Whoever is claiming breach of an agreement has the burden of proof of establishing their claim by 51% probability.
Transactions involving goods (i.e., AEG's) are subject to the mysterious complexities of the UCC Article 2. Bizzare stuff, but in a nutshell, if the AEG sent was not what was advertised (and thus the subject of the purchase), the buyer can revoke the agreement and recover his money, but he must return the non-conforming AEG as well.
The problem here is they traded one USED good for another USED good and the only remedy is they each return it to the other. Otherwise, market value controls and that aint much.
Threats of civil litigation in order to compel performance in a civil matter are almost never extortion. Almost never because there are very specific instances that dont apply here so I won't discuss them.
However, threats of CRIMINAL action made for the purpose of compelling behavior where the threat maker has a financial or pecuniary interest is almost certainly extortion.
For the record, private citizens do not file criminal charges such as mail fraud. A complaint is made to the responsible law enforcement agency who then investigates for evidence that supports ALL of the elements of a crime. Once the LEO agency is satisfied it sends the case to the prosecuting attorney who then makes a legal evaluation of the case and either charges the defendant in court or declines the prosecution (or sometimes sends it back to the LEO for further work).
On point, an offer to resolve a civil dispute by an exchange of money happens every day - but if the threat of criminal action is involved then it would be unethical for a lawyer to even participate in the case and most likely its a crime - IF the threat of criminal action is so closely connected to the settlement that its clear the only purpose of the threat is to FORCE the settlement.
blah blah blah....
Poisin - take you lumps and learn - it would cost you nothing less than $5,000 to even begin the legal process with a skilled civil litigation firm.
Up State - regardless of your culpability here, in this very small airsoft community the general concept of "where there is smoke there is fire" applies and if you want to change what yo ubelieve to be an aside to your reputation its up to YOU and you alone to be the honorable person here. Otherwise.... STFU and take your lumps like a man.