AK-XCR Lower Build Log 2023

Results of Reddit Poll. FYI: I had to vote on one of them to view the results. I voted for custom mag release expecting it to be unpopular.


I always count these results as they would on here. In this case the results are almost evenly split. If only people really knew how hard it was to get an AK mag release to work; I might just throw out that result due to design considerations.

Sean K. said:

If you're having to have a CMMG release made in steel.....then it's going to be the same deal as the 2nd option. Custom, proprietary and made by a single machinist.

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I'm starting to think it's unavoidable; unlike the BHO on the AR-XCR that could be supplemented with a 3D printed extender, I'm going to have to figure out how to source these parts. You don't suppose a 3D printed mag release will suffice?

Sean K. said:

I would think the bigger problem is that where the AK mag release resides is the same real estate as the BHO on the XCR. Which reframes the discussion point: what is the primary purpose of an AK dedicated lower? Is it to use AK mags (including metal ones) or is it to reliably feed X39 from something other than a STANAG pattern (like ASC, CProducts, etc)?

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It's solely to take advantage of the AK magazine and specifically to service the crowd that was excited for abran007's lower design. Something like that should persist somewhere. I'd love to include the XCR BHO into the lower but from what I understand from every AK mag I've gotten, there's no way for a BHO to work with those mags unless I get really creative with an exclusive BHO system. Considering how low profile the AK mag allows, I think it works the slickest with the XCR trigger group; together the package is very lean and light. To get the most features though, you'd need the AR trigger group. Otherwise, I'm not too interested in the x39 round itself and I can't think of any other features to include with it in the constrained package as is. I'm open to ideas though.

Sean K. said:

If the 3D part was sintered metal...maybe. I don't think those machines have come down in price to make them affordable yet though....And I don't think a printed plastic one is going to hold up.

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I'll do one print as a prototype either way. Worth a look.

Sean K. said:

I'd highly recommend you do this simple test: Go to Home Depot. Buy a concrete cinder block for $1.08....the 2 chamber 8x16" kind. Take a .556 XCR, shoot one chamber at 15-20 feet. Now shoot the other chamber with a x39 gun. That usually sells most people on the round.

X39 is basically a hotter, supersonic .300 BLK.....for cheap.

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I certainly will blow up some concrete on video for this demo.

Sean K. said:

I dunno....I find working with AKs, I don't really care about BHO that stays open when the mag is removed. I do use Yugo mags b/c they lock back on an empty chamber....b/c you can feel the gun run dry and I run other metal AK mags with the BHO followers from Weapon Tech for the same reason. That said, the only reason not having BHO available on an AK is b/c it's an old ass system and there's not really a good way to implement it. For a modern gun though....it's sort of expected.

The more the project is discussed, the more it seems to me that the Bren2 X39 mags make more sense in this particular platform (if the purpose was solely to get a good, reliable mag to work with X39 in the XCR...that said though, it would seem ASC/CProducts/Duramags all have improved function to the point of being pretty reliable in the XCR or ARs so maybe the point is moot). While the XCR is AK-like in terms of it's bolt and gas system; it's not an AK.

That said, if there were an XCR lower that took AK mags (or Bren2 ones) and ran reliably, I'd buy it; BHO or not.

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I need to get a Yugo mag to see if it'll work on the AK-XCR; it might be just the ticket. Otherwise, I don't know how to install a BHO device at such a small space; AK mags just were not designed for LRBHO.

The Bren 2 mags may be fairly easy to implement. Challenges include finding the dimensions of the mag well for the CZ Bren 2 and determining if the mag is compatible with the XCR mag catch arm (God forbid I have to make ANOTHER proprietary part for a lower project). After this project, I'll look into it and see if it's low enough hanging fruit to grab at. The issue with the Bren2 project has been it's been polled to be relatively unpopular and I need to stay focused on one project at a time for the best results. Those Bren2 mags are also proprietary and harder for people to get. The community will need to come together to discuss what they'd like next, probably after they see the AK-XCR. Enthusiasm was quite high at the time when abran007 was building his, but we are all older and wiser now.

Sean K. said:

Is this lower going to be a picatinny rail as well or standard XCR stock/brace (not that we know which way the political winds will blow right now on 'pistol braces')?

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Rear 1913 rail all the way. To me it's the new standard and in the case of the XCR, looks very neat and versatile. It's also easier for me to machine than the XCR's stock slot and ensures there is enough material in the lower so that it's robust. I may design a QD sling point into the lower when I get the chance; maybe under the rail or in the middle of it. I need some experience with designing the QD hole first.

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abran007 said:

LRBHO is possible with AK mags… you just have to change how you look at the problem. I haven’t worked it out in reality but I have the idea on paper. Shoot me a message if you’d like some ideas, I’m too busy with work to mess with it right now unfortunately.

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I've been ruminating about the LRBHO that abran007 proposed and still need to ruminate some more. It's interesting if it works and I'll go over the idea here when I have permission to. My concern is that using the XCR BHO arm would occupy the space where the AK style mag release should be and I'm having trouble reconciling both features when they are on top of each other like that. More to come.

I was looking at the CZ Bren 2 AK lower from Lingle Industries the other day, knowing what they did for the Bren 2 was similar to what I'm trying to do with the XCR-L. I inquired about the mag release they used and they said it's actually an AK mag release, the extended mag release from RAM Tactical to be precise.


It's hard to tell from photos, but it looks like that if Lingle could make a lower with an AR trigger group and AK mag release for the Bren 2, I could be able to do the same with the XCR. It would be damn great to not have to make a new mag release and the steel AK releases should do great with AK mags, if I could get them to fit on my lower.


There is still some distortion with the trigger guard due to the placement of the mag release, but at least it's not the trigger hole being squished small like the CMMG MK47. I'll have to buy some of these mag releases when I get more time to work on this idea. If I can get the AK releases to work (the RAM Tactical version in particular) I may choose to sacrifice the trigger guard shape in order to use hardware that works and isn't proprietary to make it easier on myself when manufacturing.