Saw some threads recently about `tinkling` noises in T8 mods.... and have been having the same thing happen to me. Well, I was out for a couple of muntjac the other week, and this was what happened to mine when I fired the second shot of the day ... It made me jump a bit I have to admit. I thought I was reasonably good at keeping my kit well serviced, clean and maintained !!! Have got a Roedale Delta V modular suppresor on now, and I have to say it it fantastic - and so much easier to clean and inspect.
Checking my records for the .243 on which it was fitted, this mod has only had 1743 rounds through it.