Converted Colt LE6920 to Mk18; what do I need to know?

[okie]

I took a stock LE6920 and sent the barrel to ADCO to have it cut to 10.3" and they enlarged the gas port to Crane spec while they were at it (for no additional charge, thanks guys!).

I took out the H buffer and replaced it with a Colt H2 buffer. Left the stock recoil spring.

I switched the trigger to a Geisselle (I can't remember which one it is, but it's the semi version of the NSN one that was approved by Crane).

Instead of reinstalling the A2 flash hider, I used a Smith vortex so I could use a direct thread suppressor with it.

Other than that, I haven't changed anything internal. I put on a RIS and a Crane stock, as well as an Ergo grip, but that's it.

I shot 100 rounds through it the other day, M855 and Tulammo. The Tulammo was too weak to lock back on certain mags, but that's to be expected. The next time I shoot steel I'll just switch back to the H buffer.

Is there anything else I need to change? I think it has Colt's newest extractor spring, and it seemed to be ejecting in the right direction. It's about a 2014 production I think. It was one of the Mexican overruns, and it was so nice I decided to keep it as my main AR and register it.

[everready73]

Sounds good to me. Seems to be running like it should.

When I read the thread title gas port size was the first thing that popped in my head but they took it to .070 which is optimal for mixed use and that barrel imo.

I wouldn't change anything

[hotrodder636]

Sounds good. Let’s see some pictures.

[okie]

Sounds good to me. Seems to be running like it should.

When I read the thread title gas port size was the first thing that popped in my head but they took it to .070 which is optimal for mixed use and that barrel imo.

I wouldn't change anything

Yea I figured Crane probably knew what they were doing by now. It might be a little gassy with NATO spec ammo, but that's probably not a bad thing.

[MistWolf]

The only thing I would have done differently is left the original port size alone and run the upper 100% suppressed. Sounds nicely done. Let's see what she looks like!

[chef8489]

you get your tax stamp back for it and if so congrats.

[JulyAZ]

you get your tax stamp back for it and if so congrats.

Found the fed.

What Mk18 are you building? I know you mentioned a Ris, but is it the drop in KAC RIS, or the Daniel Defense RIS II? What you needa do really depends on which version of the CQBR you’re building.


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[davidjinks]

I did the exact same thing for my first SBR. Add an H3 buffer and call it a day.

I experimented with the A5, H, H2, H3 buffers/system and a whole mess of different types of buffer springs. The best combination, for me, was a standard Colt spring and H3 buffer. Smooth recoil, solid ejection, no functional issues.

I took a stock LE6920 and sent the barrel to ADCO to have it cut to 10.3" and they enlarged the gas port to Crane spec while they were at it (for no additional charge, thanks guys!).

I took out the H buffer and replaced it with a Colt H2 buffer. Left the stock recoil spring.

I switched the trigger to a Geisselle (I can't remember which one it is, but it's the semi version of the NSN one that was approved by Crane).

Instead of reinstalling the A2 flash hider, I used a Smith vortex so I could use a direct thread suppressor with it.

Other than that, I haven't changed anything internal. I put on a RIS and a Crane stock, as well as an Ergo grip, but that's it.

I shot 100 rounds through it the other day, M855 and Tulammo. The Tulammo was too weak to lock back on certain mags, but that's to be expected. The next time I shoot steel I'll just switch back to the H buffer.

Is there anything else I need to change? I think it has Colt's newest extractor spring, and it seemed to be ejecting in the right direction. It's about a 2014 production I think. It was one of the Mexican overruns, and it was so nice I decided to keep it as my main AR and register it.