being used by the army for training
Flags.
They have quite long winded large warning signs at entrance to ranges, and then fly flags when in use.
I drove over little tracks on my motor bike once on some hills in late 1970s. I came eventually to a larger lane going downhill. There was an enormous sign and a pole with a flag. I only could see the rear. So I stopped and got off.
I wasn't amused that the range was obviously unfenced at the hills and I had been driving through it for who knows how long. I didn't hear any gunfire or artillery though.
I was very familiar with UK ranges, having used them (Comrie in Scotland was lovely). But it was my first encounter with an Irish Army range.
When we were small, there was a double hedge at the back of the garden. Behind the first hedge was a little stream with an embankment and second hedge. Raised behind that was the Belfast - Larne railway.
We frequently donned wellys and explored downstream. Upstream it emerged from a small culvert at the boundary with next door.
So of course it went past the rear of everyone's gardens, the hedge was sparse, so we could easily enter any garden, though we only entered one (our friends). First was a tunnel under the railway to a field. The other side of the field was the main road with Trespassers Prosecuted sign at the gate. I think it was about a year before we realised that as we didn't go to the side of the field with the noisy main road. Other kids (via the main road) had made a gang hut by digging up the turf and roofing with junk and turf. We were usually unwelcome.
Usually we ignored that right turn under the railway and went on downstream which turned left into a steep gully, down the side of a garden of people we knew. Their garden was inaccessible due to steep banks. Then we bent over and through the tunnel under our street to our friends' house. He had cut steps in the bank so we could get out, to go down through their garden, field then Orchard to the beach. We never risked going down the stream to the beach as it turned into the next garden and wound through their manicured lawn criss crossed by railway sleeper bridges.
However usually I cycled to the beach as we didn't go through their garden unless we were engaged in play with their kids.
One morning though, my parents were surprised in bed by those two kids screaming that the tent was on fire and we (my brother, sister and I) were going to be burnt. The tent was like a dog, it had gone "woof" when we tried to light a fire in it to "make" breakfast on Sindy's toy cooker. My mum and dad arrived in our back garden to find we were all fine, but no tent any more. The only really other very bad thing was ... I better not say. My sister wouldn't be amused.