From what I've read the JG BAR-10 is a closer clone of the TM G-Spec (read: 303mm inner barrel) whereas the Well MB03 uses a custom length barrel and an unconfirmed threading on the barrel end. This means that if you buy a Laylax/PSS10 barrel you're either too short (430mm) or too long (555mm) or as Skladfin mentioned you can get a custom one. As well it's not confirmed if you can place a silencer on the end of the Well's barrel to cover the inner if you do decide to go longer.
Keep in mind that the TM VSR-10 trigger group was never designed with a 400+ FPS output in mind. The reason the Laylax Zero Trigger and the PDI v-Trigger exist is to get around this problem with a completely different design. With the stock springs in the Well/TSD the sears in the trigger are bound to break at some point. Upgrading the sears (or buying a better trigger) and getting a better piston will cost you almost as much as the gun itself but would increase the reliability of the gun by a huge margin.
Last edited by tsuru; March 3rd, 2008 at 01:00..