Well an MP5 is a post-sample machine gun, so it is hard for an ordinary dealer to stockpile those. IME, unless you are really big, HK will channel your order to an LE/Distributor, who will take your order and drop ship to the LE/Dept.
On the other hand, there are many MFGs who will sell direct (other than post samples), though many are moving to selling to distributors only unless very large order.
See/touch/learn about products I did not know existed or how they worked. Lots of products look good on paper, but actually seeing quality, etc, they are dogs. I find it much easier to make deals in person than over phone.