Gas Piston vs DI?

[thrillhouse700]

I have read a few threads on this, and somewhat understand how they work. My question is how can you look at an upper and see if it is gas piston or DI?

[NewbieDave]

If you can look under the handguard... see if it's a gas-tube or piston. If you can't, rack the bolt back and see if it has a gas-key or not... that's a great sign it's either gas or piston.

[Josh3239]

Some systems cannot fit under a handguard so you can see the "piston block assembly" sticking out, others have proprietary handguards.

[thrillhouse700]

Ahhhh ok cool so if it has the gas tube (skinny metal tube) then its DI...... Sounds good thanks guys you rock.

[bomb_on_bus]

most gas piston setups have some sort of adjustable gas block that looks more obvious then when compaired to a regular direct impingment gas block.