I'm in the middle of building my first 300 BLK. I have a 10" barrel and plan on running it both with and without a suppressor. Do I need an adjustable gas block with the pistol length gas system? I already bought a regular low profile gas block and I don't want to spend the money if I don't need to.

Mine is setup the same as yours and shoots supers and subs ... standard non-adjustable gas block

Thank you thats what I hoped you would say. I can spend that money on a good trigger.

no real way to know till you shoot it.

mine was equipped with a standard YHM low-pro, and the NiB BCG would gum up and not work after about 10-12 rounds of supers thru the can.  I'd have to tear the whole thing apart, completely clean and relube, then it would work fine again.  Swapped the gas block for a Syrac Gen 2 and dumped the NiB BCG to a pard who was building a non-suppressed 5.56.

Haven't gotten to shoot it yet, cause my SBR stamp came back and I need to get it sprayed after engraving.  Just haven't had the time to do so yet.  Once the upper/lower/handguard are sprayed, I'll get to the range and get the gas block tuned.

Nah it should be fine without it.  I have a 10" 300 blk with a standard gas block and shoot it both suppressed and not.  It's not necessary on mine, there's not a lot of extra gas with that round.  Now I absolutely run one on my 556 SBR since I am left handed it's very necessary on that gun and makes a huge difference.

The .300 Blackout load was developed specifically for being able to go from standard supersonic to suppressed subsonic without any issue. The gas black does not need to be adjustable. An adjustable gas block just helps your system run smoother and keeps your rifle from being over-gassed. One common sign of an over-gassed rifle is when the brass deflector on the upper receiver is losing its finish or has brass marks "embedded" on it. In some cases, it can also bend the mouth of the case because its being ejected so violently. The adjustable gas block can stop this.