" Stiffi " Barrels every time for every gun for any mode of play. = Light !!!
but if your looking to keep your gun Heavy ? then use any barrel thats out there,
best option is a Unitech barrel from Warped ( top of this page )
Freak - for an actual cocker I like the fact that seriously small bores are available, on other markers the option of small barrels is nice but on a cocker its needed to avoid roll outs with some paint.
I don't have a auto cocker admittedly but unitech (use on my vanguard creed) or freak I swear by I prefer a 1 peice barrel just personal preference and 16" I normally use but its you prefer a lower profile go 14" to keep yourself closer into your cover like I said personal preference doesn't matter too much about your metal as long as it it light and durable then you will be on your way
Stay frosty
The evil pipes kit I had was really good, really accurate. The one downside it had is the same reason I'm looking for a new barrel kit - the tip is very thin and very fragile. I dived (dove?) for cover behind a bunker and caught the ground with it - not hard, no hard at all but it was still enough to noticeably flatten it :-(