Firing Pin and choke M2 Questions

[Palmer421]

Hello. I just bought a new tactical M2 (my first shotgun) and had a couple of questions.

 

1) My M2 came with I, III, IIII notched chokes. Can someone please define each for a new shotgun owner? Also if I shoot slugs, is there a particular one for that/not for that?

 

2) I took my M2 apart to learn how it works and how it should look before I shoot it and noticed the firing pin needs to be pushed up into the bolt assembly in order to expose itself through the head to strike the shell. Is that normal, or have I assembled something incorrectly? It seems that the pin strikes the shell with it's inertia from the hammer rather a direct impact transfer from the hammer to the pin to the shell.

 

3) Upon further inspection I noticed the bolt head retaining pin doesn't travel all the way to the back of the slot in the bolt as the head slides back and rotates. Is that normal?

 

Sorry for my ignorance and I appreciate any help.

[Palmer421]

I posted the same question in the Benelli forum as well and got a really good response--Thanks Kevin. So no one repeats the effort, the same thread title is in that forum (Sorry, I couldn't post the link because I'm too new).