Downgrading My MP5

As you dudes know, my MP5 shoots pretty hot - 420fps, consistently, in fact. This keeps me from getting the normal TASO 20ft. engagement distance and could be a problem at large ops. I want to downgrade my AEG while also upgrading it, if that makes sense. My plan was to have the M120 spring and stock barrel taken out of my rifle, and replace them with an M105 spring and a tightbore barrel, 6.03mm or so. What do you guys think? And in case you're wondering, Yes, I know where I can find an M105 spring.

Sounds like a good idea, but your fps will be weak. A stock CA comes with a M110. Just to give a comparison.
-Wyat

I was worried about breaching 400 with the M110. My gun is weird - I get 400fps from the spring, and an extra 20 from what I would guess is compression. M110 = 350, TB = 380, minimum, and compression = 400+. I figured the 105 would be perfect, but I'm not a gearbox expert.

I believe I'll have to take you up on that, RC. I plan on doing some tightbore shopping today, if I have time.

Yeah, the stock CA spring is I believe an M110, which should be good. I hate to sound like a noob, but you say that the compression is a considerable factor in your high fps, but won't that compression be lost when you install the new spring? Just my thoughts. Oh, and you may want to get a good hop up bucking. It will increase fps by about 10, and could give you about 15' more accuracy.
-Wyat

I need to save up about a hundred bucks and take my rifle to The Army Store. Hint hint, WYAT!