DeltaReact

It's an older rifle. we bought it used about 10 years ago. I currently don't have a way to measure it right now but I do have a steel mag which might be useful in determining. Also here's a better look at the upper.

Howdy Y'all, so I have been scouring the internet trying to find info and I finally landed here so I thought id just ask. I just received this rifle from my family, its one of the first rifles we ever purchased and I'm trying to change out the handguard but I know there are two styles of rifle DPMS and Armalite. I'm not quite sure which type I have. I know I'll have to change out the gas block but is there a big difference between adjustable and non-adjustable. I'm taking the gun up with me to Alaska this summer and its gonna take a beating. I'm looking for cheap and durable. recommendations would be helpful.