I have several carbine length gas seystem AR uppers in 5.56 with A-2 sight towers

Tired of dented brass and 1 o'clock ejection I purchased a Ruber City Armory adjustable gas key and installed it on an M16 bolt

Simple instructions supplied with the key were simple/very easy to follow and after the 4th round the rifle ran the rest of the day without a single issue

Ejection is now 3 o'clock

As a DIY project I decided to make my own adjustable gas key

I pulled a gas key off of an M16 bolt and Rockwell tested it......26C

I set it up in a mill and simply drilled and tapped 8-32 into the same location as the Ruber City Armory key

Installed 2 set screws and proceeded to get the same great results from this DIY key as the store bought

Ted,
While we may agree to disagree on he utility of such an arrangement, I applaud your sense of experimentation. We in high power competition with the AR have long adjusted ejection by either trimming a coil or two off the ejector spring or by shortening/angling the face of the ejector. As to adjusting the operating force of the system, we use separately or in conjunction with each other stiffer springs or adding a carrier weight.

With 20 inch or longer barrels and standard or extended port locations, custom port diameters etc we achieve extended brass life with heavy loads ( ~25 grn charges/80 grn bullets), less violent cycling and more convenient extraction/ejection of spent brass.

Carbines are apt to have the worst of all conditions simply by virtue of the greater port pressures due to the shorter port location (standard port pressure is supposed to be ~8k psi, carbine pressures run ~20k with ball ammo per USG testing).

Kudos to you for your effort.

Yes the 7" gas length of these rifles make a tough tune.

I have gone the route of the heavy spring or the flat wire SSS

Heavy buffers of solid Beryllium and M16 bolts

These simple adjustable keys did what all these should have in short order

Combat use? Heck no!!

Range banging steel gongs and trying to control ejection.....yes

Ted;

I was involved in some research post Army that looked t how the M4 basically halved the service life of the weapon due to excessive impulse in cyclic mechanics. Even going to a mid-length port distance yielded much less wear and tear. One Ordnance type speculated that it was better to have more force/impulse than required in a combat situation due to more certain function (over gassed= more reliability in his mind). I casually mentioned that the weak link was not the rifle, but the cartridge case. In hot testing (heated ammo/gun) we found that the extraction forces often well exceeded the manufacturing specs of the cartridge brass extraction groove ( head). He smiled and said, "oh, I didn't think of that, can we switch to steel?".

With operating pressures in the realm of 63500psi, adding 130 f heat to both gun ad ammo often ( lot dependent) pumped pressures well over 65, 67, even 69k psi.

Th best solution mechanically found by the Army research Lab (ARL) was adding carrier weight to increase dwell time and slow cyclic rate (they tested the Tubb CWS, I use one in my Service Rifle) while conserving energy-flat wire CS/ heavy duty springs and added weight equaled the same force, but slowed the mechanism both at onset/primary extraction t and at locking- reducing risk o tor extraction rings substantially.

None of the recommendations we made were ever implemented. Even at its worst, the M4 is rather reliable and robust. Compared to the M14 series, using meta data, the M4 I about 2x more reliable than the venerable 14. A requirement of over 8k rounds between failures (not stoppages- a magazine issue often, necessarily) is rather high.