Blowback System Vs Gas System

[peck1234]

Just wondering, what are the disadvantages and advantages of blowback and gas feed machine guns/semi-autos....

Reliability issues?

Feeding?

Speed?

Has blowback been fazed out do to the fact that it is pretty much intended for automatic fire?

 

[fun2none]

Reliability, feed, speed are based on characteristics such as inherent design, manufacturing quality, ammunition, and maintenance. They are not necessarily dependent on whether firearm is a blow back or gas operated system.

Blow back is not necessarily designed for full auto only. There several machine guns, like the M2, M1919, MG42, MG3, that use recoil operated mechanisms, which are technically not blow back operated. Heckler and Koch has produced both full and semi-auto guns that use delayed blow back (HK91, G3, MG21, MP5).

In general, gas operated weapons (AR15,AK,FAL,M14) that use center fire cartridges have the following advantages:

• less weight weight compared to delayed blow back
• heat and power fouling are isolated from breech (it's debatable with AR15/M16 )
• gas system can be adjusted for different loads

Delayed blow-back weapons (FAMAS, G3/HK91, Sig PE57/510) usually

• weigh more compared to gas-operated guns
• require more intricate machining operations to manufacture
• may have a small edge in accuracy and reliability compared to gas operation

There are more gas operated weapons in service because they are lighter and easier to manufacture compared delayed weapons that use delayed blow back.

 

[Funderb]

I could imagine that it would be harder to create a light blowback delay mechanism that retained as much energy as a gas block system.
Pure blowback, that you may be thinking of, would eliminate the usefulness of most rifle cartridges.

 

[Jim Watson]

The mass of a blowback's breechblock is proportional to the power of the cartridge. You can't make it up with heavy springs very well. So blowbacks are normally limited to medium light pistol cartridges (9mm Makarov, say) and to medium heavy pistol cartridges in submachine guns (9mm P or .45 ACP). There are exceptions, I know about the big Astra 9mm P and 9mm Largo pistols, and the 20mm Oerlikon gun is an interesting variant, known as "spring operated" by generations of swabbies.

Delayed blowbacks have been pretty well developed and you can have an automatic rifle or machine gun without much trouble. The H&K roller lock is the most common these days but the USA looked hard at the Thompson and Pedersen rifles in the 1920s before going with the gas operated Garand.

Gas operation is more common, though. Most of the recoil operated infantry weapons have fallen out of use, with one big exception in the .50 Browning. And the recoil operated Browning shotguns still have a loyal following; even though out of production, there are enough of the two million built left around to knock down a lot of geese.

 

[peck1234]

Hmm... Thanks guys...

But when comparing the 2 designs blowback does look a lot simpler than gas...

Here 2 links...


http://science.howstuffworks.com/machine-gun6.htm

http://science.howstuffworks.com/machine-gun7.htm

 

[MCMXI]

Those two animations show open bolt systems ... right? They run cooler with less chance of a round "cooking" off in the chamber. Not a problem for most folks but could be a problem for some in harms way. The majority of ARs around have a closed bolt direct gas impingement system. Closed bolt gas piston systems such as those offered by POF are becoming popular too .. in fact, I just paid for one this afternoon.