the top left rail.

    6. Put it all together. It doesn't work! Hammer does not hit the firing pin. Also, the bolt will stay back when you pull the bolt all the way back. This is because the bolt is now 1 inch shorter and will not hold the hammer down.

    7. Modified the hammer to have different angle to strike the firing pin. Also smooth out the top of the hammer so it won't hold back the bolt.

    8. Modified the single hook trigger. Welded small bead on the inside of the hook. So the hammer is held down little lower.

    9. Shorten the cover and put it all together. Safety does not line up with the the cover.

    10. Made front sight base fron 1 inch thick 2021 alumninum. Drilled 5/8 inch hole (.625) for the barrel. The base is secured by 2 8x32 socket head screws for now. Need to pin it later. I bought some front sight inserts fron TAPCO but could not find any tap will match that. So on my handy dandy lathe, I made that had 10x32 thread. Front sight adjustment is only vertical. (2 hours)

    11. Made rear peep out of 2021 alumninum. The hole is 3/16 wide. Bottom part is drilled and tapped with 8x32. Two socket head screws pull from either side for horizontal adjusment. (1 hour)

    12. I had STG-58 flash hider. I wanted to thread the barrel but I just could not do it. At 200 RPM, it was hard to index the lathe. I think there is info on the web how to modified this lathe to go 60 RPM. Maybe later. Instead, turned the diameter down to .585 and slip fit then use the 6x48 screw to secure it. (3 hours wasted trying to turn thread).

    Lessons learned. It may work better if both front and rear part of the receiver was shortened. The trigger modification may not be needed if the bolt does not travel the same length as the '74

    I do have another set of stock ('74 S type folding stock)/bolt/carrier/barrel/receiver. Not sure if I will have time to work on it.

    Function tested with dummies and it failed to eject full length cartridge. It will eject an empty fine. Had to shorten the ejector tiny bit. Like I said, this may not have been a problem if the receiver of shortened from the rear also.

    I don't have any feed rail. The magazine is tilted back a little bit because it is 90 degree to the bottom side of the receiver not the top. So, the cartridge points up ward in a correct angle. I had not had any stove piping while running dummys.

    I drew up a quick dimension for the front trunnion blank and took it to local shop. It would cost about $20.00 for 1112 steel at quantity 1000. Much more for 4130. It is possible that I can set up for a group buy but it would take 90 days. Not sure if shot has drill size .685. Otherwise, the hole will be .625 (5/8 inch) and have to turn down the barrel.

    One more thing I would like to point out is the head spacing issue. The best way to address this would be deepen the chamber about .05 so the cartridge is completely supported. If no chamber reamer is available, deepen the bolt face.

    I forgot to mention of about the front handguard. Made from 2 3/4 inch thick oak veniers sandwiched together (1 hour).

    Pictures are in. Thanks everyone on help how to post pics

    I will have to wait until this saturday to go out to my ranch to test it out. If I have time, I will do quick test and right up a report on it.


    Front View

    Side View

    Mag Well for Sten Magazine

    Welded AK-74 Bolt

    View From the Rear Peep Sight

    Modified Trigger to hold down the hammer
    Last edited by jungp; 04-19-2005 at 08:53 AM.

  2. #2
    BANNED vegeta's Avatar
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    somebody hurry up and post these I want to see them!

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    RIP Sangrun Hunter's Avatar
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    You can always use our image host www.picyard.com and we can help you post them.

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    BANNED jpglee1's Avatar
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    ". Modified the bolt and carrier. Bolt carrier is heat treated. I could not drill or file. I cut the handle with dremel and moved back 1 inch and welded on. Since I could not drill into the carrier, I went ahead and welded the bolt to the carrier. Trim off the rear safety lug. 4 hours"

    UMMMM...thats gonna be a true bitch when it comes time to replace your firing pin or extractor....You CAN temper the carrier to work on it then re-harden it, thats what I did No worries. I would suggest that you mill a hole down thry the carrier from the top now to allow you to drive the firing pin retainer out. You should have enough room to get the extractor if you clearance the carrier right. It took me about 2 weeks to get my head wrapped around this problem. If you look at my pics you can see how I did it...I modified the carrier w/a new slot and modded the bolt/carrier to allow them to stay locked together in operation but still be seperable to maintain them. the rails keep the bolt from rotating, my custom carrier slot along with the mods to the bolt head allow the bolt/carrier to be in constant contact in forward or reverse action... I wish I could take better pics of it, sorry

    FWIW ALL work done to my bolt/carrier was done w/a MIG and a makita w/80grit sanding disk and jewelers files, with lotsa coffee to steady my hands I MIG'd the material on until it was enough to allow me to shape it back to final shape w/the sanding disk and files. I went old skool on it....I could have used a Oxy Acetylene welding setup just as easy. My whole entire build can be done in a SMALL shop with basic tools..... NO lathe


    http://www.gunco.net/forums/showthre...d=1#post100864 My PICS

    Right on man...your shite sounds awesome. Im almost done with mine too. I put the rails in yesterday, heat treated the holes and did the trigger guard (no pic of the guard yet)...... I also started on my recoil spring/guide. Im using a standard AK recoil spring, full length with a 5/16" guide rod up the center. the rod runs all the way thru the carrier....

    The problems you have sound similar to mine. I shortened the receiver to the REAR side, and made sure the magwell was all the way forward. Generally I tried to keep the trunnion/BBL in about the "original" position. This gives me about the same bolt travel as before, nice and cushy when it ejects hopefully. I had to add 1" to the back of the bolt so it would cock the hammer instead of the bolt tail (which will wear out)... I also did extensive bolt mods. I ended up putting my ejector about 2/3 the way back in relation to the mag feed lips. You wanna keep the rounds pushed down w/the bolt as it is ejecting, you dont want it to eject when the bolt is clear of the magazine, it will cause issues. I studied 3 of my 9mm/762x25 handguns to get an idea of where the ejector typically would be located. First time I welded the rail in the ejector was 1/8" too far forward and wouldnt let a loaded 9mm FMJ clear to eject. I moved it back, no sweat. My rails are spaced .250" from the uppers (used a 1/4" drill bit, worked aswesome)and are located approx 3/4" closer to the front of the receiver than an AK is. I use the rails to help keep the bolt head from rotating. In my setup the bolt head is 100% supported during its cycle so it cannot rotate outta locked position (in the carrier, the bolt doesnt lock to the trunnion)I had to mod the bolt/push lips heavily to make it all work out right, I also had to relocate the charging handle back approx 1.5" on the carrier. It would be VERY easy to use the snout of the carrier as a sorta ambidextrous cocking button, where you push it backwards to cycle the action, on this one Im using a right side charge handle, but I might try a snout charger next time.....

    Im not trying to hijack, sorry... Im stoked you got yours done... Lets see it


    No problem on the help, I like to share the love. Especially for CALI boyz that want to do their own thing legally.... Much love bro, keep it in the 10ring!!!
    Last edited by jpglee1; 04-18-2005 at 02:57 PM.

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    BANNED jpglee1's Avatar
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    " drew up a quick dimension for the front trunnion blank and took it to local shop. It would cost about $20.00 for 1112 steel at quantity 1000. Much more for 4130. It is possible that I can set up for a group buy but it would take 90 days. Not sure if shot has drill size .685. Otherwise, the hole will be .625 (5/8 inch) and have to turn down the barrel."

    I wouldnt have them drill it anyway...have them use a 5/8" drill then REAM it up to .675"(my UZI BBL is .675" not .685?)Reams are cheap...I would do a single .675" hole and leave the 5/8" part un supported. Simpler to build that way. Remember the UZI doesnt even have a ring supporting the chamber end (well some dont...some do, its not essential) ALSO remember that a STEN uses nothing more than 2 pieces of 1/8" steel pressed into washers for a trunnion. Dont over think it, it doesnt have to be super heavy. Infact, you could EASILY use 6061 or 7075-T6 aluminum instead of steel. It would hold the pressure just fine (the BBL itself will hold ALL the pressure on its own, the trunny is simply to locate it)my trunnion is just 2 pieces of 1/8" steel w/holes in them the right size w/the BBL MIG welded to them, it works fine....

    Have you tried www.emachineshop.com for having them made? I can use the software fairly well now, I can do a simple block trunnion if you want to. In aluminum it would be fairly inexpensive me thinks, surely a lot less than the quote you received from your shop.... Im guessing approx $7-8 bucks a unit for 500.... $35 or so for a single unit...keep it simple. Make a basic block 1.25" wide x 1.00" tall x 1.75" long with a single .675hole reamed thru it. Use a .005" interference press fit. Probably wouldnt even need a locating pin if you use enough press-fit. Its just a 9mm afterall. I personally would like to see a trunnion like the Mech-Tech carbines use, where the BBL is held in with cross bolts pinching the trunnion together. mill slots in the bottom of the BBL to locate it/keep it from turning..... Theres lotsa ways to do it....Heck like someone else said you could make it caliber swappable if you made the left rail screw in and out and started with a 762x39...Make the 2nd trunnion screw in/out and use a magwell adaptor made from a MAC-11 magwell welded to an AK magbody (5rd)then when you wann go 9mm you swap trunnions, left rails and click in the magazine/magwell adaptor. I think it would work awesome



    OK IM done. sorry

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    Gunco Member Fargo's Avatar
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    Gunco Member jungp's Avatar
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    Thanks everyone for helping me post pics. Sorry that I couldn't get any sooner.

    Few more notes on magazines. I think it might work better using two column type mags. For my second build, I will try Suomi mags. I have four sten mags right now. Two from Tapco which are made in Finland. These are blued and they seemed feed well. The other two are from CDNN which are parkerized. Not sure but the parkerizing increases the friction inside of the magwell and they do not push the cartridges fast enough.

    Another reason is that Sten mags are very hard load. Since all I have to do is to manufacture new magwell and release, I will try that in few weeks for Suomi type. No time for it next weeks since I need to start working at the ranch. Two jobs and a family ties me down pretty well.

    If you have any question, just PM me.

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    Vis
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    I'm speechless
    AK-47 user and abuser since 1980.
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    RIP Sangrun Hunter's Avatar
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    Very cool! That thing would look awesome with a side folder too.

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    Gunco Member jungp's Avatar
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    Yes. I do have Bulgarian side folder and rear trunnion. I just did not have enough time. Also, I haven't figured out where to properly install the front latch on the shorter receiver. Looking at the many Bizon pics, I think it is on the rear sight base. Next build.

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