Mk 18 Question

[Solaran_X]

So I got my 10.3" Daniel Defense barrel on order (which is apparently proper for clone of the Mk 18, since both Colt and DD barrels were used by Crane to build them). But I have a question.

Looking at the Mk 18 thread on AR15.com, I see that the Mk 18 Mod 0 used a A1 lower while the M4A1 CQBR Block I and II (often called Mk 18 Mod 1 incorrectly) use a A2 lower.

What is the difference between the A1 lower and A2 lower? Is it just the pin size used for the FCG and the front pivot? Or is there something else as well?

[Nate7667]

The FCG and take-down pins are all the same from A1 to A2.
The main difference is the re-enforced area at the buffer tube extension and front pivot pin.
The A1 was marked "Auto" and the A2 is marked "Burst". There are some rare cases where some A2 have been marked "Auto". There was just one sold i think on Sturmgewehr recently.

[JoshIronshaft]

If you google "A1 vs A2 lower" there are a ton of arfcom threads but more interesting is in the images there are three pictures that show some differences in the reinforcements.

[Solaran_X]

So apparently my LE6920 (2012) and MT6700 (2000) are both A2 lowers. Kind of puts a damper on my Mk 18 Mod 0 clone project (uses A1 lower), but I could still go with a M4A1 CQBR Block I or II.

[NathanB]

I don't think anyone is going to knock you for making a copy with a different lower. I get the whole like the pros use thing but that's so minor

[Solaran_X]

I don't think anyone is going to knock you for making a copy with a different lower. I get the whole like the pros use thing but that's so minor

True. Cause real Mk 18 Mod 0s and M4A1 CQBRs are full automatic...and the ones we can make (affordably) aren't. Same with my Mk 12 Mod 1 I just picked up a MT6700 to use as the base rifle.

[Nate7667]

Buy a NoDak Spud retro and build and engrave it with all proper markings. There will be some NDS markings on it but still the correct looking receiver.
Or try to find an 80% A1 lower and have it engraved with the proper markings. Not sure i've ever seen an A1 80% for sale, but then again ive never looked.

[Solaran_X]

Buy a NoDak Spud retro and build and engrave it with all proper markings. There will be some NDS markings on it but still the correct looking receiver.
Or try to find an 80% A1 lower and have it engraved with the proper markings. Not sure i've ever seen an A1 80% for sale, but then again ive never looked.

Or I'll just build a M4A1 CQBR Block I, which uses pretty much the exact same setup as a Mk 18 Mod 1 - just on an A2 receiver. Especially since my LE6920 is already registered as a SBR.

[Nate7667]

Even easier and already have the stamp.
Just wasnt sure how particular you were looking to get.

Some of the parts of unobtainium are so hard or expensive to get, to me a simple "close enough CQBR" is good enough for me. But im not a purist either.

I just used a DD MK18 upper, Surefire 556RC, T1, DBAL-i2, B5 Sopmod, all on an Aero Prec PewPewPew lower and tossed in a post-sample DIAS to take advantage of the markings lol

[Solaran_X]

Even easier and already have the stamp.
Just wasnt sure how particular you were looking to get.

Some of the parts of unobtainium are so hard or expensive to get, to me a simple "close enough CQBR" is good enough for me. But im not a purist either.

I just used a DD MK18 upper, Surefire 556RC, T1, DBAL-i2, B5 Sopmod, all on an Aero Prec PewPewPew lower and tossed in a post-sample DIAS to take advantage of the markings lol

Damn you class VII people!