When using a USP Compact and AAC Evolution the slide may hang up as it returns to battery position.
Now even drop in barrels often need a little tweeks by a gunsmith. So when this happened to me the first time I figured it was the barrel needing tweeking. I took the set to my local armorer who has a very good reputation. After test firing a couple of times we were able to duplicate the situation.
While he did trim the barrel for a better fit, to my surprise he said the real problem was the recoil spring. (I think I'm using the correct term) He said with your basic ammo there just wasn't enough pressure to cycle the slide properly. I had two options: 1) Get a different recoil spring or 2) use P+ ammo. The problem with plus ammo is, it's not subsonic so that kinda defeats the purpose of using a silencer.
I searched for a new recoil spring but wasn't able to find one so I started using the Evolution silencer on my 226. NOW, that's not to say the combo won't work on your Evolution/USPCompact combination. But it did not work perfectly with mine.
Finally, I'm sure we're going to hear; it's the barrel, it's the barrel, it's the barrel. But without the silencer, my barrel functions perfectly and is accurate. With high pressure ammo the combination seemed to function fine. That fact, in combination with the word of an experienced good reputation armorer tells me it's the spring.
So there you have it. For the record, I am satisfied with my Evolution Silencer, my EFK barrel, and my USP 9 Compact. The combination just didn't work with the subsonic ammo I want to use with a silencer.