I hate to double post but I spent some time working with it this morning. I think the lack of a gap was caused by a few things. The front of the receiver was quite dirty and the mag tube wasn't fully seated into it. I also found that the forend had shrunk in the back a bit and tilted down, forcing t...

So the mag tube should be flush to the barrel. Good to know. I'll take a look. Thanks for the feedback.

I just picked up a 71 JM Marlin 336 in 30 30. While taking apart for cleaning I realized the front barrel band is super tight. So tight that I had to drive it off with a punch. So much so that it actually pulls the mag tube up to the barrel in the front. I would have to think that this amount of str...