Increasing Fps in m4

[padraigthesniper]

How would you guys recommend upping the fps of a KA m4 sportline aeg. I changed the spring down from a m120 spring as it was shooting hot now its shooting 290 fps which is too low for my liking. I put in a new hop up and tightbore barrel so its got great groupings and backspin atm but the bb speed is slighty too slow. Should i tape up the hop up unit for air seal more? i want it shooting 330-340.

 

[Asomodai]

How would you guys recommend upping the fps of a KA m4 sportline aeg. I changed the spring down from a m120 spring as it was shooting hot now its shooting 290 fps which is too low for my liking. I put in a new hop up and tightbore barrel so its got great groupings and backspin atm but the bb speed is slighty too slow. Should i tape up the hop up unit for air seal more? i want it shooting 330-340.

Just checking. Are you getting 290 with the hop off completely?

You won't get that big of an increase just taping up the hop unit. What strength spring did you put in it? If an M95 or over you'll need to check your air seal stuff in the gearbox as air is leaking and probably in more then one place. 

 

[padraigthesniper]

it was a m95 i'll check the gearbox for air leaks thats probably whats up.

 

[ak2m4]

yep check compression first, then you can try a M100 spring but every spring manufacturer rates their springs power differently.  Go for a spring which will get you just over the fps / joule limit and then snip and/or heat the coil till you get the desired fps.  

 

[Rogerborg]

You've still got the "M120", right?  Lop a couple of coils off, depending on how hot it was originally - and I mean one, two or three unless you were way over - then heat and flatten the last coil.  Springs aren't complicated, just have a go.