View Full Version : I learned something new (to me) about the AR
So, for my first post here I thought I would share a story that embarrassed me a bit, having owned AR's as long as I have. Just when I thought I knew all there was to know aside from the newly manufactured stuff, I was humbled. Isn't life grand that way?
I never knew that if the gas tube overheated to melting, the rifle could still be operated as a bolt action using the charging handle.
Maybe everyone knew that and I'm just the village idiot(I'll take it), but perhaps it'll be a learning opportunity for someone else.
Since we're at it, have you discovered something about the AR that you should've known about?
bamashooter
05-16-21, 07:08
Likely some AR owners users know this but more likely the vast majority of AR owners do well to fire the sob (imo).
The Dumb Gun Collector
05-16-21, 10:07
I don't think I knew that either but it does make sense.
It never crossed my mind, but yea I guess it would. You might have some nasty burns on your hand though.
Not a critique of the OP, but every video I've seen where the M4/AR was shot to failure it was the barrel that let go before the gas tube. Maybe I've just not seen enough video of these kinds of things.
Not a critique of the OP, but every video I've seen where the M4/AR was shot to failure it was the barrel that let go before the gas tube. Maybe I've just not seen enough video of these kinds of things.
Ive definitely seen the gas tube rupture during destructive testing videos. I cant remember if it was Colt's video or one done by IV8888 though.
Here is the Colt test I was talking about. I cant find the original video. The gas tube ruptures around 4:25 in the video and he shoots several rounds bolt action style after.
https://www.youtube.com/watch?v=Kzfm4pYhIyY
MrGunsNGear did a melt down and the gas tube ruptured at 1075ish rounds.
https://www.youtube.com/watch?v=_WD0W4ry0LY
Had no idea that was possible
If more people dry fired, this would be more instinctive...
Malfunction clearances are the same way, and believe me, I should be doing more of both. The only reason I'm here (alive) is because of malfunction clearance training and drills.
I knew that but I've seen pump action ARs and AKs. Not to mention LARPing.......i mean dry fire. ....with my first AK when I was 19!!!!! Ahh the carefree days!!!
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I saw a post years back by a newb saying that he knows the gas tube is the single most important part on the M4; so how often should he clean it. That got my mind into thinking about the mechanics and I realized back then what the op is saying.
I would just make sure the gas block is removed or something is in the gas tube hole of the gas block so fire does not come back towards the shooters face.
Lastly I came to my own conclusion that the gas tube is certainly NOT the single most important part. You need a barrel before anything else. Think about it, you could jam a round into a bare barrel and set it off with a hammer and a nail. Shoot, just rock and a nail.
Here is the Colt test I was talking about. I cant find the original video. The gas tube ruptures around 4:25 in the video and he shoots several rounds bolt action style after.
https://www.youtube.com/watch?v=Kzfm4pYhIyY
Thanks.
My biggest AR surprise came when I started handloading for them. The design is amazingly tolerant of pressure levels and different powders. It seems that any reasonable load with mid burn rate powders will cycle the gun just fine, at least in "going to the range" temps. I remember reading how a simple switch from stick to ball powders (or vice-versa) caused huge reliability problems in VN and my experience certainly does not bear that out (admittedly the AR has changed a bit since then too).
Compare that to loading for a stock Garand - very narrow range of allowable powders and pressure.
Andy
Here is the Colt test I was talking about. I cant find the original video. The gas tube ruptures around 4:25 in the video and he shoots several rounds bolt action style after.
https://www.youtube.com/watch?v=Kzfm4pYhIyY
That is actually a Rock Island Arsenal Test of the (then) new heavy barrel.
MountainRaven
05-18-21, 22:30
My biggest AR surprise came when I started handloading for them. The design is amazingly tolerant of pressure levels and different powders. It seems that any reasonable load with mid burn rate powders will cycle the gun just fine, at least in "going to the range" temps. I remember reading how a simple switch from stick to ball powders (or vice-versa) caused huge reliability problems in VN and my experience certainly does not bear that out (admittedly the AR has changed a bit since then too).
Compare that to loading for a stock Garand - very narrow range of allowable powders and pressure.
Andy
The AR is a lot more tolerant of things when fired semi-auto only than when fired full-auto. Add that to a high humidity, high temperature environment that's intrinsically hostile to everything man-made... Increased cyclic rate, plus increased gas port erosion (due to both firing schedule and possibly corrosion), plus full-auto, plus hostile environment... and now your gun may not work as well as it should. Add neglect due to a lack of available cleaning kits and components. Plus the fact that Colt may or may not have been making guns to a consistent level of quality and there may or may not have been a fixed TDP for the XM16E1... Problems on problems on problems.
The Garand, being a gas trap rifle that was adapted to long-stroke piston, has very short dwell-time, with the gas port being located about an inch from the muzzle.
(On the subject of allegedly very tolerant gas systems: The short-stroke gas piston system. The FN FAL has one, but it has eleven adjustment settings on it and the difference between 1 and 11 is the difference between the gun barely functioning or not functioning at all and the gun beating itself to bits. But an AR with a short-stroke piston is supposed to be entirely self-regulating and über-reliable. And some of them are absolutely, but I question whether the increased reliability is really there.)
I saw a post years back by a newb saying that he knows the gas tube is the single most important part on the M4; so how often should he clean it. That got my mind into thinking about the mechanics and I realized back then what the op is saying.
I would just make sure the gas block is removed or something is in the gas tube hole of the gas block so fire does not come back towards the shooters face.
Lastly I came to my own conclusion that the gas tube is certainly NOT the single most important part. You need a barrel before anything else. Think about it, you could jam a round into a bare barrel and set it off with a hammer and a nail. Shoot, just rock and a nail.
"Bolt action" ARs have been around for a long time, mostly because of semi auto centerfire laws in GB. All they are is ARs without a gas port in the barrel and normally will use a side charging upper of some sort. Otherwise they're all stock AR.
The AR is a lot more tolerant of things when fired semi-auto only than when fired full-auto. Add that to a high humidity, high temperature environment that's intrinsically hostile to everything man-made... Increased cyclic rate, plus increased gas port erosion (due to both firing schedule and possibly corrosion), plus full-auto, plus hostile environment... and now your gun may not work as well as it should. Add neglect due to a lack of available cleaning kits and components. Plus the fact that Colt may or may not have been making guns to a consistent level of quality and there may or may not have been a fixed TDP for the XM16E1... Problems on problems on problems.
The Garand, being a gas trap rifle that was adapted to long-stroke piston, has very short dwell-time, with the gas port being located about an inch from the muzzle.
(On the subject of allegedly very tolerant gas systems: The short-stroke gas piston system. The FN FAL has one, but it has eleven adjustment settings on it and the difference between 1 and 11 is the difference between the gun barely functioning or not functioning at all and the gun beating itself to bits. But an AR with a short-stroke piston is supposed to be entirely self-regulating and über-reliable. And some of them are absolutely, but I question whether the increased reliability is really there.)
Technically, "DWELL TIME" is the time from primer ignition to bolt unlock.
The AR community has been misusing the term for some time.
As to the FAL, the reason its gas system goes from the two extremes is it uses a "bleed on" gas system as opposed the "bleed-off" system almost everyone else used with adjustable gas porting.
Technically, "DWELL TIME" is the time from primer ignition to bolt unlock.
The AR community has been misusing the term for some time.
As to the FAL, the reason its gas system goes from the two extremes is it uses a "bleed on" gas system as opposed the "bleed-off" system almost everyone else used with adjustable gas porting.
Seriously? I always felt intuitively like that terminology was backwards. Do you have a source for that?
CLARIFICATION: Dwell time is from ignition to the beginning of unlocking.
Seriously? I always felt intuitively like that terminology was backwards. Do you have a source for that?
Every text book on automatic weapons design written since the 1930s . . .
But, here's just one example from a 1954 report:
https://i.imgur.com/F50wJEg.png
Not a critique of the OP, but every video I've seen where the M4/AR was shot to failure it was the barrel that let go before the gas tube. Maybe I've just not seen enough video of these kinds of things.
I was under the impression that the gas tube was intended to pop before the barrel melted down. I'm sure there are people that know a lot more about the subject that can correct me if that's wrong.
I was under the impression that the gas tube was intended to pop before the barrel melted down. I'm sure there are people that know a lot more about the subject that can correct me if that's wrong.
Actually, no.
With the lightweight M16 or M4 barrel (~3/4 to 5/8" diam under the handguards) the barrel will rupture before the gas tube in sustained full automatic fire. It takes around 3 minutes/500 to 600 rounds.
CLARIFICATION: Dwell time is from ignition to the beginning of unlocking.
Every text book on automatic weapons design written since the 1930s . . .
But, here's just one example from a 1954 report:
https://i.imgur.com/F50wJEg.png
Right on. That just never did sound right to me, and now I know why!
Actually, no.
With the lightweight M16 or M4 barrel (~3/4 to 5/8" diam under the handguards) the barrel will rupture before the gas tube in sustained full automatic fire. It takes around 3 minutes/500 to 600 rounds.
What about the current M4 profile barrels?
I saw a post years back by a newb saying that he knows the gas tube is the single most important part on the M4; so how often should he clean it. That got my mind into thinking about the mechanics and I realized back then what the op is saying.
I would just make sure the gas block is removed or something is in the gas tube hole of the gas block so fire does not come back towards the shooters face.
Lastly I came to my own conclusion that the gas tube is certainly NOT the single most important part. You need a barrel before anything else. Think about it, you could jam a round into a bare barrel and set it off with a hammer and a nail. Shoot, just rock and a nail.
Just be prepared to eat that rock and nail.
lol yeah with nothing behind the round the bullet might not go anywhere, if there's space for enough pressure to exit the breech. After all, if a loose round gets cooked off by fire or whatever, the bullet doesn't really move because it's far too heavy compared to everything else and pressure takes the path of least resistance
Actually, no.
With the lightweight M16 or M4 barrel (~3/4 to 5/8" diam under the handguards) the barrel will rupture before the gas tube in sustained full automatic fire. It takes around 3 minutes/500 to 600 rounds.
This was not by design was it?
What about the current M4 profile barrels?
Do you mean the heavy SOCOM?
https://cdn11.bigcommerce.com/s-k5jq3j85wp/images/stencil/640w/products/720/759/colt-barrels-std-no-muzzle-device-nfa-item-colt-14-5-socom-barrel-w-fsb-1812266025001__52769.1580090404.jpg?c=2
That profile was designed to increase the full automatic endurance, it turned out that this size over-heats the gas tube first. It wasn't intentional.
[Barrel failure first] was not by design was it?
No, they just made a barrel that was lightweight. No one really cared back then if the barrel ruptured after 600 rounds of full automatic fire, because they figured no soldier carried 600 rounds and would shoot them all in one go.
Do you mean the heavy SOCOM?
https://cdn11.bigcommerce.com/s-k5jq3j85wp/images/stencil/640w/products/720/759/colt-barrels-std-no-muzzle-device-nfa-item-colt-14-5-socom-barrel-w-fsb-1812266025001__52769.1580090404.jpg?c=2
That profile was designed to increase the full automatic endurance, it turned out that this size over-heats the gas tube first. It wasn't intentional.
No, they just made a barrel that was lightweight. No one really cared back then if the barrel ruptured after 600 rounds of full automatic fire, because they figured no soldier carried 600 rounds and would shoot them all in one go.
Thanks for the clarification.
Yeah, shooters who use AGB's know all too well what happens when the gas is shut off (or very close to being).
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