I have this gun that's so darn hard to close and open with rounds in the chambers. It's OK to close and open without anything in the chambers or if I use plastic snap caps. It seems that the brass base of the regular rounds has to be squished into the barrels quite a bit for the gun to close. Any ideas about how to make it work a little easier? The gun seems to show very little use, but should be broken in already. And it is not dirty either. Any help appreciated.