Why does everyone do their own thing with AR-10?

[cdb1]

The AR is not a direct impingement system, no matter what the internet says. A Ljungman is. The AR gas system is different. Eugene Stoner states in his patent application the gas system is not a direct impingement system. The US Patent Office agrees.

Superheated gasses do not enter the carrier. The gas cools quite a bit at the gas block and as it travels through the gas tube before getting to the carrier. That's how the gas block and the gas tube get hot, from the gas throwing off it's heat which cools it. Yes, there is powder residue, but there is also powder residue that fills the flutes of the HK roller delayed system and those flutes are critical to reliable extraction.

ARs do not require chrome bores and chamberss to run reliably although chrome lining helps in adverse conditions. One place that chrome lining is needed is in the expansion chamber (a feature NOT found in direct impingement system) of the carrier. The HK roller delayed system benefits from chrome lining the chamber for the same reasons

AR's will run long enough without having to be cleaned that I consider them reliable. I also don't buy the need to have chrome barrels and chambers. In fact I PREFER the barrel to be not chrome lined in my AR because I've found them to be more accurate.

I of course reserve the right to change my mind if I find myself in daily firefights expending several thousand rounds without the opportunity to clean my rifle.

 

[MCMXI]

The AR is not a direct impingement system, no matter what the internet says. A Ljungman is. The AR gas system is different. Eugene Stoner states in his patent application the gas system is not a direct impingement system. The US Patent Office agrees.

And yet, in that same patent application ...

" Having thus described my invention, what I claim is:

1. In a gas operated system for a firearm, the combination of: a receiver; a bolt carrier slidable in said receiver; expandable chamber; and means for carrying the explosive gases resulting from the firing of said firearm to said expandable chamber whereby the gases operate within said chamber directly on said bolt and said bolt carrier to retract said bolt carrier relative to said bolt."

So the gases operate directly on said bolt and said bolt carrier ... but it's not a DGI system ... because "operate directly on" isn't the same as "impinge directly on" because the word "impinge" only means to have an effect or impact on or upon, to strike; dash; or collide with. I do get the subtlety of the fact that the expanding gas isn't directly moving the bolt rearward but that really seems like semantics, particularly when compared to a system that uses gas to move a rod to move the bolt. In one system there's gas directly in contact with the bolt and in the other there isn't.

For the record, I own a number of ARs with both systems (blow back too) and don't have an issue with either one, or how they're described. I shoot a lot of suppressed ARs these days, both are noisy compared to bolt guns, both blow gas back in my face, both foul up the magazine and rounds in the magazine, the push rod models somewhat less perhaps, both are accurate, the push rod models require less cleaning, ... what's not to like?

 

[MistWolf]

Your argument is that since the gas acts directly on the bolt (the piston of the AR) and the carrier (the cylinder), that it is a direct impingement system?

Using the same logic, any firearm where the gas acts directly on the piston and the cylinder would be classified as a direct impingement system. That would be almost every gas operated firearm, most particularly, blow back systems

 

[MCMXI]

Your argument is that since the gas acts directly on the bolt (the piston of the AR) and the carrier (the cylinder), that it is a direct impingement system?

I don't have an argument, I'm simply quoting the original patent and everyone is free to interpret the wording of the patent as they wish.

"whereby the gases operate within said chamber directly on said bolt and said bolt carrier"

Using the same logic, any firearm where the gas acts directly on the piston and the cylinder would be classified as a direct impingement system. That would be almost every gas operated firearm, most particularly, blow back systems

For a blow back system, the gas is pushing the cartridge case rearward which is pushing on the bolt or breech face so one could ague that the gas isn't directly pushing on the bolt. The cartridge case is acting as a push rod while the gas is expanding inside the case, chamber and barrel. The cartridge doesn't form a perfect seal but good enough I suppose to prevent excessive erosion of the bolt or breech face.

 

[MistWolf]

I'm just telling you where your interpretation leads because in every type of gas operated firearm I can think of, the gas "directly acts on".

The case in a blow back system does not act as an op rod. It is a piston. It turns pressure into mechanical motion. An op rod transfers mechanical motion

 

[Robert]

The OP seems to be on the right track. This is now generating more heat than light so let's call it a day.