Other types of airsoft guns

[Skippy77]

I was playing at Airsoft Plantation on the weekend, and there was this lad you had a similar gun that looked like a polar star type gas gun, however he called it something else as the control for the fps was in the gun itself and not controlled by a regulator on the gas canister. He said the setup was £450 and it was an M4 type rif. To get to the fps control you had to open the gun up by removing the rear pin, it didn't look like a polar star as these look like V2 gear boxes where as looked like less moving parts.

Does any one know what these are called?

 

[Rock-climby-Dave]

almost certainly a Tippmann M4

Little adjustment allen bolt on the inside for adjusting fps.