First some clarification on what your configuration is.  Unless I missed it, I didn't see caliber specified so I'm assuming we are talking 556 not BLK.  I am also guessing you have a 10.5" Noveske barrel w/ PSA parts?



I am going to assume we are talking about a 3 position regulator configured for (optimal unsuppressed/suppressed/adverse).  In the case of a DDMK18 or Noveske 10.5, I'd recommend a .073/.049/.082 for commercial ammo and .070/.052/.082 for all milspec ammo diet.  .082 is the port size found in commercial DD 10.3" barrels as well some of the Noveske 10.5's I've looked at.  Note that milspec port size for the 10.3" MK18 is .070" since those guns will never see Tula.  



For optimal performance, you want it to lock the bolt back w/ the suppressor on with the regulator in the suppressed mode....which means it will also lock back in the optimal unsuppressed mode as well as the adverse mode.

For unsuppressed usage, it will NOT lock back the bolt with the suppressor removed if firing with the regulator in the suppressed mode...(unless you want it to by increasing the port size but that just doesn't make any sense).  Most likely won't even kick the brass out.



Now, if your goal is for bolt lock back w/ the suppressor ON or OFF without adjusting anything then don't do get an adjustable gas block and remain severely overgassed when suppressed.  Or I'd recommend going with our 'baby Govnah' to bring the port size down some. As pictured below it is countersunk and pre-drilled to .043".  You can drill it out to whatever port size you want or we can do it for you.

That size will depend on how you plan on feeding it and your buffer/spring configuration.  

However, there is NO FREE LUNCH.  It will still be way over-gassed when adding a suppressor.









 

As seen at the link below on page 4, the milspec port size for the 10.3" MK18 is .070

http://www.dtic.mil/ndia/2003smallarms/john.ppt



In addition the military would be using an H2 buffer and standard power spring.



If controlling the gas, I wouldn't be using a heavy buffer.  I run an H2 and standard power spring (white Sprinco) but I'm also running full auto.

If not running full auto, I'd recommend an H buffer for a 'tactical' setup.



What some people do is tune the gun so the bolt won't lock back without a suppressor and then it will when suppressed.

That is discussed here: http://www.m4carbine.net/showthread.php?33743-Best-Suppressed-SBR-Ever

Still a compromise but it is an option.



See video below to see what a .070 port runs like unsuppressed then suppressed (almost 200RPM faster RoF and more fouling in the action and your face).  Then see what .049 looks like bringing the RoF 100RPM slower than unsuppressed due to the suppressor increasing the dwell time and use of an optimized port.







 

Thanks David!  Yeah, the Syrac's and SLR's are good for what they are and probably the best when it comes to a set screw adjusted block....but I think the Govnah is a slightly different target market.

We have another design that is like 14 settings but never produced it as that is more of the Syrac/SLR market.  

Our target market doesn't want that many settings.  They also want to be able to know what setting the block is in by visually looking at it or by feel in complete darkness.  Forgetting what setting the block is in and having to take a test shot is not acceptable nor is requiring using an allen wrench to change setting.



You can read some feedback regarding the Govnah and MK18's on the MK18 thread here: http://www.ar15.com/forums/t_3_118/641240_Official_Mk_18_and_CQBR_Photo_and_Discussion_Thread.html&page=563

And our thread here: http://www.ar15.com/forums/t_2_543/258195_MK18_and_Govnah_specs.html