Barrels

NakedDex

I'll say nothing as regards CA being a "good brand". All I'll say is don't stress it too much.

Like I said, the barrel will just give you accuracy. A tight bore barrel and a good hop rubber will see you most of the way to an accurised set up.

.22 Lover

CA being a good brand in saying if one part breaks 5 different companies make interchangeable parts

NakedDex

Yeah but that can be said of most of the brands these days. The only ones who still have compatibility issues are Star/Ares, and even then it's only with a select few components.
Particularly with Armalites, the vast product lists available for them cover just about every brand on the market in one swoop.

.22 Lover

That's why i love the M16.But one thing i don't know is it hard to replace the hopup and barrel for instance is it hard to fit a hopup unit I'm only 15 so i don't really have any experience with fitting or replacing any parts apart from maintenance and lubricating the hopup.

Big_G

It's probably one of the easier upgrades to do to an airsoft rifle. There are a good few solid instructional videos on the net. Just search around. Mechbox.com might have one.