Yes, I also think this is normal. I had the same experience with WEM's 20mm Flak Zwilling guns: the brass guns had some flash and were slightly bent. Nothing hard to fix though (you can see the result on my webpage below).
If you really feel unconfortable about sanding off the extra flash and getting the barrels straight again, I would suggest to contact YM and explain the situation. Most of the guys selling PE and brass parts are good-natured and, being modellers themselves, usually willing to offer their help! They could share their experience with you and give you some advice, and perhaps even agree to exchange the set for a new one.
Also, next time you order a brass set, you could try to contact the seller and explain that you need a really clean set - if possible.
This may sound a little naive but I strongly believe that most problems can be solved by friendly and constructive communication.
On the other hand, one could see this as a perfect opportunity to learn new techniques & enhance its modelling skills !