AR15- What's a gas block?

[RM]

Could someone explain to me about what a gas block is and does on an AR-15? Is an adjustable gas block better? Are they for A3 configurations only? Thanks for any information.

 

[Swampy]

RM,

The gas block on an AR15 is the cast block of aluminum that goes around the barrel at the gas port. The gas tube comes in the back side and the front sight base is an integral part of the top of it (on an A2 model). On some varmint and space gun types it's more or less just a block of aluminum that sits in the same place and serves the same function, but without the sight base on top.

Sorry, never heard of an "adjustable gas block", unless you are referring to one that is held in place with setscrews instead of being pinned in place. This allows you to adjust the cant of the front sight in relation to the rear....

Best regards,
Swampy

 

[Kharn]

An adjustable gas block wouldnt help a standard rifle cycle any better, since the gas port is already drilled for the correct amount of gas. Now if you were willing to drill out the gas port, the adjustable gas block would be useable to increase or decrease the flow of gas (sort of like an FAL's gas regulator).

Kharn