I have a M3000 and the Nordic Components +8 tube. After opening the loading port (with only two idiot marks) I put it back together and was practicing loading and found it won't feed the first shell from the magazine. Went until 8 shells remained.
I don't think the disassembly and reassembly...
I learned this the hard way on Sunday. I'm a new USPSA shooter and we had a super classifier. First stage was Triple Choice, a tough draw for the first stage of the day. I went way too fast and had 5 mikes and a zero stage. Shot well on the other four stages.