Azrel Sutcliffe livestreamed a Tokyo Marui MP7A1 project last month and you can watch a recorded version if you missed it... "Live stream of some of my upgrades of the Airsoft Replica Tokyo Marui MP7A1. We fit a replacement PDI Muzzle Base to the front of the replica to allow the longer Maple Leaf Crazy Jet barrel along with a replacement nozzle and recoil spring from Creation:

• 150mm Maple Leaf Crazy Jet GBB Barrel
• 50 Degree Maple Leaf Autobot Bucking
• Creation Enhanced MP7A1 Nozzle
• Creation 150% Recoil Spring and Spring Guide
• PDI MP7A1 Muzzle Base

Due to issues with the Creation Spring guide we did not use it in the end as it was causing the bolt to stick. So we reused the stock Tokyo Marui spring guide.

Some of these items were purchased directly from Japan from various vendors on Amazon.co.jp, Rakuten and others. To purchase from Japan with ease I used Buyee (https://buyee.jp​) a Japanese Proxy Service."