M14 Gas Cylinder Q&A

by
posted on July 21, 2010
** When you buy products through the links on our site, we may earn a commission that supports NRA's mission to protect, preserve and defend the Second Amendment. **
2010721153712-m14gas_f.jpg

The gas cylinder on the M14 rifle, and also that on the M60 machine gun, look longer than the usual type. Do these guns use the same gas cylinder design? If so, how does it work? –F.C.E.

Answer: The gas cylinder design is essentially the same for the M14 rifle and the M60 machine gun, though dimensions are somewhat different.

The usual gas cylinder is operated by gas admitted when the bullet clears a gas port in the barrel. The gas at high pressure thus is admitted very suddenly, and its effect is that of a blow on the piston. This is not the most desirable way to put mechanical parts into motion, though it is effective and in fact it is the system used in most current gas-operated guns, generally quite successfully.

The M14 and M60 gas cylinders are distinctive in being designed to deliver a prolonged push instead of a simple blow. This prolonged push is accomplished by admitting the gas into a chamber of considerable volume, where it is allowed to expand and push the piston back.

Functioning of the M14 gas cylinder is shown schematically in the illustration. Gas from the barrel enters the floating piston through a hole in line with the barrel gas port, and fills the space within the piston and gas cylinder plug. The first movement of the piston takes the hole out of alignment with the gas port and cuts off admission of gas. The considerable volume of trapped gas expands smoothly and pushes the piston and operating rod to the rear. By the time the piston clears the exhaust port at bottom of the cylinder, the work of the gas has been done.

In this construction the dwell time (time between firing and beginning of movement of the mechanism) is about doubled. The velocity of the slide when it begins to unlock the bolt is only about half what it would be otherwise. Then the expanding gas continues to accelerate the parts, so that the over-all time cycle is substantially the same as from the impulse of a plain gas cylinder. The low mechanical stresses and bearing pressures obtained with this comparatively slow and smooth acceleration are quite desirable, and contribute to the great endurance of the M14 rifle.

The gas system of the Winchester Model 100 semi-automatic sporting rifle is similar to that of the M14 rifle. This was pointed out by Winchester when the Model 100 was announced in 1960.—E.H. Harrison

Latest

Gotw Wilson Combat Divison 77 Project 1 Web
Gotw Wilson Combat Divison 77 Project 1 Web

Gun Of The Week: Wilson Combat Division 77 Project 1

Join American Rifleman staff on the range in this video to get a closer look at Wilson Combat’s somewhat cryptically named “Division 77 Project 1.” 

The Armed Citizen® July 18, 2025

Read today's "The Armed Citizen" entry for real stories of law-abiding citizens, past and present, who used their firearms to save lives.

Review: POF-USA LMR BASE Rifle

The Patriot Ordnance Factory LMR Base offers a .308 Win. chambering in a lightweight, AR-15-size package, which makes it a capable platform for today's new gun owner. And it comes at a fair price.

2025 Accessory Of The Year: Wyoming Sight Drifter

For each of the past 23 years, the editors of American Rifleman have convened to select our top picks for the past year’s best and most innovative products. Here are the most recent winners.

Henry Donates Rifles To Support Young Leukemia Victim

Henry Repeating Arms has donated a limited run of 50 “Team Keane” Golden Boy .22 lever-action rifles to support 13-year-old Keane Rhodes of Universal City, Texas, who is currently undergoing aggressive treatment for ALL T-cell leukemia.

Rifleman Review: Springfield Armory Echelon

Springfield Armory introduced its Echelon in 2023, bringing a modernized, chassis-style, striker-fired handgun to the market that has since seen several notable line extensions.

Interests



Get the best of American Rifleman delivered to your inbox.