I am trying to build a 13.9 pin and weld build that is suppressed. I wanna know if these parts will work together? I dont know if it will be 16 inches overall, and I dont know if the suppressor will make contact with the hand guard? Thanks.

Option 1:
Midwest Combat Rail(13.375")
Ballistic Advantage Barrel(13.9")
Dead Air Muzzle Brake(2.6")
Dead Air Sandman K Suppressor(5.4")

Option 2:
Midwest Combat Rail(13.375")
Ballistic Advantage Barrel(13.9")
Surefire SOCOM Muzzle Brake(2.6")
Surefire Mini 2 Suppressor(5")

Either will be real close on length, depending on how far the tenon is threaded on the barrel.  13.9+2.6-.625=15.875, so would need a little help getting there.

I can speak to the Mini (get this one, it is awesome) and it will be close, but as long is it is those dims exactly, you will be fine.

Question 1:
Barrel Length(13.9")+Muzzle Length(2.6")-Thread Length(.625")=15.875"
Shims or Crush Washer? Demensions of Shims and Crush Washers?

Question 2:
Barrel Length(13.9")-Thread Length(.625")-Handguard Length(13.375")=  -0.1"
If my math is correct, the handgaurd will cover 0.1" of the threads. Do the suppressors sit flush with the muzzle devices I mentioned in my previous post? Do they extend past the muzzle device toward the barrel, or do they retract toward the port of the muzzle? I hope this make sense. If I have to shim or extend the muzzle device, then this question doesn't really matter too much. Thanks

Q 1:  Shims > crush washer for suppressor mount.  How many will depend on how they measured the barrel and how long the tenon.

Q 2:  There is no common spec for suppressors so you won't know until you get it together, unless someone here already has your handguard/barrel/suppressor/flash hider combo.  There is a lot at play here.

Crush washers and cans do not play nice together.  

Check out the SOLGW NOX mount (for Dead Air can) or Surefire Warcomp mount (for Surefire can); either one will get you to 16" pinned and welded without shims or spacers.

The SOLGW mount will also be long enough with a 13.7" barrel, which will give you a few more barrel options than trying to source a 13.9".

Can't personally say if the Warcomp + 13.7" will make it to 16", but it should be very close.

Expo-Forward Controls Keymo muzzle brake is 2.7” and they claim it reaches 16” OAL with a 13.9 Bbl.

I used a 13.9 Ballistic Advantage barrel, Midwest Industries Combat Rail (13.365), and a Surefire 3 Prong Warcomp. The Warcomp has a slightly longer thread shoulder than the Surefire standard 3 prong or muzzle brake. I have been using mine on a Form 1 lower, but will get it pinned here in the near future. I have measured the overall length and it is 16 and 1/16th inches. I used the proper amount of shims to time the Warcomp in the neutral position, which probably gave me the extra 0.00whatever to get it to a legal length once pinned and welded. If you're in the market or have already purchased a Surefire suppressor, then that is your best option. If you haven't committed to a suppressor yet, then I would recommend the SOLGW NOX muzzle device, since it is plenty long and will give you approximately a 16.25 inch overall length. I did get a 13.7 inch barrel to 16.1 inches, but I sent the barrel and Warcomp off to Retro Arms Works and had John Thomas make me a custom spacer, install the Warcomp, then pin and weld it. John does excellent work and I will send my 13.9 off to him for the pin/weld job.

13.9 Criterion Core and pinned Surefire Warcomp got my build over 16"

I for one feel bad for you that you have to go thru this ridiculous barrel length thing so you don't have to be labeled a felon. It's just utter horseshit.