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Adjustable gas blocks are great for competition shooters. With the turn of a couple screws you can turn an ultra-reliable yet hard recoiling rifle into a veritable pussycat, allowing you to get back on target faster after each shot. While it’s a great feature, retro-fitting existing guns to have an adjustable gas block is a bit of a pain. For those who have run headlong into this problem, Rubber City Armory has a solution . . .

Instead of cutting off the gas at the gas port, RCA decided to ut the adjustment at the other end of the gas system. It makes adding this feature to your gun a breeze, and makes adjustign the gas system just as easy. Instead of needing to take the handguards off to get at those adjustment screws, you can just remove your bolt carrier and make your changes there.

RCA will be making these available in every way they can, from adding them to their existing “low mass” bolt carrier to making them available as a standalone product. As for a price point, they’re looking at somewhere under $40 — less than the price of the gas block version.

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  1. This also allows you to use the gas block you want rather than the adjustable one that may not have other features you need. Good all around and at a reasonable price as well. Look like a winner.

    • That’s pretty much what I was going to say. +1 However, an adjustable gas block is often more easily accessible and probably a faster adjustment.

      • How often are you going to need to adjust it? If you switch between suppressed and unsuppressed, sure, but for most it’s going to be set for their favorite load and never touched again.

  2. I did not see from the pictures any thing preventing your new adjustments from becoming unadjusted. What I mean is, on all of my adjustable gas blocks their is a push pin I have to depress so I can make the adjustments I need. Once set the adjustment is secure. I didn’t see any thing on this new device to prevent the adjustments from walking them selves out of ajustment. Also with the orientation of this ajustment screw, if it ever fails I can see that little screw flying back into your recover group with force causing who knows what king of damage.

    • The RCA key block comes with three 1/8″ adjustment set screws. Basically what you do is dial in the adjustment and then throw another set screw on top of the adjustment screw to lock it in place. I have an RCA key staked on my BCG for the last 5k rounds and have had nothing but good luck and a properly running rifle(no 1-2 pm ejection, case head swipes, mid case dents..etc.). The upper and front of the gas port receiver entrance does get alittle dirtier but not by much. I only have it opened 1 full turn because the gas port on my YHM47TF is oversized, there is NO extra wear on my bolt orlocking lugs or extension.I know I can run a gas block but wanted to try this out at a fraction of the price and it works great. There is high temperature locktite supplied on the adjustment screw, locking screw and extra screw. Try it.

  3. I’m in need of some learning. Won’t the full amount of gas still hit the gas key moving the BCG? How will that improve recoil? Adjusting the gas through the key will smooth out the bolt. Adjusting the gas through the block will smooth out the whole operation.

    What am I missing?

    • May be more of a release than a clamp down on the gas. A regular adjustable gas block limits the gas going in to the tube, this would probably allow some of the gas to just bypass the system kinda like blowing a spitwad through a straw with a hole in the side.

    • I want to know this too. Does it constrict the amount of gas going into the BCG? Where does the excess gas bleed to? Does it go out the back of the gas key where that set-screw is? Does it just prevent it from leaving the gas tube?

      These things must be known…

      • It gets vented back into the upper or more specifically, back out the X where the gas tube comes through and just makes the barrel collect slightly more carbon. Gas pressure is reduced and the above poster was correct, it acts more like a relief. 52k psi of carbine gas and maybe only 5k gets into the key to do the job of unlocking the bolt face. I have been watching for wear on my Bushmaster XM15 bolt or YHM extension and both look great. You are just throttling the gas but vent some to slow the action down and let the dwell time go up. I have no complaints that my upper is more noticeably dirtier at 300-400 rounds but it is not much more than my others, if anything the barrel near the receiever just needs a wipe. Try it.

  4. The way the gas key operates is it guides gas in to the BCG’s gas expansion area(I forget the name) behind the bolt thus unlocking the bolt and then allowing the BCG to move backwards. This brings another question to the fray. Won’t this put in needed pressure on the bolt and the barrel athte place where t locks in to place?
    Corrected due to phone auto corrections. Err.

  5. Looks like a good deal to me. Probably be really nice when you have an extra long free float handguard on your rifle as well as having the ability to use the same bolt in multiple uppers with different barrel lengths and configurations. Just bottom the adjuster and then back it off a certain number of turns for each one you have used before to get the settings ready.

    Just wondering the ETA for public use and where it can be acquired from.

  6. “…hard recoiling rifle…”

    We’re talking about an AR here, right? AR’s in 5.56 or .223 Remington, right?

    If you think a .223 is “hard recoiling,” then, well… sigh.

    I think I’d stick with the adjustment on the gas block. I can shoot, adjust, re-shoot, re-adjust with the handguards off. I can’t do that so easily by pulling out the BCG every other shot.

    And, BTW, I don’t like pondering what will happen if that adjustment screw on the back end of the key backs all the way out.

  7. If you have a long pipe with a fluid flowing through it, it does not matter where on the pipe you place a valve to control the flow. The valve can be placed at the beginning, middle (gas block), or end (gas key). The result is the same.

  8. Welp I will say Jeff gave me great service recently, I pulled out a carrier with some considerable shooting on it, hadn’t been moved or adjusted in over a year. I used the two small screwed , one to adjust and one to lock it in. The inner screw wouldn’t budge and eventually fubared up. Jeff was kind enough to accept it in and replaced the entire key with a mid 3 design, I think I’ll be using the single large screw design instead of the smaller ones. Gun shy now about the smaller ones.


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