Hello All, I am working on a lightweight build. I have already purchased a light weight .625 gas block. I am pretty sure that I am going to have to tune the gas to run correctly as I have a light weight BCG, and plan on a  light weight buffer.

My question is, does it matter where the gas is tuned? Since I already have the gas block, can I just get an adjustable gas key for the BCG?

Thanks!!!

I have both.

In theory, YES - both work the same way, and are equally effective.

In practice, you need to think about what you want to achieve. Adjustable key is great in "set it and forget it" applications, but if you plan to keep tweaking the gas settings (e.g. different loads etc.), then a click-adjustable block will be more practical.

If you are alternating between "suppressed" and "unsuppressed", then having TWO bolt carrier groups with different gas key settings is a good way to go - just switch BCGs when you install/remove the can. With how cheap BCGs are right now, this is an affordable option.

Thanks, this will just be a range toy so I plan on only shooting plinking ammo through it for the most part.

I went ahead and ordered the adjustable key from Brownells.

Adjustable gas key causes "left over" gas in the gas tube to spew out onto the underside of the handguard. Can make things pretty dirty.   Adjustable gas block avoids that, but unlike a gas key is not easy to swap out. So neither is perfect, it depends on your needs and preferences.

An adjustable gas block will keep the excess gas and particulates out of your BCG and other parts in the lower receiver.
The "key" (pun indented) in your case, being a range plinker, is to have the adjustable gas block as close to the
end of the hand guard as possible, or outside the hand guard, so that it is easy to adjust. It is a real PITA to change an
adjustable gas block's setting when it is buried deep inside the hand guard.

we will see, I ordered a 10" rail and have a 16" predatAR barrel for it.

If it ends up making the gun too dirty and a pain in the ass to clean, I will buy an adjustable gas block.

Thanks for the info everyone!!!

I have a Rubber City adj gas key and it is a pain to adjust and frankly doesn't work well (really at all). I've had much better success with an adjustable gas block. In my case 2 Odinworks. The key is so finicky it's hard to find the sweet spot. Once I did locking down the set screw always changed it.

Id rather limit the volume of gas going in to the upper rather than just the BCG.

I'm a fan of the Superlative Arms adjustable gas blocks.  They have some nice features and work well.

I have the RCA adj key and no problems so far. I started out with the screw blocking approx 1/2 the port/hole and shells were landing at 2:00. Made one full turn adjustment and that did the trick. Now landing at 3-4:00.