Do not buy a 6.05.
What length are you looking for?
PDI you can order custom length barrels...but only in 6.01 or 6.05... 6.01 will work perfectly if you are using quality bb's and only really looking for 250 feet.
EDGi is the best of the best, and you have to custom order them through him on facebook. I would suggest a 6.03 if you are looking at 250 feet+.
Also, as thunder and many other people will tell you...changing a barrel and hop is stupidly simple. Just look up the guide online for your rifle and its dead easy. You should change both of them at the same time.
PDI you can look under TM AEG and find your gun:
http://www.x-fire.org/etop/01.html
There is also a custom cutting service you can order if you want, have to look through the site tho...but they sell all pdi parts and even hop up parts.