These pistols are test fired, I've seen some that come from the factory more dirty than others.
You need to put 300 to 500 rounds through it for break in before you should trust your life to a new pistol. Look at it this way, some of the break in has already been done for you.

As Sistema said, your only loss it that you weren't the first person to get it dirty.
I would be more bummed if it came squeaky clean and hadn't been test fired, even more bummed if it had been shipped with a function issue because it hadn't been tested.

Ideally, factories would test fire then clean the pistols before shipping, but then it would be hard to tell if they were doing their job and test firing them.

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U. S. Army Veteran