AK-XCR Lower Build Log 2023

712 Views 10 Replies 5 Participants Last post by Holdaway, 2 mo ago

Chowwow

Discussion Starter · 2 mo ago

Regarding the Poll:

Link to Reddit thread of poll

CMMG Mag Release

A steel version of the mag release used in CMMG's Mk47 line of 7.62x39 rifles

Existing design from a large company
Long enough for the Lower w/ AR trigger

Must be remade in steel to account for steel magazines
Thickness of release will result in trigger hole being shortened as seen on the CMMG Mk47 line

Custom Mag Release

A customized mag release inspired by the CMMG mag release design but thinner
+ Long enough for the Lower w/ AR trigger while not hampering the classic trigger design of the XCR
- Proprietary part made by a single machinist somewhere

AK Mag Release

Reuse the mag release commonly used in the AK-47 line of rifles
+ Cheaper and available

Parts in varying quality, difficult to ensure compatibility
Most likely too short to be used in the Lower w/ AR trigger

This thread will be the build log for the AK-XCR lower project. The previous thread will remain as a poll to guide the direction of new projects in the future, the first few pages of the poll include initial musings of the project however.

The following images reflect the current state of the project.

First 3D print mounted to Standard upper:

Trigger Air gun Wood Gun barrel Gun accessory

Trigger Air gun Gun barrel Gun accessory Machine gun

Wood Gun accessory Everyday carry Metal Fashion accessory

Latest version of the CAD model, with CMMG mag release and AK magazine to aid in design.

Gun barrel Automotive window part Map Trigger Auto part

The goal of this project is to produce two CAD models of the AK-XCR; one that uses the XCR trigger and a taller one that uses an AR-15 trigger group. Actual production is to be focused on the AK-XCR w/ AR FCG when it's time to put endmill to metal. Development is slowed due to the final stages of the AR-XCR-L project. It's hoped to have a complete lower built by the end of this year.

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Sean K.

· #2 · 2 mo ago

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.

And AK mag release would be great....I just dont' think it's all that adaptable to the XCR platform.

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Sean K.

· #4 · 2 mo ago

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)?

While it would awesome to me to use a rock and lock AK mag b/c they are cheap, readily available and uber reliable.....they may not be as easy a match to this particular platform's controls as a Bren2 X39 mag.....

Just something to consider.

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Sean K.

· #6 · 2 mo ago (Edited)

Chowwow said:
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.
View attachment 16203

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.

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?

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.

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.

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.

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.

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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Sean K.

· #10 · 2 mo ago

Chowwow said:
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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.

Makes sense.

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What kind of magazine release do you prefer?

CMMG Mag Release

Custom Mag Release

AK Mag Release

AK-XCR Lower Build Log 2023

Chowwow

Sean K.

Sean K.

Sean K.

Sean K.

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