Maybe there is an answer to this some place but I can’t for the life of me find it. After looking at many designs of piston AR’s I have a question. Is lengthening the gas key tube so that it never left the gas tube open to put hot gas and fouling into the bolt carrier possible without causing an overpressure situation? From what I can gather you could put a hole some place along the gas tube to let pressure off, like with a piston? Maybe I’m an idiot but this seems like a much more simple way to take much fouling out the reciever than adding springs, rods, and pistons. If I’m totally off-base then please correct me, but this seems like a much cheaper and simpler fix, As always thanks for the feedback guys!
it would be possible but the gas key would need to be incredibly long, it would require a redisgn of the upper gas tube hole, and the barrel nut.
I have often thought about this as well, but im just not convinced the amount of fowling from the gas key is worth it.
It would just be drilling the hole a little bigger right? And getting the gas key tube lengthened? Now I’m really thinking about this. I have an extra upper, I am tempted to try this. It would still be cheaper by far than a piston system too. Has anyone done this before?
What’s the point? A “cleaner” gun? It’ll still need lube…it’ll still not need to be cleaned constantly.
All you be doing is spending a lot of money on something that 1) won’t net you any real benefits and 2) will likely cause malfunctions at some point in time.
At the end of the day, all this fouling and carbon and general “dirtiness” that people talk about with mil spec ARs is really a non issue. It DOESN’T hurt anything…it DOESN’T cause malfunctions…
Changing the length of the gas key will change how much gas goes into the BCG. If it were made longer, more gas will be used and it will take longer for the rifle to vent overboard the excess. Eugene Stoner designed the AR gas system to be self regulating.
How much fouling really gets into the receivers? Does it really cause problems with functioning? My AR has close to 2500 rounds (not counting nearly 500 rounds of 22 LR) with little cleaning other than running a bore snake through the barrel every once in awhile, a quick wipe down of the BCG and the application of lube
Can be done, google ZM Weapons. I’ve got no experience with the system:
http://firearmsandtraining.blogspot.com/2009/01/z-m-weapons-lr300-take-down-details.html
Amazing, I always thought that was a piston gun, very cool.
Awesome, I love it every time I find out I’m not crazy!
The excess gas is vented out through the ejection port at about 1/4" of bolt carrier travel as the gas rings open the exhaust ports.
Extending the gas key really would not accomplish much at all or change how dirty a receiver gets.
That’s very true, but until the gas key separates from the gas tube, gas is still flowing into the BCG
But not under significant pressure or volume.
And dont forget this about piston vs DI One of my favorite threads. https://www.m4carbine.net/showthread.php?t=99050&highlight=Primary+Weapon+System+Bolt+Carrier
I don’t want anything to do with a piston in an AR. I love my DI guns. They cycle softly, and are just plain better at follow up shots. You also don’t have to worry about wrecking your buffer tube or lower receiver. I was just bored and had an extra upper laying around. I was just looking for possibilities or feasibility of this kind of set up. I’m not looking to get rid of my buffer tube either. I have no need for a side folding stock, so I dont need a spring system under the handguards. I’m looking at it from a simple conversion point. Slightly increased diameter hole in upper receiver and barrel nut. I would feel confident that neither of those would pose a problem with reliabilty.
After typing in a few different key words all day on this subject I finally found this
http://tacticalcourses.com/archive/topic.html?b=3&f=123&t=562748
Apparently a longer gas key tube looks to be part of Stoner’s original design? The second picture down looks to be the prototype bakelite type hanguard with the BCG and the longer gas key tube . The only problem seems to be gas pressure relief? Knowing where and how big the holes need to be is the challenge. Finding out that the original design gas key tube was longer gives me a little optimism.