Yes, while searching on-line for the dangerous goods leaflet, I found a petition and stack of letters from folk strongly opposed to RM proposals regarding airguns.

PF48 is an option but the compensation is pathetic. For this reason a very experienced bbs member sent me a pistol by RMSD in the firm belief that it was legitimate.

The sticky regarding posting guns does at times waver regarding RMSD, but the first post still says it is a legitimate means of transporting small low power airguns/pistols? The letter to the OP cited the empty CO2 canister as prohibited, not the pistol. The fact that they disposed of both does indeed suggest a lack of consideration for the sender.

If anyone has written confirmation that RMSD will not deliver a small low power airgun, I would like to see it, indeed it would be best placed in the sticky regarding posting.