Are cylinder dimensions all standardized?
 

I bought the Guarder cylinder tune-up kit for my Umarex G36 but didn't realize that it was ported, whereas the stock one is unported. I like the Guarder one because it's chrome plated.

Suppose I buy another Guarder cylinder but for another gun which is unported, will it work? I measured the dimensions of both my cylinders and they are identical despite difference in porting.

The whole market is standardized to tokyo marui specs, except for a few companies that use some proprietary parts.
Beware that guarder makes both bore up and non-bore up cylinders. The bore up cylinders won't work with regular piston heads.
Match your cylinder port to your barrel length for best results.

So, for a long barrel, I suppose it's better an unported cylinder?

yes.

So, does that mean a cylinder that works for a Marui M16 will work in a Marui G36C?

I made sure I got the tune-up kit and not the bore-up kit. The frustrating part is that the product description doesn't say what type of porting it has.

Take a read of MadMax's writeup on why cylinder porting should be matched to barrel length. Ref. Homer Simpson...they are in fact "Speed Holes"

You don't have to match things exactly...but things work properly/better if you do.

The long and short (har har) of it is....shorter barrels will be best served by cylinders with their ports located quite a bit forward. Longer barrels will have their ports further back, or will not have ports at all. Inbetween is inbetween.

There are lots of different naming conventions for the locations of ports...Type 1...3/4..etc.. Google it...there's write ups out there.

Beware of shiny things...a rough/uneven/bumpy surface that is nickle plated is simply a shiny rough/uneven/bumpy surface.

External dimensions...the vast majority of cylinders are all the same size. Due to manufacturing differences they may be a little shorter...but not where it matters.

Exact port shape/location will differ as well between manufacturers...while there is an "exact" science to it, it's not always adhered to.

Some manufactures "assume" that their kits are going into standard setups. An M16 kit is going into an M16 and so it's going to have a non-ported cylinder. An M4 kits is going into an M4 so it's going to have a 3/4 ported cylinder (which is also Type 1 IRRC).

I know that may not answer some of your specific questions...but the base of the info is here, and references to other info is as well.

Okay, thanks for everyone's input. I guess I'll have to bite the bullet and buy one and try. I'll let everyone know how it goes for future reference.

I've done some research before buying this kit. I'm upgrading it to a 400 mm barrel, and by my calculations, I will achieve better efficiency with an unported cylinder. With the ported one, I would be getting around a 1.4 ratio, which is a bit lower than my target of 1.5-2.0.

My measurements were quite rough to begin with, however, so I'll make sure I got my numbers right before buying. Thanks again.

Why don't you get one with the notches cut on the end?

Sorry, I'm not following you -- I'm quite new. What notches?

I think he's referring to one like this.

Not all companies make one with this type of porting, but there is choice in the market. I specifically linked the KA one since the majority of their stuff is decent.

How do these work? I've heard of the tapered cylinders but this is new to me. Who makes the tapered ones btw?