Flasc T9.1 barrel question
So I have an MP7 shroud coming in the mail, and shortly before that I purchased a T9.1 flasc barrel to go along with it, but I have a T8.1. I was thinking that the barrel would be just fine to use in the 8.1, it would just have the extra groove for use with a hopper. What i found out was that the groove to lock the barrel in mag-fed position is not as long as the one for hopper-fed, or the groove on my stock 8.1 barrel for that matter. So basically the barrel sits back a little farther than it should and the bolt hits the back of the barrel with a nice "ping" on every shot.
My question is, was this a manufacturing defect or is it supposed to be like this for the 9.1? And basically, is there anything I can do to fix it without ruining the barrel? Or do I just need to sell it and find an actual 8.1 barrel?
I tried to explain it as best I could, but if you guys need a picture, I could get one up when I get home from work tonight.