Best Way to Lower FPS? (Gotta love Ireland)

Stephen-mx3

Right, so I am sitting at about 325fps with my current setup (Systema Silent Head piston, VFC metal gears, Madbull Blue Hopup(old), butchered 6.05mm brass inner barrel). I have just picked up a Tanio Koba Twist Barrel which is about 70mm longer than the wrecked, standard inner barrel and a Systema hop rubber is currently somewhere over the Atlantic Ocean on its way to me.

What I am worried about is that these much needed mods may push me over the joule. So what is the best way to lower my FPS?

Can you modify/purchase a modified air nozzle with small vents? Would short-stroking be the best method?

I eagerly await the responses of the Irish airsofting elite that reside in the cache of the boards.ie servers

Puding

I would expect your gps to actually go down with the twist barrel dye to how that works, could stay the same but it is hard to tell, bit with not go up in fps like a similar length tightbore would

if you do need lower fps on anything I would never recommend drilling/venting a cylinder or nozzle, your just going to create inconsistancy, change the spring

Stephen-mx3

I thought about the spring alright but I am unsure of what spring is in it, could be a 100, 110 or could be a 90!

Will have to put in the parts and chrono it I guess. I had a feeling it would drop alright, but to be honest, with new rubber and a barrel whose end wasn't filed with the roughest round file you can find, it could easily tip it over

Inari

If it's firing 325fps (w/0.20g BB's) in a 6.05mm tight-bore barrel, I would expect it to be firing at 300 or so with the TK Twist, as it has a diameter of closer to 6.1mm. The new hop up rubber could bump up the air seal, but not that much (especially considering how tight a fit those madbull Blue's are).

If your gun ends up a little hot, there are a couple of things you can do. You can:
1.) Change the spring. With the 1 joule limit, if you get your rifle firing right with a good air seal (i.e. no leaks), then realistically your gun shouldn't be pulling more than an M85 spring.

2.) Cut a couple of coils off of current spring. If you're just over, you can snip 1 or 2 coils off of your current spring to bring it down. Just remember to not cut from the closely coiled end (on a non-linear spring). Also, when you cut the spring, file off the sharpened end, and give it a gentle squeeze with a pliers - this will stop the spring from wrapping around the spring guide.

3.) If you're ever so slightly over, what I have heard of some people doing (never have done it myself, so please regard as complete hearsay), is filing the front of the air nozzle so there is a slightly larger gap between it and hop up. This can only be done when it is ever so slightly over, as you're interfering with an integral part of the system.

I really cannot see your gun going over with that barrel and hop combination, so I wouldn't worry too much...but if it does, a new spring (go with an M85 or so) will cost you approx €10, and you'll be far better off