Where law enforcement organizations have gotten involved here is writing a "law letter" saying, "Dear ATF: We're interested in firearm X. Please let machinegun

Where law enforcement organizations have gotten involved here is writing a "law letter" saying, "Dear ATF: We're interested in firearm X. Please let machinegun dealer Y acquire a sample to demonstrate it for us." Then dealer Y can buy firearm X and keep it as long as they maintain their license, only being able to sell it to the government or another licensed machinegun dealer.