The TM MP7 with a Bingo Airsoft Designs (BAD) kit in it runs rings around every other airsoft MP7 ever made, we all know that. However at an original ~230fps, the standard hopup chamber was never designed to hop much over a 0.25g BB. What happens is the arm is only getting pulled down by the adjuster on one side, and that both limits the hop power you can apply to the BB, and also makes it hook a little. In my case I also found that it wouldn't hold the extreme hop setting well, backing off after a mag or so.
This mod sorts that out completely. You can set your hop and forget it, it'll hop a 0.3g BB to the moon with no trouble at all, and the hop arm is pushed down in the middle so no more hooking.
- An 8x8 M5 gutter bolt nut to slide into the groove
- An M5 bolt to do the pushing (file the end nice and flat). A mushroom head is the best as they have the smallest OD, and use the smallest size allen key of the M5 bolt range.
- A optional spring to apply tension so it never adjusts itself. You can use an M4 mag catch spring cut to an appropriate length
I drilled a 5mm hole through the rail behind the faux screw to allow access with an allen key, but you could just set it and forget it.
The ring on the end slips over the front of the Jack unit in the BAD kit, and these ensures perfect alignment always.
The pictured prototype doesn't have the retaining groove on the right hand side as per the model. That keeps the too fairly snugly together. I did design it to be a snug fit at the front helped with a little super glue, but in practice it's fine to leave it as is, which leaves this mod fully reversible.
2018/04/02 - Added 'no holes' version for user Rokinz