I am building an 11.5" carbine in 5.56. Gun will usually be run suppressed. I can't give you a percentage, because I probably wont run classes suppressed all the time, but shooting at my ranch will always be suppressed. Do I really need an adjustable gas block? Should I just deal with the little extra gas in the face? I don't have an adjustable gas block on my 16" middy, but I wasn't sure if it would be necessary on a SBR for some reason. I've read some comments about "a properly built AR will run fine with any ammo and suppressed/unsuppressed without [fill in the blank part name]" while doing research, so thought I would check in here. Leaning towards a govnah if I do get an adjustable one. Thanks for any insight.

What barrel?

I've never had to use an adjustable gas block and until I have problems, I never will. I have a DD MK18 upper (10.3") with a Spike's T2 buffer and run suppressed 75% of the time. PRI Gas Buster charging handle too. Never noticed gas to the face and its run flawlessly on large variety of 5.56 ammo and Hornady .223.

The technical answer to whether or not you "need" an adjustable gas block is no. You can get the rifle tuned in other ways. The simpler answer is that the gas block is the easiest, and often cheaper way, to tune the system.

Those comments you mention should be saying "a mil-spec AR" doesn't need those parts. Stoner's original design works because it was tested and proven. However, when we start fooling around with different specs is where we alter the timings related to the original design. Just look back to when the original system was fielded by the military, and the problems that they had because they used a different powder in the ammunition than what Stoner developed the system with. When we start throwing in commercial ammunition that isn't mil-spec, different barrel and gas lengths, various bolt carrier mass, buffer mass, etc. things can get out of balance from that original design. This is where the Adjustable gas block helps you tune the rifle to bring all of that into balance. It isn't just because of the DI system, or just gas operated systems that suffer from this, either. HK's roller lock system had growing pains every time ammunition was changed, as well. Now you can get rollers and locking pieces of various dimensions to tune that system.

If you already have a bin full of various weight buffers and bolt carriers, then the adjustable gas block will be an added expense. If you don't already have a bin of parts like that, then the gas block will save you from having to buy one.

What bbies1973 is saying makes a lot of sense to me.  There are so much conflicting info on the net and also on this board that its really hard to have a clear cut answer because there are so many variables involved.  I decided to find out myself by doing a lot of experimentation.  One thing is clear (to me), that if you will be employing a lightened reciprocating mass system (BCG, buffer, etc) that some way to adjust the amount of gas pressure going into the BCG in a DI system is an effective and relatively simple method to control the recoil characteristics and reliable cycling of your rifle.  But you do have to pay attention to the ammo you are shooting and the cleanliness and lubrication of your rifle and it's components.  All other variables staying pretty much constant, these are the main factors that can produce reliability issues.  For example, just lightly greasing the buffer spring on my rifle made a difference if the BCG would lock back or wouldn't on an empty magazine with the same gas setting and ammo.  This surprised me as to how sensitive the system really is.  

I don't think any of us can give you a clear recommendation, and its really up to you if you can afford the extra cost, and the effort to tune your system (and keep it in tune).

Haven't bought the barrel yet, but was going to get a ballistic advantage. Does barrel choice make a difference?

So you just use a heavy buffer and not worry about extra gas in the system?

I don't have any of those parts. I was under the impression the most efficient way to tune the rifle for shooting unsuppressed/suppressed was an adjustable gas block instead of trading out bcg and buffers until it ran well. A simple flick on the govnah when I take the can off should make it run just as well as it did in suppressed mode, theoretically, right?

How much effort does it take to actually tune these plates for an adjustable GB? Does it require a drill press and extreme precision or can I bring a cordless drill and a C clamp to the range and bore out the holes appropriately there?

The has port size on whatever barrel you get is going to determine how it runs.

I believe the standard 10.3"  gas port is approximately .072"

I have no experience with the Govnah, so I can't say for sure what it takes to get one tuned. I use blocks with an adjustment screw.

I think the biggest concern with tuning a plate for the Govnah would be making sure you had a precise set of drill bits - oh, and a couple truck loads of patience. You would need a good selection of gauge sized bits (usually called "numbered" bits), rather than fractional sizes. The difference from one numbered bit to to the next gets down to ten thousandths of an inch rather than your usual 1/16 and 3/32, or even 5/64 kind of things, here. Those bits are in the size range that you are looking for, but the increments between them is too much. Likewise, when it comes to increments this small, I just don't know that I would trust a $10 set of bits to not have loose tolerances. I'm thinking you would need something in the range of 40 and up (larger number = smaller bit). I would probably go at least to a 60. Those bits should cost anywhere from $1-$2 each with the price going up as the size goes down.

Once you get that Govnah tuned to your rifle, it will be as easy as you had hoped. It's getting there that could be the struggle. You might get lucky with their standard predrilled plate, or you might not.