Welcome to the mess of dimensions found with 5.56 AKs. Why everybody didn't simply build to AK-74 dimensions is beyond me.

The first thing I thought when you said you wanted a 3rd burst (and I know you have the FFL to do it) was to use a Tantal receiver and trigger group... So you already have that part right. But an even easier option is to get a Beryl Archer and make the necessary mods to the receiver to accept the Tantal group and controls. The Archer is already set up for the correct Polish safety and left side mode selector. At worst you might have to drill the 3rd pin hole, slot the rail, and maybe weld the sear ramp onto the carrier if it's been machined off - I don't have an Archer so I can't confirm any of those things.

If you insist on using the Tantal parts kit and receiver you may have to go a different direction than you're going with the parts you have in hand.  Here are the problems I see with your kit:

- Tantal uses an AK-74 type 22MM trunnion set up for long lug bolt.  The 23mm barrel you have is set up for a short lug AKM bolt which is what Bulgarian 5.56 rifles use. Not only do you have to turn down the barrel chamber journal to 22mm but you will have to set it further back into the trunnion to headspace it. This can mess with things like the handguard retainer slot and the gas port if they are already machined/drilled.

- The WBP bolt is not compatible with the trunnion or the Tantal carrier at all. Incorrect lug length and the camming ramp on the Tantal carrier will start it into rotation at the wrong position.  Not going to work.

Your best bet IMO is to source an AK-74 5.56 bolt such as for a Saiga or a Beryl - also there was a guy on AKFiles that was making new billet 5.56 stripped bolts of this type. I don't know if he's still there but take a look. These bolts would accept AK-74 extractor and firing pin. Modding the firing pin to accept a spring is not hard, but in my experience it's not needed. I haven't had any slamfire in thousands of rounds of shooting unsprung 5.56 bolts, but I almost exclusively shoot Wolf .223 which probably has harder primers. The commercial .223 I've fired has had no issues either but I haven't used a lot of it.

You can also simply do what many of us have done on AK-74 5.56 bolts and modfiy the Tantal bolt. An unmodified 5.45 bolt will cycle 5.56 just fine but you need to adjust the extractor for best function. What you do is remove the extractor and find the flat inner shelf that contacts the bolt head - this shelf acts as a stop surface. You want to modify the extractor so that it pivots further towards the center of the bolt face. File down the shelf a bit at a time until the bolt /w extractor installed holds a 5.56 case tightly enough that it will not fall out while holding the bolt upside down, but loose enough that you can rotate the case by hand (with some light friction) while it's inserted into the bolt /w extractor installed.  This mod also pushes the 5.56 case towards the ejector claw, and without this mod if the ejector is too short you can have cycling issues and possibly even damage the ejector claw.

For the barrel I would suggest looking at the Arms of America 5.56 AK-74 nitride barrel. This will go right into the Tantal trunnion and will have the correct setback for the trunnion/bolt lugs. These are great barrels and in my experience very accurate - will do a little under 1MOA with quality ammo and the right headspacing.

The AoA AK-74 barrel will work with the WBP combo gas block (I have one of these waiting to build when I finally have time) but I don't know about many others.

For magazines you will be able to use a couple different types but the most readily available are Beryl, Circle 10, and I recently started using the AC Unity 5.56 mags which are very nice.

DO NOT USE 5.45 GAS PORT SIZE!!! It will be horrendously overgassed - 5.56 chamber pressure is on average something like 15k PSI higher than 5.45.. I used a 1/16" (.0625") bit which comes out to the same port size as a carbine length 16" AR. This gives a nice soft recoil pulse like you would expect from an AK-74 type rifle.

well I'm not gonna follow that chunk of logic with much, except, you might consider using the Galil bolt and carrier. It has the thicker stem and may help with longevity? I dunno, looks more stout.

ETA: I did use all Bulgarian 74 parts to build up a barreled Saiga receiver once in 5.56. Worked like a charm. Mine was weird though as the Circle 10 mags wouldn't work, only the Galil mags did.

I think that is Cerephim.

Galil uses an AKM dimensional bolt and carrier so it won't work with the Tantal trunnion

The Saiga .223 is weird in that it uses a thin stem bolt/carrier like an AK-74 but the trunnion and mag well are set up for AKM dimensional magazines. Which is why the Galil mags will fit and some other mags e.g. Circle 10 or Beryl have to be modified slightly to fit.

Iirc this has to do with the Russian domestic requirement that sporting rifles not readily accept military magazines. Whereas the military variant of AK-101 has "normal" AK-74 mag well dimensions and works with magazines like the Beryl and C10

AK Builder has them in stock right now

https://ak-builder.com/index.php?dispatch=products.view&product_id=30804

ETA WELL SHIT no they don't.
I wanted to buy another bbl so I will be asking them as well


Contact them about the 5.56 Tantal barrel as well - I forgot they offered these

https://ak-builder.com/index.php?dispatch=products.view&product_id=30888

I swear mancat, the amount of knowledge you share is amazing

Shit I don't know it all I just spent a lot of time figuring out all the differences on 5.56 AKs.. I'd own them all if I had the safe space

If you use an AKM trunnion yes it could work with the barrel, Galil bolt and carrier. Not sure if the AKM bullet guide will work with 5.56. You may have better luck there using a Bulgarian 5.56 trunnion as it will include the correct bullet guide, and the lower height of the locking lugs is correct to use mags like Circle 10 or Beryl. A normal AKM trunnion has locking lugs that protrude too low down and they will prevent those mags from pivoting in - the area forward of the feed lips will contact the bottom of the locking lugs.

Using an AKM spec bolt with the Tantal receiver - not sure if there will be issues with the ejector claw. If you already have the bolt and carrier just put it into the receiver and check if the bolt even fits past the ejector  and if it does, does the ejector reach all the way into the bolt face

finally found the pic of my .556 build. Disregard the airsoft GP-30

Great thread!

@nictra nice 101 look to West Papua for inspiration
@Manticore_arms You could contact Two Rivers for some build advise, I know they put together a similar thing to what you might have to do. A Hungarian 5.56 underfolder clone built around an AKM trunnion, bolt carrier, Bulg bolt+23mm barrel with a AK74 reciever, they tuned it to run w wieger mags. I wondered what the deal was on those new Pole 5.56 parts seems like a huge oversight but then the Polish companies have a strong history of not communicating well.
Well I see where most of the knowledge base has gone. I was wondering where the mythical @mancat went, tis logical since I suppose this place has alway been ye exile de camp. The yunglings are everymanning on redd und ig. The last year has felt like being in the wilds. Its a good thing I decided to drink the retroAR coolaid. A similar build idea has been bouncing around in my head since imports are dying.
Thanks ATF and shady importers
https://www.youtube.com/watch?v=uGd-dbFS_wQ

hahaha.. you came from the saiga forum or akfiles?

Neither but its still dying, Im actually still active on there but not nearly as much. AK stuff is getting boring because of import halts and kit drought. People using them as investment assests is driving away new-young blood who cant afford to pay a thousand for a starter AK. At least some acceptible 7.62 examples are being made in the US now. Ks are meant to be cheap and accessible! Im getting back into retro 16s now which are safer from Barris EAs. Luv my AKs but the only things that interest me now are really unique costly build projects, one similar to above prospect.