I know this is a basic question but I always hear that a carbine length gas system timing is off and less reliable than a longer gas system and I never understood this. Can someone please explain to me if this is true and why. Thanks
oh ok, I get it now. So if you use say a 10 inch barrel with a carbine length gas system, would the parts be more likely to wear than a carbine length gas system with a 16 inch barrel?it has a lot to do with the gas system's length versus barrel length. Short gas lengths are for short barrels.
The carbine system was designed for a barrel even shorter than the current 14.5" barrels i.e. 10.5-12" barrels. These barrels allow enough gas to escape from the muzzle, and leaving enough to smoothly cycle the action.
In the 14.5" barrels, more gas is trapped in the barrel by time it begins to cycle. This leads to a very abrupt, harder 'push' into the gas key (since this leads to the extra gas being sucked into the gas tube to be used to work the action), and therefore compresses the buffer spring quicker and more abruptly, as the bolt carrier group flies back with way more gas giving it momentum. And as physics dictates, every action elicits an equal opposing action; the bolt will slam forward faster and this leaves the gun at risk of misfeeding, breaking bolts, added wear, etc. etc.. This is why they generally use H buffers in carbines: to make up for the added push from the extra gasses that go back into the gun instead of escaping out the muzzle. This problem is further exacerbated in the 16" barrels that use carbines.
This is also why midlength and spectre systems are being touted as superior in carbine vets due to the extra length in the gas system being more natural to the 14.5-16" barrels they usually use.
In regards to reliability, these issues are NOT urgent enough that you should feel dissuaded from going the carbine route. We are talking about a LOT of use for these problems of wear to manifest in a carbine system.
The benefits of a mid-length and longer are more practical in nature (longer sight radius, extra room on handguard for support shooting, softer recoil), not so much in reliability. A quality AR is a quality AR.
I thought it was from the chamber to the gas port and now finally realize its from the gas port to the muzzle.
It isn't the amount of the gas that is the issue, it's the pressure
I thought that the carbine system used in the M4 was actually adopted (or, at least adapted) from the CAR-15/XM177 derivatives
The M4 gas system is not the same as the old XM177 or CAR-15/16 gas systems. It is purpose built, when Colt was working on the project they subcontracted the gas system and the buffer spring and buffer assembly analysis used in development