Gas Tube Blues

[tdbru]

i thought i read a long time ago, that the ball powder being used in 223 ammo in Vietnam had a high calcium carbonate content. i guess that is a flash suppressor?? not sure, any way i heard antidotal stories that the calcium carbonate would plate out in the gas tube and eventually cause failures to cycle due to plugging up the gas tube. when they went to different powder the problem went away. i also read somewhere that Eugene Stoner intended the gas system design to use cartridges with stick powder, not ball powder for that reason. Since the AR gas system issues have been well sorted out now, in the almost 60 years since the AR's adoption, i wouldn't expect stoppages due to plugged up gas tubes anymore. in line with the OP question, i am curious if anyone has recently ended up with failures to cycle due to not cleaning out the carbon in either the gas tube or the bolt carrier expansion chamber? other than liking things clean, has it ever caused a malfunction? i haven't used my first build much, since i haven't had a lot of time off of work, but i also haven't yet cleaned the gas tube or the BCG expansion chamber. and if i don't have to, for functional reliability, i may not bother. on the other hand if not cleaning these out does indeed cause malfunctions down the road, then i'll have to put it on a maintenance schedule at x number of rounds.
thanks,
-tdbru

[CJW]

Interesting tdbru

[A5BLASTER]

i thought i read a long time ago, that the ball powder being used in 223 ammo in Vietnam had a high calcium carbonate content. i guess that is a flash suppressor?? not sure, any way i heard antidotal stories that the calcium carbonate would plate out in the gas tube and eventually cause failures to cycle due to plugging up the gas tube. when they went to different powder the problem went away. i also read somewhere that Eugene Stoner intended the gas system design to use cartridges with stick powder, not ball powder for that reason. Since the AR gas system issues have been well sorted out now, in the almost 60 years since the AR's adoption, i wouldn't expect stoppages due to plugged up gas tubes anymore. in line with the OP question, i am curious if anyone has recently ended up with failures to cycle due to not cleaning out the carbon in either the gas tube or the bolt carrier expansion chamber? other than liking things clean, has it ever caused a malfunction? i haven't used my first build much, since i haven't had a lot of time off of work, but i also haven't yet cleaned the gas tube or the BCG expansion chamber. and if i don't have to, for functional reliability, i may not bother. on the other hand if not cleaning these out does indeed cause malfunctions down the road, then i'll have to put it on a maintenance schedule at x number of rounds.
thanks,
-tdbru

This is what I can tell you from my personal experience with 3 AA 16 inch fluted barrels so far.

No matter if it has been factory or handloads are a combination of both. I have on several occasions ran the round count up past 500 rounds without cleaning and have yet to have a issue due too a dirty gas tube are because of a dirty bcg.

I make a habit of doing a strip cleaning at are around 500 rounds. But honestly feel on a function aspect I could go much longer without having to worrie about a issue.

I believe being properly gassed and good quality parts used are more important then cleaning X amount of rounds.

As too the question of cleaning the gas tube. I have never thrown away a gas tube I just keep reusing them, moving them from gas block to gas block and barrel to barrel. I have blown some air in it from my air compressor in the shop between moves that about it.

[CJW]

I’m in the habit of strip cleaning every 300 rounds......

I am always amazed at how little copper comes out of both my Grendel barrels.

The BCG is filthy, but that gets filthy after 10 shots.

The AR15 is simply an amazing gun........

[tdbru]

thanks guys for the replies. sounds like even cleaning out the expansion chamber in the bcg and the tail of the bolt may not be required for a long time. that's good news to a time constrained person.
-tdbru

[LRRPF52]

i thought i read a long time ago, that the ball powder being used in 223 ammo in Vietnam had a high calcium carbonate content. i guess that is a flash suppressor?? not sure, any way i heard antidotal stories that the calcium carbonate would plate out in the gas tube and eventually cause failures to cycle due to plugging up the gas tube. when they went to different powder the problem went away. i also read somewhere that Eugene Stoner intended the gas system design to use cartridges with stick powder, not ball powder for that reason. Since the AR gas system issues have been well sorted out now, in the almost 60 years since the AR's adoption, i wouldn't expect stoppages due to plugged up gas tubes anymore. in line with the OP question, i am curious if anyone has recently ended up with failures to cycle due to not cleaning out the carbon in either the gas tube or the bolt carrier expansion chamber? other than liking things clean, has it ever caused a malfunction? i haven't used my first build much, since i haven't had a lot of time off of work, but i also haven't yet cleaned the gas tube or the BCG expansion chamber. and if i don't have to, for functional reliability, i may not bother. on the other hand if not cleaning these out does indeed cause malfunctions down the road, then i'll have to put it on a maintenance schedule at x number of rounds.
thanks,
-tdbru

It is true that the AR15 was engineered around small stick powders, one of which was 8208M at the time.

However, the problems experienced early with the AR15's fielding in Vietnam were a result of several things:

* The Colt Model 602 AR15 was mass-produced with reamer variances that ranged from satisfactory to way too tight of chambers, while the first Model 601 guns were fine (The Green Rifle).
* The chamber was not hard come-plated.
* Cleaning kits were not specified or issued to soldiers.
* The new lots of ammunition were loaded with ball propellant, instead of stick powder because they had a hard time maintaining consistent burn rates with the tiny sick powders in extreme high volume production for the Army and USMC demand. Rifles were tested and benchmarked for production spec sign-off by DoD using the known-performer stick powder ammo, then sent to Vietnam and fed the unknown, ball propellant ammo. Gas port pressures with the ball propellant ammo increased to well over 10,000psi, far outside of the timing window for the cycle of operation.
* The humid tropical climate of Vietnam caused quick chamber erosion.



Combine a tight chamber, corroded/rough-textured chamber, with no cleaning kits/limited lubrication, and extreme high port pressures and you get Failure To Extract all day long, regardless of what design the rifle is. Those RO602 AR15s would FTEx, including case head separation, with no broken shell extractors issued, let alone cleaning kits with bore and chamber brushes.

There were 2 USMC officers or senior NCOs that wrote letters back to their Congressmen telling them about how the AR15 was getting guys killed, how they were scrounging for enemy weapons to issue out, costing them their careers. Congress held hearings on it with the Ichord Subcommittee, and found out a lot of the dirty laundry of how the program was mismanaged.

The result largely entailed things the Army was already working on, but manifest all the corrections with the Colt Model 603, otherwise known as the M16A1.

The best features that corrected the problems were:

* Hard Chrome chamber and later bore
* Maintain spec on the chamber reamers so that you don't go below minimum chamber
* Addition of the heavier buffer, replacing the Edgewater Spring Guide
* Issue of cleaning kits with sectional rod, bore brushes, and M16-specific chamber brush, with oil bottles



The unnecessary and retarded feature they added that Stoner recommended against and the USAF refused to adopt for their rifles was the Forward Assist Assembly. The Army had an infatuation with the Forward Assist, thinking that it was the panacea of helping chamber rounds that didn't want to be chambered. In reality, a lubed M16A1 ran like a raped ape and never needed Forward Assist, but it made some engineers in the Army Ordnance Board feel warm and fuzzy inside, so it became standard.

The USAF got their own rifle nomenclature and Model as a result, separate from the Army, with the Colt RO604. USAF Special Operations personnel used slick side Carbines as well, and the Son Tay Special Forces Raiders used the USAF GAU-5A/A carbines for their extensive training and execution of the Son Tay Raid in 1970.

Anyway, I've shot insane amounts of 5.56 NATO and 6.5 Grendel over the years, as well as 7.62 NATO and .260 Rem through gas guns. I've never cleaned a gas tube inside other than to hide some of the carbon residue near the end of the tube with pipe cleaners before ORS inspections in the Army, and the only reason for that was to pass the monstrously-stupid white-glove inspections where all the CLP was stripped of the weapons to make them bone-dry so that senior leaders with zero understanding of weapons maintenance and basic materials science can be happy with the cleanliness (and lack of functionality) of the weapons in their assigned inventories.

The TMs specifically forbid the insertion of Q-tips into the gas tube, as soldiers subjected to white glove inspections have clogged their gas tubes with little compressed cotton balls that way, which will turn the rifle into a single shot.

[CJW]

Very, very interesting PF52....

[tdbru]

interesting history. as an aside, is it possible to get a slick side upper yet? does anyone make them? the forward assist seems to be a feature that is indeed not needed if everything is clean and lubed. i know some may argue that having it and not needing it doesn't hurt anything. other than adds weight to an already overweight rifle. anyway, LRRPF52, that reply was highly educational and appreciated. thank you.
-tdbru

[phishfood]

I have a 2A Arms slick side upper on my Grendel, and I believe Aero Precision makes one as well. Probably others available.

Edit to add: I have a 5.56 blaster rifle with a high round count. I have gotten it so filthy that rounds didn't want to go into the chamber, but only maybe once did I manage to pound a round in with the forward assist and get it to fire. I have had a lot better luck aggressively cycling the action when it gets sticky. .

[Kswhitetails]

CMMG makes one they sell over at midway. No dust cover either, and it's not close to mil spec dimensions. Heavy. Really good for a target gun.

I believe ZEV makes a forged upper without a FA, also a billet version. Be prepared, most expensive forged uppers I recall seeing.

[A5BLASTER]

interesting history. as an aside, is it possible to get a slick side upper yet? does anyone make them? the forward assist seems to be a feature that is indeed not needed if everything is clean and lubed. i know some may argue that having it and not needing it doesn't hurt anything. other than adds weight to an already overweight rifle. anyway, LRRPF52, that reply was highly educational and appreciated. thank you.
-tdbru

I believe just about every company that has their name are logo on a upper has a forged and possible a billet slick side upper.

[LRRPF52]

interesting history. as an aside, is it possible to get a slick side upper yet? does anyone make them? the forward assist seems to be a feature that is indeed not needed if everything is clean and lubed. i know some may argue that having it and not needing it doesn't hurt anything. other than adds weight to an already overweight rifle. anyway, LRRPF52, that reply was highly educational and appreciated. thank you.
-tdbru

Yes, and that's what I used on my 17.6" Lilja barrel Grendel. It's an No-Forward Assist "M4" upper from Aero Precision with a keyhole forge code.




No reputable instructor teaches to use the Forward Assist for clearing malfunctions, and AFSOC didn't have them on their weapons for 4 decades.

In the regular Army, they taught this stupid malfunction clearance procedure called SPORTS instead of "Tap, Rack, Bang" like they should have.

There's also a retired Army General who was Artillery that makes his rounds as an expert on small arms, often citing failures with the M16 in combat when enemy units tried to overrun his unit's position in Vietnam, after admitting that they didn't enforce any weapons maintenance standards in that unit, and that his guys were asleep.

He said one of the main failure points of the M16/M4 is its aluminum gas tube, just to give you an idea of his familiarity with the weapon. It's embarrassing to see him talk or write about small arms. General Scales...

[tdbru]

LRRPF52, what is a keyhole forge code?? pardon my ignorance. i like the looks of that upper. is it possible to get it without the forward assist and without the brass deflector? it be a bit narrower and would likely fit in scabbards or cases just a bit easier.
-tdbru

[Lastrites]

The "keyhole forge code" is simply the manufacturer's mark/imprint of who originally forged the upper prior to final machining. It is shown in his picture about an inch below the rail directly above the word "safe".