Re: Need Help Identifying a Movie Gun
Yes, there is a gap between the magazine tube (not a consistent term) and the barrel itself. It's only about half an inch or so.
And, never fear on not knowing terminology - anatomy of guns is so varied; some things are consistent, but not everything. At least you are better than Diana Feinstein's "the thing that goes up" method of description.
*chuckle*
That being said, to me - it very well could be a different gun altogether. Just seems like a long-mount variant, but then again as someone stated earlier (pfarland, I believe) there are just soooo many manufacturers. Heck, the entire thing could be hand-built in a studio.