When it gets out of NFA jail will I be able to slap my suppressor on it and it function flawlessly? What am I facing? I have read they are already over gassed; things to look for and recommendations.

They are a bit over gassed. I put a H3 buffer in mine and it has run flawlessly both suppressed and unsuppressed.

H3 is solid advice

H3+Sprinco BLUE.

Do their MK18 barrels have the same size gas port as their standalone 10.3" barrels? If so, it might not be as easy as just slapping an H3 buffer in it and heading to the range. I have a DD 10.3" barrel and have had a hard time getting it to cycle reliably since getting a suppressor. I've stepped all the way up to a Heavybuffers XH buffer and Wolff XP spring to no avail. So with the weight maxed out I decided to give LMT's enhanced carrier a try. I haven't had a chance to get it out the range yet with the suppressor unfortunately so I'm not sure if this has helped yet, but it does cycle fine unsuppressed still.



You maybe be better off saving yourself the money and trouble and getting an adjustable gas block. I wanted to avoid it, just to see if I could make it work without one. At this point I could have bought 3 or 4 adjustable gas blocks, and I still don't have a rifle that cycles both suppressed and unsuppressed. If you don't want to get an adjustable gasblock, there is always the option of purchasing the Baby Govnah, having it drilled out to the same port size as an actual MK18 gas port, and experimenting from there.



Note that this is just my personal anecdote on DDs 10.3" barrel. Your mileage may vary.

 
That's what I use in my MK18 and it runs anything I feed it.

They are simple and reliable from my expedite with DD 10.3" barrel. Pick up a H1, H2 and maybe H3 buffers to compensate if there is to much gas. Another way is to get and adjustable has block.

An A5 system would also be worth considering.

Have you fed it tula steel?
I have an 11.5" and think I can get away with an H2.

I put an h2 in mine, runs like a champ, I dunno people complain so much about the gases, unless your mag dumping it's not bad at all, but hey that's just me.

Govnah & H2 buffer in mine; shoots like a dream; note i only shoot 55gr brass out of mine. I do however have 1 of 3 settings set to the factory .70 .082 to run it all (.070 - .049 - .082)

eta: info

It's a pretty common/proven configuration.

Wolf, yes; Tula no:  have not tried it.

Not that the Wolf is marginal enough to make me think Tula wouldn't run, but (per the Lucky Gunner testing) it has some known "problems" with it's pressure curve that make me no want to run it in my other guns...so no Tula in the house.

 
The only steel cased ammo I've shot out of it was Hornady, which worked as well as the others.

so an H2 would be fine?

I have a Spike ST-2 buffer and swapped the DD BCG for a Colt BCG and ut runs 100% both suppressed and unsuppressed. I get much more gas in the face compared to my Colt Mod0 MK18

 
Why trade out the DD BCG for a Colt BCG?

Vltor A5 system and an adjustable gas block.  Recoils like a rimfire.

I use a VLTOR A5 in mine and the muzzle barely rises