Send them to me, I will act as a middle man. You can both buy your guns back when I list them after running them into the ground at a skirmish
There is a (some say pretty decent, but it also has a shitty reputation) website for this for rare trainers, streetwear bits and designer stuff (bags, watches etc) they act as a middle man but also authenticate items to stop dodgy dealings. For the most part it works well, I know it makes a shit load of money. Shame airsoft is not big enough in the UK for this to be a good enough model and for me to make some money from it!!
I would never be the one to suggest a trade. If however someone suggested a trade to me and they had something of interest, I would get them to send theirs first.