That sure brings back memories!
When I was a kid, neighborhood guys and I would get together for "BB gun wars" - which pretty much entailed putting on our Dad's or Uncle's combat gear (or war prizes) like helmets and such and going out to the oil fields for "war".
Understand, that in North Orange county, there were old oil fields that covered the landscape, with derricks, pumps, pipes and trenches criss-crossing the landscape, with the occasional abandoned homesteads or ranch houses here and there among the Sycamores and Oaks.
The weapons of choice were, of course, BB guns, but in my case, I had my Dad's hand-me-down Benjamin "pop gun", which was just a lever action air gun that made a considerable "pop" when the trigger was pulled. Being creative, I discovered this "pop gun" was best suited as a trench warfare weapon, because I would cock it, ram the barrel down into the mud/sand then the let fly like a shotgun - often with very gratifying results.
Needless to say, there was plenty of us getting hurt (not seriously and one ever lost an eye, thank God) and I shudder to think what some of those German and Japanese helmets and tunics would be worth today...