Quote Originally Posted by gatordev View Post
Can someone educate me on the technical side for that LWRC gun... He mentions it's a delayed blowback and says it therefore needs a piston (I'm assuming a Neilson device), but the MP5 and the UMP (I think?) don't need a piston and can direct attach. Are the HK guns a different type of blowback system? Is that the difference?
Interesting. I found this quote:

Helping that threaded muzzle be more effective when suppressed and greatly cutting down on felt recoil as compared to a straight blowback system is a unique delayed blowback mechanism. The barrel and bolt travel rearwards together for a short distance before unlocking, which delays the opening of the action and allows the pressure to drop and more of the gas and pressure to exit the muzzle rather than the ejection port.
source: https://www.thetruthaboutguns.com/ne...br-and-pistol/