TRUBL Posted May 25, 2014 Share Posted May 25, 2014 Built a new upper for 3 gun this year, went with a micro gas block and ultra light barrel to keep everything as light as possible out beyond the Magazine. Anyways.....one thing I figured that I'd try is the RCA ultra light bolt carrier group and something new they came out with....a gas adjustment on the gas key attached to the BCG. Huge Win!!!....I kinda thought having to 'open the rifle' every single time I need to adjust the gas was going to be a PITA.....it was not and besides, i had to do it a total of 4 times.....big deal!! The HUGE WIN......is that there is screw backing up a set screw, so once you find your sweet spot, you can actually lock in in place and not have to worry about it ever coming out of adjustment!! Some are gonna say....well all that extra gas is going into the receiver......not true. The way that the upper is designed and the 'gas joint' in that area.....any extra gas goes forward into those 4 little holes that surround your gas tube and out into the hand guard. BTW.....as the AR15 is over gas to begin with, it's already doing that so I was not worried at all about any 'extra' gas getting into the receiver. Infact.....as you are turning the gas down (just like on an adjustable gas block).....less gas is getting into your receiver. I ended up turning the screw out about 1.5 turns from being shut off......YMMV as I was using my LW recoil system. Anyways.....it was easy to adjust.....easy to lock and allowed me to use that really sexy VLTOR gas block I've had sitting in the shop for the last year. I do believe that RCA sells just the adjustable gas key....so you can use it with your BCG. Tim Link to comment Share on other sites More sharing options...
midengine3sgte Posted May 26, 2014 Share Posted May 26, 2014 How do you like it? Link to comment Share on other sites More sharing options...
TRUBL Posted May 26, 2014 Author Share Posted May 26, 2014 I like it a lot......and for people wanting to have adjustable gas, will not have to go thru the hassle of removing a comp, current gas block, gas tube, etc...to switch over. Yes, you will have to re-stake the screws.....but that is rather easy with a punch and hammer.......no real tear down. I see it as a win-win!! Link to comment Share on other sites More sharing options...
midengine3sgte Posted May 26, 2014 Share Posted May 26, 2014 cool thanks. I think I'll give it a try on one of my builds. to many projects at on time. Link to comment Share on other sites More sharing options...
frsteve Posted May 26, 2014 Share Posted May 26, 2014 @trubl - if you have adjustable gas block already, what benefits can be added on top using an adjustable gas key? Thx Link to comment Share on other sites More sharing options...
TRUBL Posted May 26, 2014 Author Share Posted May 26, 2014 (edited) @trubl - if you have adjustable gas block already, what benefits can be added on top using an adjustable gas key? Thx Not sure why you'd want the adjustable key...if you have an adjustable gas block.....I'm thinking that it is more of a either/or thing. On the plus side......it's not going to get quite as hot as the gas block. Tim Edited May 26, 2014 by TRUBL Link to comment Share on other sites More sharing options...
StealthyBlagga Posted May 27, 2014 Share Posted May 27, 2014 I just ordered RCA's complete lightweight carrier with adjustable gas key. Weight looks to be comparable to a JP carrier. I'm going to set it up in an 18" rifle with regular gas block, and compare performance with an identical rifle built with a Syrac block and JP carrier. Link to comment Share on other sites More sharing options...
midengine3sgte Posted May 27, 2014 Share Posted May 27, 2014 I just ordered RCA's complete lightweight carrier with adjustable gas key. Weight looks to be comparable to a JP carrier. I'm going to set it up in an 18" rifle with regular gas block, and compare performance with an identical rifle built with a Syrac block and JP carrier. I'd like to see the result of that test. please keep us informed Link to comment Share on other sites More sharing options...
george995 Posted May 27, 2014 Share Posted May 27, 2014 (edited) gonna have to try this out, was looking into an adjustable gb for my 308ar. I like this because of its price at $45 and if you do not have an adjustable on your rifle you aren't stuck with your original non adj. GB. Parts are good to have on the side for future builds, but say you paid $60 for a vltor originally and now shell out $100 for a syrac or etc., thats $160 (without shipping) you got into Gas blocks. This is assuming from a build standpoint. Edited May 27, 2014 by george995 Link to comment Share on other sites More sharing options...
rugerdawg Posted May 29, 2014 Share Posted May 29, 2014 I am running an 18" JP lw barrel with rifle gas, JP full mass carrier with a JP captured spring set-up and a non-adjustable gas block. Would I benefit much from an adjustable gas system? If so, changing out a gas key clearly would be easier than the gas block route, all other things being equal. Link to comment Share on other sites More sharing options...
StealthyBlagga Posted May 29, 2014 Share Posted May 29, 2014 I am running an 18" JP lw barrel with rifle gas, JP full mass carrier with a JP captured spring set-up and a non-adjustable gas block. Would I benefit much from an adjustable gas system? If so, changing out a gas key clearly would be easier than the gas block route, all other things being equal. You will gain a lot more by going to a lightweight carrier coupled with that adjustable gas device (whether block or key). Link to comment Share on other sites More sharing options...
PepeBangBang Posted July 3, 2014 Share Posted July 3, 2014 Stealthy Did you run that test? Results? Link to comment Share on other sites More sharing options...
StealthyBlagga Posted September 10, 2014 Share Posted September 10, 2014 (edited) Sorry for the slow update. I hit a few roadblocks with this carrier that prevented me from doing the side-by-side comparison I had wanted to do. Lets start from the beginning: The RCA lightweight carrier with adjustable key is actually a very well made piece. The melonite finish on the parts is really nice and, along with the lack of machining marks, solid staking etc., inspires confidence. Here is a photo: Up close you can see where the gas regulating set screws are installed: The set screws are removed in the photo below so you can see the relative sizes: Both appear to be standard 8-32 set screws The left-most is 3/16" long, is inserted first, and protrudes into the gas stream to regulate flow. The right-most is 1/8" long, gets installed second, and serves as a lock-screw to hold the gas adjustment screw in place. This is where I encountered my first problem; the locking screw is just a regular set screw with knurled tip - as a result, screwing it in actually caused the gas adjustment screw to turn as well, messing up the gas adjustment. I fixed this by grinding the tip off the locking screw, and by blue Loctiting the gas adjustment screw in place before installing the locking screw. Sorry for the blurry photo below (original on right, modified on left): With the ability to lock-in my adjustments, I headed off to the range to adjust the system. This is where I hit my second bump in the road. Using the gas adjustment screw only, I managed to get a good adjustment range - perhaps too good. Fully screwed in, the bolt carrier did not move, but it took a full 2.75 turns out before the bolt would reliably lock open on an empty magazine (RCA says it should be only about 1.5 turns). Ammo was close to M193-spec, so not weak, and it behaved the same with different ammo and magazines. The problem with having to wind the gas adjustment screw out so far was that the locking screw now had insufficient threads to secure it reliably, and it would protrude from the back of the key. This did not seem right to me, especially with a light-weight carrier and buffer (CAR buffer with weights removed), so I spoke to Chris Cerino, who is involved with RCA, and he confirmed the same experience. His theory was that the rifle gas system just does not produce enough gas. I am not sure I totally buy this, as I tried the same carrier in some higher-pressure systems - a 16" midlength, a 14.5" carbine and even a 12.5" carbine, and the gas adjustment was in a similar range for all the uppers. Maybe my carrier or key has some other problem, but in the end my solution was simple - I traded out the 3/16" gas adjustment screw for a shorter 1/8" screw (from Ace hardware). This shorter screw let me get optimal gas adjustment and still fit the locking screw in behind it. Wanting to get my 18" rifle up and running, I had already installed a Sentry adjustable gas block (another new toy, which I love). Thus, the RCA carrier went into another new build - a 14.5" lightweight. This upper has a non-adjustable gas block as I plan to permanently attach the muzzle brake and I want a no-moving-parts system attached to the barrel. After adjusting the gas system, this upper has shot with agreeable softness and stability. So far, with about 1000 rounds through it, this set screw arrangement appears to be holding up well, with stable adjustment and ZERO malfunctions. This is where things stand right now. I will shortly be replacing the jammed-up Syrac block on my Open/Tac Scope rifle with a Sentry block - when I do so, I will be able to revisit the comparison of the adjustable block/JP LW carrier vs. adjustable key/RCA LW carrier. I will post my further impressions then... promise Edited September 10, 2014 by StealthyBlagga Link to comment Share on other sites More sharing options...
practical_man Posted September 11, 2014 Share Posted September 11, 2014 SB - Thanks for the review. Very helpful as I am beginning the process of experimenting with adjustable gas systems. My rifle has a non-adjustable block and mil-spec carrier. This looks like a good solution to two problems. -john Link to comment Share on other sites More sharing options...
lumberjack149 Posted September 11, 2014 Share Posted September 11, 2014 My brother in law has had a few problems with one i installed on a 16" midlength gun, carbine buffer. I originally adjusted per their instructions and ended 1.5 turns from closed (cycled and locked back at 1.25 turns), i then put in their set screw and started having malfunctions right away and discovered that the set screw walked the adjustment screw forward (as mentioned above). I took it back apart, reset everything again, added another 1/4 turn for safety, used blue lock tite and carefully set the set screw (stopped once i felt it bump the adjustment screw). Everything worked fine for the next 100rds until he took it to a USCA 2 gun match and started having problems and by the end of the day he had a single shot rifle. When we got back home and took it back apart we discovered the adjustment screw had walked itself almost shut (it was 1 turn from closed). This time we made sure we cleaned the threads (so the lock tite will hold better) and used red lock tite (shouldnt come apart) Time will tell if this works. It has been a headache and the whole "set screw" is less than perfect. Link to comment Share on other sites More sharing options...
MickB Posted September 11, 2014 Share Posted September 11, 2014 Somebody needs to adapt the SLR leaf spring system to the gas key to be able to hold the gas adjustment screw in place.... Mick Link to comment Share on other sites More sharing options...
Stlhead Posted September 11, 2014 Share Posted September 11, 2014 OK, I might be on crack, but why couldn't the gas adjusting set screw have the allen key opening on the gas side, so you could use two wrenches at the same time and hold your setting while you torqued it down? Link to comment Share on other sites More sharing options...
StealthyBlagga Posted September 11, 2014 Share Posted September 11, 2014 OK, I might be on crack, but why couldn't the gas adjusting set screw have the allen key opening on the gas side, so you could use two wrenches at the same time and hold your setting while you torqued it down? On the RCA design, the set screws run downwards at an angle - I doubt you could reach them from the front of the gas key. I recall that Sun Devil offers something similar, on which the set screw DOES run parallel with the key, so your approach might work in that case. Link to comment Share on other sites More sharing options...
lucas Posted September 11, 2014 Share Posted September 11, 2014 OK, I might be on crack, but why couldn't the gas adjusting set screw have the allen key opening on the gas side, so you could use two wrenches at the same time and hold your setting while you torqued it down? On the RCA design, the set screws run downwards at an angle - I doubt you could reach them from the front of the gas key. I recall that Sun Devil offers something similar, on which the set screw DOES run parallel with the key, so your approach might work in that case. Wow, looked it up, got to check that out. I think I want to compare to my RCA. Link to comment Share on other sites More sharing options...
Dan Sierpina Posted September 12, 2014 Share Posted September 12, 2014 OK, I might be on crack, but why couldn't the gas adjusting set screw have the allen key opening on the gas side, so you could use two wrenches at the same time and hold your setting while you torqued it down? The angle of the set screws is 45 degrees. A ball driver will work up to 15 degrees, so that won't work. I bought a RCA key, and you do have to over adjust it to compensate for the movement when locking it down with the short set screw. That took maybe 15 minutes at the range to get the proper adjustment, then Loctite the short set screw, and back to shooting. I then drilled and tapped the key that I removed to install the RCA key. The parts are not hardened. The adjustable key allows you to go with adjustable gas without removal of your comp and gas block. It may prove less ammo sensitive than a gas block, since it is at the far end of the gas system. Or, maybe not. Link to comment Share on other sites More sharing options...
logiztix Posted October 9, 2014 Share Posted October 9, 2014 Based on the one I received last week, it appears that there has been a revision or two to the RCA Adjustable Gas Key. Mine shipped with two shorter stainless steel set screws, rather than one short and one long. Each set screw also had thread-locking compound already applied. I haven't shot more than 50 rounds since installing it in a DPMS 20" Bull Barreled upper, but it seems to be holding the setting just fine so far. Link to comment Share on other sites More sharing options...
gliney00 Posted October 11, 2014 Share Posted October 11, 2014 I am trying to wrap my head around the adjustable gas key. If you choke the gas system at the barrel via a adjustable gas block, most of the gas finds the path of least resistance and follows the projectile down and out the barrel. a decreased amount of gas travels down the gas tube and into the BCG. unlocking the bolt and acting on the carrier But if you choke the system at the gas key, the full gas pressure enters the receiver and is choked down at the gas key, once the bolt is unlocked, is the full gas pressure acting on the carrier? Link to comment Share on other sites More sharing options...
jtaylor996 Posted October 11, 2014 Share Posted October 11, 2014 (edited) The difference is only the volume of the gas tube itself at the higher pressure. That's not much at all. A restriction anywhere before the rings on the bolt is going to put more gas down the barrel. Edited October 11, 2014 by jtaylor996 Link to comment Share on other sites More sharing options...
EaZeNuTZ33 Posted October 15, 2014 Share Posted October 15, 2014 Look slike a solid option IMO. I won a rifle this past weekend that I'm thinking will be great for my son to use as his first 3-gun rifle....will be pretty nice to just to swap in the BCG with adjustable key, add comp, Taccom ULW buffer system and tune! Link to comment Share on other sites More sharing options...
TRUBL Posted October 15, 2014 Author Share Posted October 15, 2014 I am trying to wrap my head around the adjustable gas key. If you choke the gas system at the barrel via a adjustable gas block, most of the gas finds the path of least resistance and follows the projectile down and out the barrel. a decreased amount of gas travels down the gas tube and into the BCG. unlocking the bolt and acting on the carrier But if you choke the system at the gas key, the full gas pressure enters the receiver and is choked down at the gas key, once the bolt is unlocked, is the full gas pressure acting on the carrier? The gas that is bled off into the gas tube only does one thing.....unlock the bolt. Once the bolt is unlocked.....you are then relying on the pressure in the barrel to push the bolt back. Essentially.....when you retard the amount of gas going into the bolt carrier (whether at the gas block or gas key).....you are determining the amount of pressure that is available to 'blow' the bolt back. By retarding the bleed off gas.....you are allowing the bullet to travel farther down the barrel before the bolt unlocks. The farther down the barrel the bullet goes.....means that there is less pressure available to blow the bolt back. Now.....as to where you retard the bleed off gas? Gas block or Gas Key...this happens in a VERY short period of time and while you could go thru the numbers as to why one is 'technically' better than the other......there really is not a vast amount of difference in the two systems. FYI......with a gas key adjustment and more unused gas entering the receivers......there is nothing to worry about there. take a look at your uppers, ever notice that 'clover leaf' where the gas tube enters? That was not done so that there was less touching the gas tube......it's a vent for any unused gas from the gas key. Infact, if you look at your rifles, you'll probably notice a little carbon there already......that just means it's working. In the scheme of things....using an adjust gas key is just another way to skin a cat, will not introduce any more gas in to your receiver and well, works great from what I've seen so far. It's been easy to adjust.....you might think popping the pin out is a pain.....but I've not noticed it to be really any more time consuming than doing a gas block. Tim PS.......I know I used the word 'retard' and but I only used it in a technical stand point, not a derogatory standpoint. Link to comment Share on other sites More sharing options...
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