lay great piles of sandbags, black red green, striped, blue dazzling our eyes.
OK, but I'm just kind of puzzled by these chromatic German sandbags, if that is what he is talking about and referring to(?).
Amazingly, in an Osprey book I own, they have a few paragraphs about the man you mentioned.
Major Hesketh Vernon Hesketh-Pritchard was a big game hunter and former Hampshire County cricketer who was first turned down by the army because of his age, but eventually made it to the front as a war correspondent escort in 1915 (he could have been there earlier doing something else).
It says he actually used scoped sporting rifles, and said to other soldiers "to shoot but not be shot."
It mentions the loophole plates and said he'd fire at them with elephant guns.
He became a sniping officer to the 4th Division, and came up with the idea to set up sniping schools and lobbied the British Army, which did establish them.
I think in your quote (my book doesn't contain your quote) he's (since he was a sniper) probably talking about these metal loophole plates; I don't think they're ammo boxes.
I recommend my book to anyone who's interested in WWI. It doesn't focus on the history of the war per se, but more on the nature of the armies, equipment, weapons, and training provided (or lack there of) for the Germans, French, British, and American soldiers:
Dr. Gary Sheffield,
War On The Western Front: In The Trenches Of World War I, Osprey Publishing Ltd., 2007 U.S: $24.95 / CAN $32.00
This is an actual hardbound book, not a booklet which many of the Osprey titles are; it is essentially a "best of" their WWI titles, and thus will save you a lot of money than if you had to pay for them individually.
I think in one of the RO Maps, "JD10," contains metal plates with loopholes, but no shutters. I'll pass your idea on to the Iron Europe modellers.