[MadMax]

Exactly what Landmine says.

There are little shoulder features which register against a plastic part which is backed by a spring. The Guarder part doesn't have the shoulder features so the part just follows the reed valve instead of switching from "fire" to "recoil" mode. Essentially the path to the breech is always closed so the bb never sees a significant blast of gas and the gun goes straight to recoil mode.

Because the part can also obscure the nozzle port on the bottom, it can also restrict gas flow into the blowback internals so slide recoil can be affected.

I have no beefs with digi cals. I have a waterproof Mitutoyo myself. I was meaning to say that a pair of calipers isn't enough make you a good engineer. You still have to test things out to see if they actually work. Any hack can measure things up and make a reasonable looking copy of something. Actually appreciating the subtleties of a product and duplicating the INTENT of a product too is an extended effort.

I'm really P/O'ed because Guarder apparently didn't take one of their nozzles and actually stick it into a GBB to see if it really worked properly. I've also had problems with their AEG springs which shoot significantly hotter than their ratings would indicate. Their response is that nothing is wrong although I have provided them with actual chrony results (with their own optical chrony no less) on several AEGs. This is embarassing to me as I retail their products and have to issue replacements or refunds to my customers.

Gaah. Their manufacturing quality is very good, but they really have to get into doing some rigorous product testing. Well manufactured parts still have to be carefully designed to be good products.