View Full Version : New Drop in adjustable gas system
hypercruiser
04-05-14, 11:24
Adjustable gas system by Sun Devil MFG. Sits on the carrier for easy access, no handguard to get in the way. Adjustment is at the lowest point of gas pressure for precise adjustment. See for yourself: www.dropingassystem.com
24933
Redbeardsong
04-05-14, 11:48
Interesting. I'd be concerned about stress cracks forming around the sharp edges on the key, though. I wonder how well the set screw stays in place.
Ned Christiansen
04-05-14, 12:19
Post edited so as not to cause any complications for SunDevil.
Basically I think it's a good idea for some applications and certainly is an easy way to give regulation a try. I'd like to see a split pin in the key behind the set screw to block it from ever coming out although being as how it is exposed to the gas stream and all the particulates it carries, it's probably not ever going to be loose. And thread the hole so the screw can't go in too far. And my other suggestion would be to leave the key at the spec hardness so as not to preclude a proper staking job; the last two of which they probably already considered.
This has really peaked my interest, I'm debating ordering one.
I just put some rounds through a LMT MRP CQB 10.5" URG running a LMT E-BCG on a A5 lower with a green Sprinco spring and A5H3 and the damn thing felt harsh compared to my other URG, a LMT 10.5" FSB setup on the same lower. It would be an interesting experiment to say the least, especially if the setup proves to be reliable. Based on Ned's comments, I believe the carbon will keep things in place once it is dialed in.
Well I freaking just ordered three kits, I'll post up some detailed info / pics once I get them in to include a T&E on my recent 10.5" LMT MRP CQB URG setup that will eventually find a home on its own papered lower.
hypercruiser
04-05-14, 16:09
The set screw has a nylon button, blue Loctite just finishes it off. Same as the tension screw in the lower, only smaller. It has been tested in competition rifles since beginning of January without a hiccup.
The set screw has a nylon button, blue Loctite just finishes it off. Same as the tension screw in the lower, only smaller. It has been tested in competition rifles since beginning of January without a hiccup.
What? Why would the setscrew have a nylon button? Is that a nylon tip or a nylon cap to seal the threads?
hypercruiser
04-05-14, 16:19
What? Why would the setscrew have a nylon button? Is that a nylon tip or a nylon cap to seal the threads?
It is in the threads to prevent movement after setting.
No issues with heat soak? Can you post pics?
Hopefully this works better than some of their out of spec uppers and lowers.
BufordTJustice
04-05-14, 17:01
I would use red high temp loctite on the adjustment screw once you find the proper settings. It dissolves on contact with super glue solvent, but is quite resistant to torque and temp.
Sent from my SPH-D710 using Tapatalk
hypercruiser
04-05-14, 17:02
No issues with heat soak? Can you post pics?
24939
Thanks for that pic, what is the size & thread pitch?
Hopefully this works better than some of their out of spec uppers and lowers.
You must not be using DPMS parts.
I wouldn't trust SHIT that came from Sun Devil MFG.
Well I will end up finding out as soon as my order is received, I'll update this thread with my findings.
jerrysimons
04-09-14, 23:18
I hadn't seen this. How are yours working out for you? Not so sure I understand how this solution regulates the same as an adjustable gas block, do not the gasses start to push the BCG reward as soon as they enter the key?
I will have mine before the week runs out and plan to update the thread here with my findings....
No the gas will not push the BCG rearward first because of the way the system is designed, it has to unlock first, which is handled by the gas entering the BCG and pushing the bolt forward while the carrier is pushed backwards with equal pressure until it unlocks, then bleeds off excess gas and continues its travel rearward. Regulating the amount of gas that makes its way into the chamber the bolt rides in via the key or the gas block both achieve the same thing. The only exception I can think of is not reducing the fouling, as it will stay the relatively the same as it was before vs. regulating it via the gas block can reduce this in a very minimal way.
Anyways lets post about the adjustable gas key in the adjustable gas key thread and keep this one on topic, unless V7 decides to make their own gas adjustable carrier key.
http://4.bp.blogspot.com/-2F9CKeP9gy8/UiWmMSeO6vI/AAAAAAAACHs/5LL1OKKdupo/s1600/023.gif
Ah, I think I see what you are saying now. Though, theoretically, if the set screw completely shut off the gas at that point in the gas key would there still be a force attempting to move the carrier rearward from the gas pressure on the key itself? What happens to the excess gas, does it vent back out through the gas tub and out of the barrel?
If the excess gas kept from entering the carrier vents out around the key as the BCG moves rearward and exposes the gas tube, it seems that this method of regulation might not be as effective as regulation at the gas block at cutting down on excessive gas in the upper when suppressed.
Will one of you experts please help me understand?
Looking forward to your results E-Man, think I might order one for a JP low mass carrier set up.
Lots of other factors dealing with pressure, volume, and flow all have to be taken into consideration when looking at the design of the DI gas system.
If one were to close off the gas key all together, the system should not cycle properly because of it's design, but I would like to test this out myself...
Anyways be back in a few with some pics...
Based on my visual observations, the keys do not have a chrome lined interior nor have they been melonite treated. The finish appears to be some sort of an oxide finish or possibly a smooth park, an inquiry to Sun Devil did not yield any details. The do seem to have some sort of hardening based on my best judgement, and have some well machined portions and some with some deviations. If you take a look at the picture with all three of the gas keys on their side you can see differences between all three keys. While this may only not affect the function of the part and may only be a cosmetic issue, I take the conformity between parts to be somewhat of an indicator of the manufacturers ability to hold consistent production between parts. I will, however, reserve my judgment until I can test the functionality of the ADIGS. In the mean time feel free to peruse these pics. Also, if you have a suppressed SBR, and have the time and ammo to run around 750-1000 rounds through your carbine and are interested in a free ADIGS kit for evaluation purposes, please PM me. I purchased three keys from Sun Devil with the intent of testing all three on three different carbines and the two buddies that initially got excited admitted to me that they don't have time right now to hold up their end of the bargain... I'm going to mail you one of these I would like to see your feedback posted here, good, bad, or ugly - for the good of the community. I feel like Sun Devil may have a really good thing on their hands right now but I'm not a fan of the nylon insert in the screw, but so far I haven't proved their testing wrong to otherwise gripe about it now. I plan on installing one kit over the weekend and getting a good 250 round session in before the weekend runs out. Also, before anyone assumes anything, I have ZERO affiliation with Sun Devil or this product beyond believing in it's potential from a conceptual standpoint and blazing the trail as an early adopter with a streak of skepticism.
http://i.cubeupload.com/4Xp51g.jpg
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jerrysimons
04-11-14, 20:30
I too ordered this part. It will go on a JP low mass carrier. Very curious to see how it pans out.
A phone inquiry asking the questions posed in previous post provided a little more info.
-The keys are stakeable, i.e. it is not hardened so as to preclude staking. Though Sun Devil's position on staking is that it is unnecessary when using red loctite and not recommended since "you may eventually have to reseal the key to the carrier with the red loctite for a complete gas seal".
-One of the differences between the ADIGS and an adjustable gas block is the pressure in the gas system at point of regulation. Apparently the pressure is lower in the gas key than it is at the gas block, which is claimed to allow the ADIGS a more sensitive range of adjustment ove an adj. gas block. The fellow on the phone said "you can adjust your ejection pattern with it".
-On the same line about the difference in the effectiveness of regulation methods he said that the gas does exert some reward force on the gas key itself but that it is negligible (does this increase the more choked off the key becomes? Idk). This seems at odds with the claim that it is more sensitive but I lack the expertise to know.
Looking forward to real world testing.
jerrysimons
04-16-14, 22:28
http://i8.photobucket.com/albums/a24/accidentprone86/C7F4B84D-2086-43C6-A567-9A770C2091D9-185-00000011E5DB5373_zps080345da.jpg
Install was simple enough, will stake it if everything works out.
Tightening the adjustment screw all the way will completely close the key off.
I bought one, then immediately had buyers remorse because I just spent $70 bucks on a gas key.
Won't have time to mess with it for a few more weeks, though. I hope it works really well, and makes me not regret it.
Leaveammoforme
04-16-14, 23:46
Should we go ahead and get a sticky going about how to remove stripped gas adjustment screws? I'm gonna start building a jig to hold the gas key vertical for a drill press right now.
This seems so insanely obvious now that I've seen it :)
I agree with Ned that this looks like an excellent prototyping part. But even for fulltime use, I'm not seeing exactly unless maybe since it's lower pressure at the key, if you were to reduce the opening enough, perhaps a clog could form?
I'm highly anticipating some reviews. Ideally with full auto or highspeed cyclic rate testing and a 10,000 round+ test.
Eurodriver
04-17-14, 14:48
I'm not quite getting it.
As someone who has delved into dedicated suppressed SBRs with small gas ports and been in that mess for a long time, it seems too time consuming for use with a suppressor while also increasing the potential for problems.
And if you're buying this because your AR is horribly over gassed, for $70 you're half way to an LMT e carrier.
The LMT carrier is not adjustable, and you couldn't run a lightened carrier like jerrysimons (unless you do some machining)
Does the LMT enhanced carrier fix most overgassed barrels? I'm really curious because I got this DD barrel, which by all accounts is overgassed, so I ended up getting an adjustable gas block before I even tried it. But I like tinkering.
I'm interested in this, although even if it works, people will always wonder about reliability until it has been throughly tested.
If they made a drill-your-own port key, that should be as robust as the original.. Unless the chrome lining is needed all the way through..
The LMT carrier is not adjustable, and you couldn't run a lightened carrier like jerrysimons (unless you do some machining)
Does the LMT enhanced carrier fix most overgassed barrels? I'm really curious because I got this DD barrel, which by all accounts is overgassed, so I ended up getting an adjustable gas block before I even tried it. But I like tinkering.
I'm interested in this, although even if it works, people will always wonder about reliability until it has been throughly tested.
If they made a drill-your-own port key, that should be as robust as the original.. Unless the chrome lining is needed all the way through..
Welcome to the overgassed DD club! I have a 12.5", going on 1.5 years now, my sponsor has been DD Clean for 3 years, I hope to get there someday, one day at a time.
I have yet to see ANY testing that proves the LMT enhanced carrier actually reduces cyclic rate and by how much. I've tested and seen testing on Switchblock, Vltor A5, and MicroMOA... Nothing on LMT's carrier, I am betting it's a 5% change in rpm at most (bascially less effect than buffer-roulette). The only "testing" has been if it locks the bolt back or not in some guns which is a joke if you're looking for something even remotely scientific.
Does anyone else want a key? I thought I was clear with my offer of two free kits... Maybe my post was too long for someone to mow through it...
Leaveammoforme
04-17-14, 18:25
Does anyone else want a key? I thought I was clear with my offer of two free kits... Maybe my post was too long for someone to mow through it...
*Crickets*
Hilarious well one is now going to a member. One left...
jerrysimons
04-17-14, 19:01
Welcome to the overgassed DD club! I have a 12.5", going on 1.5 years now, my sponsor has been DD Clean for 3 years, I hope to get there someday, one day at a time.
I have yet to see ANY testing that proves the LMT enhanced carrier actually reduces cyclic rate and by how much. I've tested and seen testing on Switchblock, Vltor A5, and MicroMOA... Nothing on LMT's carrier, I am betting it's a 5% change in rpm at most (bascially less effect than buffer-roulette). The only "testing" has been if it locks the bolt back or not in some guns which is a joke if you're looking for something even remotely scientific.
Though a LMT technical rep told me in no unclear terms that I was wasting my money on the E-carrier if I wasn't running full auto on a long barrel w/ carbine gas system, it seems the e-carriers reduction on cyclic rate is its secondary benefit next to the revised cam pin track that allows chamber pressures to drop more before extraction begins, thus allowing the case to be removed with less friction against the chamber walls.
The extra venting capacity comes through the tiny weep hole, which vents the chamber directly behind the bolt tail/gas rings when the BCG is locked in battery and then the extra/third vent hole that is uncovered after the the bolt unlocks and the carrier is already in motion reward.
FWIW, my theory of the e-carrier is that as long as you have enough gas pressure to cycle it, the main benefit is the revised cam pin track. I don't know if this is 100% accurate but it does seem like either the e-carrier is quite modest in reducing gas pressure in the gas system or most guns are over gassed, or both.
Edit: OR since the e-carreir allows cases to be extracted with less work due to lower chamber pressures/friction against the case and chamber walls, and because the revised cam pin track allows the carrier to gain more velocity moving straight backwards longer before the cam pin is engaged laterally by the unlocking lobe in the track, the e-carrier can get away with venting more gas because it preforms less overall work.
Let's discuss a little about altering the cam path in the carrier. We can start really basic and proceed to more complex later.
Sullivan was mentioned a little earlier, he put together a project with others for multiple possible improvements in the platform. One of his improvements was a double cut in the cam way to increase carrier travel before the unlocking of the bolt begins. Basically keeping the same cam cut, and superimposing an identical cut offset to slightly increase the carrier stroke before the radial cut initiates cam pin/bolt rotation. Say we build a carrier that is otherwise 100% to the TDP, except this extended cut. Use this modified carrier, with all other TDP parts for their intended roles. 20" rifles, 14.5" and 10.5" carbines as a baseline that can be expanded somewhat later.
How do you suppose the characteristics would be in general?
During the action cycling sequence, the BCG would be able to travel further with only action resistance before initiating unlocking. That increased distance takes time and allows more pressure drop in the chamber, easing unlocking, and reducing stress on the bolt. What else is going on though? The initial travel with only action resistance allows the carrier to accelerate to a higher speed before unlocking. The added time decreases chamber pressure during unlocking, thus requiring less work to operate. With less work, the carrier speed isn't slowed as much as it would if it required the original work, again additional carrier velocity. So in general, during cycling, this would be a faster carrier.
How would this effect a 20" rifle? Out of the 3 rifle samples, the 20" should see the least gain in carrier velocity. It already unlocks at a reduced pressure than the carbines, plus has increased reciprocating mass over them. This would help keep the velocity increase to a minimum.
What about the 14.5" carbine? The original BCG was intended for 20" inch guns. When used in a 14.5", unlocking occurs during a higher chamber pressure than the 20". The system is gassed to give it more energy to cycle the action, as the the unlocking requires more work to be done. How does this effect the 14.5" with the altered carrier? There would be a larger jump in carrier velocity compared to the 20", as the system is gassed harder and has less reciprocating mass.
What about the 10.5" carbine? This would be more of the same as the 14.5", just even more of a carrier velocity than the others.
So, what could be done to reduce the speeds in these instances? Dedicated gas metering would probably be a good direction to look into, if it takes less work, you don't need as much gas obviously. There's other benefits of needing less gas, fouling being one of them. Another option on the carbines is to make their action system rifle like to keep the speed in check (think A5). Really a combination of the two is probably the best solution for carbines.
Let's chew on this for a little while.
see: https://www.m4carbine.net/showthread.php?163243-Bolt-Carrier-exhaust-vent-size-variations/page2
E-Man, I don't remember if you said already, are you planning on running the ADIGS on a e-carrier?
E-Man, I don't remember if you said already, are you planning on running the ADIGS on a e-carrier?
Yep - E-carrier Gen 5, was going to also run one on my MWS and one on a bone stock Colt 6920 but I don't have the time right now. I decided that rather then leaving two of these things sitting around in my parts collection for quite some time I would pass them on to other M4C members interested in testing and evaluating the first adjustable gas key on the market. I know another company is working on a similar system and with their name behind it people on here would jump at the chance to try one... (if it makes it to production)
I am still dubious as to how they changed the cam pin track. I have examined them very closely with another member and we cannot see a difference.
Though a LMT technical rep told me in no unclear terms that I was wasting my money on the E-carrier if I wasn't running full auto on a long barrel w/ carbine gas system, it seems the e-carriers reduction on cyclic rate is its secondary benefit next to the revised cam pin track that allows chamber pressures to drop more before extraction begins, thus allowing the case to be removed with less friction against the chamber walls.
The extra venting capacity comes through the tiny weep hole, which vents the chamber directly behind the bolt tail/gas rings when the BCG is locked in battery and then the extra/third vent hole that is uncovered after the the bolt unlocks and the carrier is already in motion reward.
FWIW, my theory of the e-carrier is that as long as you have enough gas pressure to cycle it, the main benefit is the revised cam pin track. I don't know if this is 100% accurate but it does seem like either the e-carrier is quite modest in reducing gas pressure in the gas system or most guns are over gassed, or both.
E-Man, I don't remember if you said already, are you planning on running the ADIGS on a e-carrier?
I am still dubious as to how they changed the cam pin track. I have examined them very closely with another member and we cannot see a difference.
Are you looking at them side by side sans gas keys?
I did the same with mine (without keys) when I first bought them and can see the slight changes, look at the right & left side channel from an overhead view with the carrier pointing away from you.
Here is a pic that shows it a little better...
https://lh5.googleusercontent.com/-SUAmrgY7BjQ/UrOLezw-JgI/AAAAAAAAGzg/oixnU82y0GI/s800/LMT_Enhanced_Bolt_FA_002.jpg
Compare that to a regular channel and you can see the "shoulder" the key contacts has been moved back a bit and the ledge made more abrupt while the opposite side appears more rounded. I don't think they did the revised channel right off of the bat though. I do have an email to LMT's engineering department to confirm some data I have complied to help everyone here detect what gen bolt / carrier they are looking at...
Anyways, you change your mind and want a key to try??? :D
jerrysimons
04-17-14, 21:19
In order top to bottom:
Jp low mass
Noveske
LMT E-carrier Gen 5
Noveske
http://i8.photobucket.com/albums/a24/accidentprone86/2557D470-9DA7-4F31-A2DB-F6DA1324613E-153-00000004D9057B47_zps2c932996.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/CF910BD4-625E-4292-A833-FABF2E1C905A-153-000000050408C7DF_zps782f7fcf.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/0592CCDC-5D43-4457-BD1A-3EBC92A738E4-153-0000000536F3155A_zps3f1b7e0a.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/A8FEF9B5-8DFB-4EBB-9E00-36838C70AA86-153-0000000672AAC637_zps8f2d3497.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/50E447C7-5C07-49F6-8BD6-508A2478EA0A-153-00000006BAB7118D_zpsd76dfd38.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/61770F14-A414-43C7-8A15-4A8482B2CD2A-153-00000006E838AFC3_zpsf67325a4.jpg
Track looks a little longer with a less abrupt bump to my eyes, staying locked longer and unlocking slower once it does start to twist the bolt.
If the cam track geometry is the main benefit of the e-carrier, the ADIGS key might be a welcome supplement to the concept of the e-carrier.
Wow you got a lot of flashlights! Can never have too many.
Nice pictures! Is it an illusion or does it look like the e-carrier locks up earlier too? (when going into battery)
Welcome to the overgassed DD club! I have a 12.5", going on 1.5 years now, my sponsor has been DD Clean for 3 years, I hope to get there someday, one day at a time.
Allright, there's a club!? I thought DD had a great rep too, just avoiding their barrels or other parts too?
I ended up going with a micromoa gas block, figuring the larger port would be fine for a SHTF scenario with the ability to switch ports at the push of a button.
E-man: I would take that key in for some testing, but figure someone more qualified will come along. I have little experience and am not sure if I'll put enough rounds through it to make it meaningful.. although I do already have an unstaked key on my colt carrier when I replaced the key that was slightly crooked.. colt clone 16" carbine. should make a good baseline test huh? :)
Id like to vBulletin try one.
Sent from my SGH-T989 using Tapatalk
Wormydog1724
04-17-14, 22:05
I'll put one in my sbr upper and can have 1000 rounds suppressed of wolf on it in a couple months time.
All spare keys are now gone. Gents, if you are getting a key, please put it through it's paces and report back here.
Holy shit. Captain Obvious wasn't so. I actually looked at it with the key off and didn't see it. Now it's making sense.
In order top to bottom:
Jp low mass
Noveske
LMT E-carrier Gen 5
Noveske
http://i8.photobucket.com/albums/a24/accidentprone86/2557D470-9DA7-4F31-A2DB-F6DA1324613E-153-00000004D9057B47_zps2c932996.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/CF910BD4-625E-4292-A833-FABF2E1C905A-153-000000050408C7DF_zps782f7fcf.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/0592CCDC-5D43-4457-BD1A-3EBC92A738E4-153-0000000536F3155A_zps3f1b7e0a.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/A8FEF9B5-8DFB-4EBB-9E00-36838C70AA86-153-0000000672AAC637_zps8f2d3497.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/50E447C7-5C07-49F6-8BD6-508A2478EA0A-153-00000006BAB7118D_zpsd76dfd38.jpg
http://i8.photobucket.com/albums/a24/accidentprone86/61770F14-A414-43C7-8A15-4A8482B2CD2A-153-00000006E838AFC3_zpsf67325a4.jpg
Track looks a little longer with a less abrupt bump to my eyes, staying locked longer and unlocking slower once it does start to twist the bolt.
If the cam track geometry is the main benefit of the e-carrier, the ADIGS key might be a welcome supplement to the concept of the e-carrier.
wrote something here, but really I don't know what I'm talking about. delete
Wormydog1724
04-25-14, 11:27
E-man, your inbox is full. Please delete so I can PM you.
hypercruiser
05-21-14, 21:26
Haven't seen any feedback on the adjustable key in use. Here is video of it on the Sun Devil Youtube channel :D (http://youtu.be/j0UknGFw__k?t=56s)
jerrysimons
05-21-14, 23:04
I finally got around to messing with the ADIGS.
The upper is a BCM midlength gas 14.5" ELW-F barrel w/ A2 flash hider and a JP QPQ low mass carrier w/ the ADIGS key.
The lower has a pistol carbine receiver extension w/ carbine buffer (same weight as JP low mass rifle buffer) and Springco blue spring. The trigger is a Giessele SD3G. Gun was cleaned and lubed with Fireclean.
I shot 160rds
80rds of 55gr .223 PMC Bronze
80rds of 55gr 5.56 Federal XM193
I am pleased with the adjustability of the system. First thing I did was close the key off to see what would happen. The carrier did not move as far as the naked eye could see and the minimal recoil felt was simply the equal and opposite reaction of sending the round down the barrel (forgot what kind of recoil this is called).
I shot a single round over and over in a pmag, periodically alternating between the .223 PMC bronze and 5.56 XM193.
I held the gun in three different ways to test the adjustability 1) loose in my hand/s. 2) pistol tube placed in the meat of my pectoral muscle 3) pistol tube placed with the end pressed against my collar bone. The distinction between the effects of 2 and 3 were important and became clearly distinguishable once I was fully conscious of what was happening.
I first adjusted to where the bolt would not lock back on empty when the buffer tube was placed against upper body using the 5.56 and then backed off 1/4 turn. It then locked back when placed against my upper body and when held loosely in my hand/s with the 5.56. Wanting to push it to the edge I restricted it 1/8th of a turn. The result using 5.56 was that the BCG would not lock back when the firearm was held loosely but would lock back when placed against my upper body.
At this point I switched to the .223 PMC. As expected with the lower pressure ammo, the BCG would not reliably lock back when placed against my upper body but perplexingly would every few shots. It was at this point that I realized how big the effect of placing the buffer tube against my collar bone was over placing it against my pectoral muscle. Over and over I was able to repeat the effect with the same gas setting above: with PMC .223 the BCG would lock back only when placed against my collar bone but not when placed in my pec muscle or when held loosely. SO, I backed it off 1/16th of a turn. Now the BCG would lock back when fired placed against my muscle and my collar bone, but not when held loosely. Then I opened it up another 1/16th of a turn to confirm it would lock back in all three firing positions with the PMC .223, and it did. Wanting to run the gun at the raged edge with the PMC .223 I restricted it back 1/16 of a turn and left it to where it would lock back when placed on either my collar bone or pectoral muscle but not when held loosely in the hand. At this setting with the higher pressure 5.56, however, it would lock back in all three firing positions.
One thing I wish I had tried and left for next time is using a high end .223 cartridge (Hornady match) and seeing where that gets me in comparison to the typically lower pressure PMC .223 and the standard 5.56. Also I would like to tinker with Tula but steel core is a no go at the indoor range I test at. Though PMC .223 will probably be the plinking round of choice for this gun so I left it tuned it to the edge with that ammo. All in all I am impressed with the function of the key, it worked as claimed in regulating the gas and is far easier to retrofit than an adjustable gas block. The one thing I am concerned about is if the screw is going to stay put in its current setting. I don't see how loctite is going to help much with out removing the screw to apply on the contact threads and then readjusting but time will tell if it holds simply by dripping some on the back of the screw. The new RCA version addresses this issue by having a second locking screw. The adjustments can be made then you place your loctite on the lock screw and tighten it on to the adjustment screw.
jerrysimons
06-20-14, 11:49
Looks like RCA has picked up Sun Devils design with some slight modifications: the second set screw to lock the adjustable screw in place, the radius cuts, and nitride finishing. $45 is a pretty good price IMO.
https://www.rubbercityarmory.com/ProdImages/adj_gas_key.jpg
https://www.rubbercityarmory.com/scripts/prodView.asp?idproduct=33
Made from Pre-Hardened 4140: 28-32RC with radiused corners reducing sharp edges.
Enhances performance of low mass and standard mass GI systems without unnecessary dissassembly. Gas flow is adjusted and maintained at the carrier with 2 set screws. One to adjust gas flow and one to lock it in place.
2 mounting bolts included.
I wonder if the expansion chamber characteristics could create reverse port erosion. I can't positively say this is a bad idea, but something just bugs me about allowing the excess gas into the tube in the first place.
I guess at one point I didn't trust Adjustable Gas blocks... now I couldn't do without one. It'll be interesting to see how these hold up.
I would be worried that the SunDevil Carrier Key will hit the charging, at the rear of the channel. Of all the charging handles we sell, the only ones that comeback broken is when the carrier key hits the end of the channel, which in turns breaks the latch. This is especially common when someone runs a carbine buffer in a A5 buffer tube. The RCA (Rubber City Armory) version has less of a chance of striking the handle.
ESK
I wonder if the expansion chamber characteristics could create reverse port erosion. I can't positively say this is a bad idea, but something just bugs me about allowing the excess gas into the tube in the first place.
I guess at one point I didn't trust Adjustable Gas blocks... now I couldn't do without one. It'll be interesting to see how these hold up.
Under no circumstances would I ever buy anything from Sun Devil. Much easier to light the cash on fire and avoid the pain and aggravation.
jerrysimons
06-20-14, 15:50
I would be worried that the SunDevil Carrier Key will hit the charging, at the rear of the channel. Of all the charging handles we sell, the only ones that comeback broken is when the carrier key hits the end of the channel, which in turns breaks the latch. This is especially common when someone runs a carbine buffer in a A5 buffer tube. The RCA (Rubber City Armory) version has less of a chance of striking the handle.
ESK
ESK, thanks for chiming in, the RCA version indeed looks like an improvement.
Can you comment on the technical efficacy of gas regulation at this point in the system? Anything that sticks out in your mind as far as pros or cons?
Thanks again.
BufordTJustice
06-23-14, 17:14
ESK, thanks for chiming in, the RCA version indeed looks like an improvement.
Can you comment on the technical efficacy of gas regulation at this point in the system? Anything that sticks out in your mind as far as pros or cons?
Thanks again.
I too would like to hear ESK opine on this.
The RCA gas key is something I might try on my wife's BCM.
Sent from my SPH-L720T using Tapatalk
Heavy Metal
06-23-14, 20:19
I am still dubious as to how they changed the cam pin track. I have examined them very closely with another member and we cannot see a difference.
It's shifted forward, takes a bit longer before it starts turning the cam pin allowing the chamber pressure to drop a bit.
I can see it easily when I look at it side by side with a standard carrier.
The reason they put the collar on the front of the carrier is to keep the extractor pin covered-up thru the full forward travel of the bolt, this was necessitated by shifting the cam track forward.
Heavy Metal
06-23-14, 20:29
IG, in those pics Jerry posted, look at the shelf where the lip of the charging handle engages Bolt Carrier. Notice how the front of the cam track is much closer to the charging handle ledge on the LMT E Carrier.
Looks like RCA has picked up Sun Devils design with some slight modifications: the second set screw to lock the adjustable screw in place, the radius cuts, and nitride finishing. $45 is a pretty good price IMO.
https://www.rubbercityarmory.com/ProdImages/adj_gas_key.jpg
https://www.rubbercityarmory.com/scripts/prodView.asp?idproduct=33
Made from Pre-Hardened 4140: 28-32RC with radiused corners reducing sharp edges.
Enhances performance of low mass and standard mass GI systems without unnecessary dissassembly. Gas flow is adjusted and maintained at the carrier with 2 set screws. One to adjust gas flow and one to lock it in place.
2 mounting bolts included.
Glad to see this - I attempted to give honest feedback to SunDevil and was ignored and basically told their key is "good enough as it is" when I mentioned another manufacturer was making a version that has the ability to lock the setscrew in place. Rubbercity would make the THIRD manufacturer to make one, the other company (a respected manufacturer) is still keeping quiet about their version.
I forgot - not to mention of the three SunDevil keys I received, all three had different tooling and machining marks along with differences in the dimensions... markm buddy, you were right.
Honestly, I not a fan of any restriction in the D.I. gas system. Any added restriction creates turbulence. Turbulence causes inconsistent pressure, which in turn creates inconsistent carrier velocities, which will affect accuracy and reliability.
Restricting gases right at the carrier key may starve the carrier’s expansion chamber from needed gases to operate properly. Without (or less) expanding gases in the carrier’s expansion chamber, the carrier may actually start opening sooner, lessening the needed dwell time. And, by lessening the needed gases in the carrier’s expansion chamber will take away the “floating bolt” feature during the unlock and extraction process. Also, this will probably cause excessive wear and stress on the carrier key and gas tube.
Eventhough I’m not a fan of any adjustable gas on a D.I. system, but if I was to develop a system, it would be at the gas block and not the carrier key. I’m a firm believer of regulating carrier velocity by regulating the reciprocating mass, i.e. BCG/Buffer weight and a proper spring rate.
Stoner’s D.I. system is extremely fine-tuned and very little is needed to disrupt the D.I.’s operating process.
That’s my two cents.
ESK, thanks for chiming in, the RCA version indeed looks like an improvement.
Can you comment on the technical efficacy of gas regulation at this point in the system? Anything that sticks out in your mind as far as pros or cons?
Thanks again.
BufordTJustice
06-24-14, 09:00
Honestly, I not a fan of any restriction in the D.I. gas system. Any added restriction creates turbulence. Turbulence causes inconsistent pressure, which in turn creates inconsistent carrier velocities, which will affect accuracy and reliability.
Restricting gases right at the carrier key may starve the carrier’s expansion chamber from needed gases to operate properly. Without (or less) expanding gases in the carrier’s expansion chamber, the carrier may actually start opening sooner, lessening the needed dwell time. And, by lessening the needed gases in the carrier’s expansion chamber will take away the “floating bolt” feature during the unlock and extraction process. Also, this will probably cause excessive wear and stress on the carrier key and gas tube.
Eventhough I’m not a fan of any adjustable gas on a D.I. system, but if I was to develop a system, it would be at the gas block and not the carrier key. I’m a firm believer of regulating carrier velocity by regulating the reciprocating mass, i.e. BCG/Buffer weight and a proper spring rate.
Stoner’s D.I. system is extremely fine-tuned and very little is needed to disrupt the D.I.’s operating process.
That’s my two cents.
Could the turbulence issue be a reason some gas block manufactures are using adjustment screws with conical tips? To prevent turbulence in the block?
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Eventhough I’m not a fan of any adjustable gas on a D.I. system, but if I was to develop a system, it would be at the gas block and not the carrier key. I’m a firm believer of regulating carrier velocity by regulating the reciprocating mass, i.e. BCG/Buffer weight and a proper spring rate.
I've had great results with my adjustable gas block. I've shot it a lot. The gun it's on wouldn't be saved by even an H4-A5 buffer, it was so massively over-gassed.... and that's BEFORE I put the can on.
You’re exactly right. The smoother the transition, the better off you are. Every time gas joint or elbow (such as a gas block and carrier key) is added into the mix, the more turbulence the gas flow encounters. The ideal system would have zero restrictions and smooth transition/radius elbows. Stoner achieved this on the AR10 and Stoner 62/63 programs, which he added radiuses as much as possible in gas selector valves and elbow. Less turbulence in a gas system will increase longer pressure times, with less pressure needed, meaning smaller gas port.
Could the turbulence issue be a reason some gas block manufactures are using adjustment screws with conical tips? To prevent turbulence in the block?
Sent from my SPH-L720T using Tapatalk
Could the turbulence issue be a reason some gas block manufactures are using adjustment screws with conical tips? To prevent turbulence in the block?
Sent from my SPH-L720T using Tapatalk
I'd argue that the cup tip adjustment screws are a COTS solution to a manufacturing/cost dilemma. While they may work sufficiently, a machined metering screw such as those used in the Syrac adjustable gas block clearly work better to meter the volume/time ratio of gas in the operating system.
Bluedreaux
06-25-14, 00:34
The DI system may be finely tuned in theory and design but it certainly isn't across the spectrum of what's actually being manufactured today, hence the need for adjustable gas.
What is it that this picture is illustrating as a difference? The length of the cam pin track rearward?
26779
The DI system may be finely tuned in theory and design but it certainly isn't across the spectrum of what's actually being manufactured today, hence the need for adjustable gas.
Exactamundo!! You have retards making already over-gassed guns so their booger eating customers can bump fire garbage ammo.... PLUS, Silencers are more and more popular which aggravates the already annoying problem.
What is it that this picture is illustrating as a difference? The length of the cam pin track rearward?
26779
Right. It also has a slightly different geometry than the standard carrier. If I recall, the LMT Enhanced carrier was originally designed for the M4 carbine gas system to help deal with the higher pressures and all the issues that come with it. Namely parts durability and system reliability. The basic idea was to delay unlocking the bolt to allow pressure to drop slightly before extraction.
Right. It also has a slightly different geometry than the standard carrier. If I recall, the LMT Enhanced carrier was originally designed for the M4 carbine gas system to help deal with the higher pressures and all the issues that come with it. Namely parts durability and system reliability. The basic idea was to delay unlocking the bolt to allow pressure to drop slightly before extraction.
Sitting here with a bolt group and barrel assembly in hand, I'd have to say that lengthening the track reward does nothing to delay extraction***. It appears to me the only way to mechanically delay unlocking would be to lengthen the area I'll refer to as the "delay flat" which is at the lower right of the track. To do this without extending the total length of the track forward would result in a very steep unlocking lobe in the tract (read more force). No matter what, the bolt has to be rotated 22.5 degrees before its lugs will clear the barrel extension. I think the difference in the track that we think see is a result of a dimensional differences between the location and size of the bearing rails on the bolt carriers. I'm not convinced there is a difference in track geometry on the LMT enhanced carrier (yet). I believe the vent hole at the back of the dust cover relief cut on the LMT enhanced bolt carrier is the special sauce.
For illustrative purposes only...
26781
ETA: ***The forward travel of the bolt group is arrested by contact with the barrel extension, not the cam pin. The length of the cam track reward is likely set by a required clearance between the cam pin and carrier.
would result in a very steep unlocking lobe in the tract (read more force)
That's the part that bugs me a little.
BufordTJustice
06-25-14, 12:53
Mark, the LMT cam pin track is longer. Look at the front of the cam pin track relative to the ridge on the forward portion of the carrier key. The LMT's cam pin track is clearly longer than the others.
Sitting here with a bolt group and barrel assembly in hand, I'd have to say that lengthening the track reward does nothing to delay extraction***. It appears to me the only way to mechanically delay unlocking would be to lengthen the area I'll refer to as the "delay flat" which is at the lower right of the track. To do this without extending the total length of the track forward would result in a very steep unlocking lobe in the tract (read more force). No matter what, the bolt has to be rotated 22.5 degrees before its lugs will clear the barrel extension. I think the difference in the track that we think see is a result of a dimensional differences between the location and size of the bearing rails on the bolt carriers. I'm not convinced there is a difference in track geometry on the LMT enhanced carrier (yet). I believe the vent hole at the back of the dust cover relief cut on the LMT enhanced bolt carrier is the special sauce.
For illustrative purposes only...
26781
ETA: ***The forward travel of the bolt group is arrested by contact with the barrel extension, not the cam pin. The length of the cam track reward is likely set by a required clearance between the cam pin and carrier.
jerrysimons
06-25-14, 13:13
Sitting here with a bolt group and barrel assembly in hand, I'd have to say that lengthening the track reward does nothing to delay extraction***. It appears to me the only way to mechanically delay unlocking would be to lengthen the area I'll refer to as the "delay flat" which is at the lower right of the track. To do this without extending the total length of the track forward would result in a very steep unlocking lobe in the tract (read more force). No matter what, the bolt has to be rotated 22.5 degrees before its lugs will clear the barrel extension. I think the difference in the track that we think see is a result of a dimensional differences between the location and size of the bearing rails on the bolt carriers. I'm not convinced there is a difference in track geometry on the LMT enhanced carrier (yet). I believe the vent hole at the back of the dust cover relief cut on the LMT enhanced bolt carrier is the special sauce.
For illustrative purposes only...
26781
ETA: ***The forward travel of the bolt group is arrested by contact with the barrel extension, not the cam pin. The length of the cam track reward is likely set by a required clearance between the cam pin and carrier.
The "unlocking-lobe" is less pronounced on the e-carrier. This is the other dimensional difference I attempted to point out. In your words I would say that the "delay flat" is longer.
Jerry - Can you measure the width and depth of the flat on the top/front of the LMT carrier along with its overall length?
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Wormydog1724
06-25-14, 20:18
I've put 600 rounds through mine, 60 without a can.
10.5" PSA upper, FSB. Spike's T2 buffer and spring. M4-2000 suppressor.
60 rounds of Wolf .223 without a suppressor.
Set it 3 full turns form completely off, ran fine and soft. Locked back on last round.
Set it 2 full turns from completely off, would not cycle.
Set it 2.5 turns from completely off. Ran fine and soft and locked back. Didn't move it again.
Put the can on and continued to fire 540 more rounds, taking extended breaks in between, sometimes up to days. No more than 60 rounds back to back. All Wolf .223.
With the can on, it was over gassed. Not as bad as before mind you, but since it ran without the can, I didn't feel the need to adjust it anymore.
One thing I did notice, there was FireClean coming out around the FSB. My guess its being forced backwards down the gas tube. I did have one stuck case and several misfeeds, I am attributing this to shitty ammo and shitty GI mags I bought with god-knows how many rounds through them.
http://i416.photobucket.com/albums/pp247/wormydog1724/2014-06/EE034C31-04D2-485B-9393-26D887DDF656_zpsydebryrp.jpg
One thing I did notice, there was FireClean coming out around the FSB. My guess its being forced backwards down the gas tube.
That would be the end of that gadget, right there, for me. Wow. That intermediate expansion between the port and the key... and then the expansion in the carrier? Just doesn't seem bueno.
Wormydog1724
06-26-14, 09:07
That would be the end of that gadget, right there, for me. Wow. That intermediate expansion between the port and the key... and then the expansion in the carrier? Just doesn't seem bueno.
My thoughts exactly. I love my syrac gas blocks but so far this doesn't do it. The bcg is still over gassed with the can on and I don't see how the adjustable key can fix that. Adjustable gas block seems to the be best solution.
Thanks for the testing WD, we appreciate it.
Wormydog1724
06-26-14, 11:49
Thanks for the testing WD, we appreciate it.
I'll have more input as time progresses. But right now I'm not loving it.
I put a Rubber City Armory adjustable gas key on one of my rifles. It uses two set screws in the same hole, the second acting as a lock nut to the first. I'm not super excited about this setup, we'll see how it works.
The rifle I have it on is a dedicated suppressed rifle with a shaved forged front sight post that's taper pinned. The barrel is an FN made Spikes hammer forged chrome lined 16 inch medium contour.
The suppressor is an older AWC can that basically has fender washers in it. It's low tech, but pretty quiet on the 16 inch barrel. As I hoped, the adjustable gas key quieted the rifle down from the shooters perspective, as it cuts down on the gas coming out of the bolt carrier gas ports. The instructions said to start with it backed off 1/2 turn from 'closed' (which I don't think shuts off the gas), and back it off 1/4 turn at a time until it locks back on the last round. Mine locked back and still felt over gassed, so I went the other way.... and it still locked back, but the ejection felt a lot softer. I think next time I shoot it, I'll dial it all the way down and see if it will still lock back.
The workmanship on it is amazing, it looks melonited, and is a very good looking bit. I'm a little worried about the screws, but if I have a problem I'm sure I can replace them. This rifle will always have it's suppressor on, so I'm not trying to get it to balance out between suppressed and unsuppressed... as long as it doesn't fail, I'll be a happy camper.
http://i39.photobucket.com/albums/e200/eodinert/guns/2014-05-16100858_zpsaa150a15.jpg
Two more Gen5 Enhanced differences not evident lit from inside. At least different from standard LMT FA and Fail Zero I had handy to compare. First, rear edge of opening facing gas key is sharply beveled. Second, peak of shoulder also has a sharply defined facet.
How does that facet at the peak affect cam pin travel? My first thought is that the fore and aft ridges would bounce the pin, but i'm admittedly ignorant of the principles involved so need to be schooled on the facet's benefit.
http://i150.photobucket.com/albums/s92/uffdaphil/imagejpg1-31.jpg (http://s150.photobucket.com/user/uffdaphil/media/imagejpg1-31.jpg.html)
http://i150.photobucket.com/albums/s92/uffdaphil/imagejpg2-8.jpg (http://s150.photobucket.com/user/uffdaphil/media/imagejpg2-8.jpg.html)
jerrysimons
01-02-15, 09:53
E-man,
Did you get around to running this part? Sorry if you posted your results already and I missed it.
Magic_Salad0892
01-03-15, 12:11
I missed this thread months ago. Glad it got bumped so I could catch it.
Anybody get 10k on theirs, yet?
jerrysimons
01-03-15, 19:17
This thread is definitely interesting pertaining to the discussion of regulation at the gas-key: https://www.m4carbine.net/showthread.php?163243-Bolt-Carrier-exhaust-vent-size-variations
How would the FireClean get back up the gas tube? Pulling it from the BCG under vacuum in the barrel while the gas-tube is still pressurized due to the restriction?
Unfortunately I have not tested this setup any further. I did replace the JP low-mass w/ Sun-Devil key for an RCA key on a Boomfab Ti carrier. But this project is stalled out for the time being awaiting parts and funds.
I've been running Rubber City Armory's adjustable gas key for a few months now, and I'd rate it very successful. I have one mid-length that would not smooth out: tried different action springs, buffers from carbine to H3, different ammo, no luck. Put the RCA AGK on, tuned it per instructions on my favorite handload (M193 equivalent), and voila! Settled right down. The only subsequent adjustment was for low-powered ammo (Herter's/Tula), which would not lock back on the last round; 1/4 turn more gas, and bingo! That gun has probably 500 rounds down the pipe since install, and nothing has changed or come loose. I know it's not a mil-grade evaluation for durability, but it's a data point for any of you considering adjustable gas retro-fit. HTH
https://www.rubbercityarmory.com/scripts/prodView.asp?idproduct=33
E-man,
Did you get around to running this part? Sorry if you posted your results already and I missed it.
No I ended up sending out all of the keys I had purchased as free samples for M4C members to try and report back...
E-man
Sparky5019
01-28-15, 21:32
Any more info from extra rounds? WormyDog, any worsening of that FireClean coming from under the FSB? I just installed one for a customer so I'm interested in any news. Thanks y'all!
Rayrevolver
05-21-15, 21:50
Sorry to bump this thread...
Just thinking about another solution. If the thought process is that choking the gas flow at the gas block is better, why not sell a gas tube with a smaller diameter hole? The end user would then drill the hole bigger and bigger until you got what you wanted. You can keep your pinned FSB and BCG as-is.
Anywho, I might get a Rubber City to try since it is the cheaper of the options vice ADIGS or Gemtech BCG or E-Carrier. If anyone knows where you can get gas tubes without holes drilled, that would be cool also.
I bought several of these to try also. First one was for a 16" BA Hanson midlength gas, but they did a great job on factory sizing, it was only .068" hole size and super light on recoil already so I skipped this build. I installed on a budget $95 Low Mass BCG and ran it in my 12.5" Compass Lake that has a Form 1 Reflex suppressor. Great improvement on blowback, the most pleasant suppressed SBR I have every shot. The set screw at only 1/8-1/4 of a turn from completely closed allows it to cycle suppressed but not lock back on an empty mag. Between 1/4-1/2 of a turn it functions completely. I opened it a little more than this. Other Key went in a 11.5" DD LW.
Video of adjusted and unadjusted. Doesn't really show much but it is quieter at the shooter's ear.
https://www.youtube.com/watch?v=N9AILLCVjMo
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