[GSK88]

Originally Posted by Mr. G36!

Well, if you mean different lengths of hand guards, they should all fit any G36 model. The barrel assembly should be universal as well, but most extension kits are lazy and simply have a barrel extension that screws onto the end of the barrel, replacing the flash hider, while the gas-tube remains the same length.

If you're asking about whether the hand guards are compatible with the carry handles, they don't actually connect, even though it kinda looks like they do. Any should fit with any.

And if you meant something totally different, sorry, but I missed it, ha ha!

As for zeroing the optical sight, what might work is if you set the rifle down and aim down the emergency sights on top of the handle itself. Pick something a reasonable distance away (by which I mean something not too far away, but not point-blank either) and whatever they line up with, tweak the optical sight's reticule to match. Fire, and make adjustments as necessary. If your shots go way off, there's something wrong with something other than the sight.

Bingo! This is exactly the info I was looking for. So usually barrel extensions screw on like a flash hider?

My idea was to take my CA36C and be able to swap out just the inner barrel, handguard and carry handle to a K eventually but I didn't want to buy a kit and find it doesn't actually fit.
Thanks for the info!