On number 6 I would have to go with the Locking Block.
There is no doubt that the springs on the recoil spring guide does compress when fired. But without the Locking Block there would be nothing to stop the rearward movement of the recoil spring guide assembly and Barrel. So I would have to say the Locking Block. You are correct on your other previous answers.
The Constitution is not an instrument for the Government to restrain the people. It is an instrument for the people to restrain the Government!
“Americans have the right and advantage of being armed. Unlike the people of other countries, whose leaders are afraid to trust them with arms.”
James Madison. Author of the 2nd Amendment