Quick Q on the ar-15 op system and other DI systems

[axxxel]

Hello,

I've never fired an ar-15 (legal obstructions on this side of the puddle) but I have a great interest in all kinds of firearm designs.

Does the ar-15 have any way of venting off excess gas?

I have a rifle quite similar to the m1a or m14 type rifles. When the gas piston has moved some distance, a hole in the gas chamber is opened, which vents off excess gas. This is not enough moderation to make it function reliably with any kind of ammo (as you might know, you're not supposed to feed your m1a with bullets heavier than 180 gr), but at least it's something. Many gas operated mechanisms have some kind of provision for venting off excess gas, but since the ar-15 has no moving parts near the gas port, I figure there's no way to do this.

Of course, there are plenty of remedies availible to handle over-gassed ar-15.

What about other DI systems? The Ljungman and the MAS 49/56, do they have any vents for excess gas?

Just curious, that's all .

 

[Zerodefect]

When the AR's piston/bolt jumps forward, it vents excess out the side of the bolt carrier and out the ejection port, when it has completed it's travel.

See the vent holes in the BCG dent:






It won't reduce any excess force on the bolt though, just wastes the gas after piston travel is complete.

 

[MachIVshooter]

What about other DI systems? The Ljungman and the MAS 49/56, do they have any vents for excess gas?

First, the AR is not a direct impingement design. It is a unique piston design that eliminates the operating rod.

True DI guns vent leftover gas in the same way an op rod design does, except that true DI uses the bolt carrier itself to act as a piston. When the bolt carrier of a DI gun clears the gas tube, the leftover gasses vent into wherever the exposed end of the tube is.

 

[briansmithwins]

Pretty much every gas operated firearm I can think of has a port to vent excess gas, sometimes well hidden, but it's there.

BSW

 

[MistWolf]

When the carrier moves enough to the rear, the gas key disconnects from the gas tube, cutting flow to the expansion chamber. The carrier also has vents that lets gas escape once the gas rings wipes past them. With the gas key disconnected and the carrier vents open, gas in the expansion chamber vents from both places