I've owned/own a new and old version CA MP5.
The new one has it's own deal. However, he body appears to still have all the same notches as the the old one. An old hop up LOOKS and only LOOKS, as far as I can tell, like it would fit on there from my memory of the old one.
If you're doing a body swap, doesn't the new hop-up unit come along with the CA B&T body? The new CA ones are a lot better, so why not use it if you can or get it if you don't have it.
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