MP5K, HK53K, and even the HK53. Do you guys remove part of the receiver to put the cocking tube far enough back?

As best as I can tell from pictures the MP5K uses an MP5 cocking tube but set farther back in the receiver.

As best as I can tell the HK53 uses a normal .223 tube but set farther back in the receiver.

As best as I can tell the HK53K uses the same tube as the HK53 and itís placed in the same place as the HK53 but the front of it is chopped off.

I would really appreciate anyone with knowledge in these areas to tell me if Iím under an incorrect impression on any of this.

Thank you!