I wouldn't say the hammer drop on the USP is silent by any means. It is just like the P30 decocker in that once it is engaged the hammer is slammed forward safely. This is in contrast to the Mark 23 as well as the Sig Sauer decocker which give you control over how the hammer is dropped utilizing a lever. While this still wouldn't be considered silent it is definitely quieter than the USP decocker. As far as why the hammer is rubber coated on the USP, I think it was an extra layer of safety in case the pistol is dropped. The hammer is also much grippier with rubber coating as well.