Mossberg 183D-A help.

[milsurpcop]

I just bought a Mossberg bolt action .410 that’s in very good condition. I’m having a couple problems. 
First, the choke won’t adjust. I’ve used penetrating oil and even used heat a d it won’t budge. I don’t want to crank too hard as to damage it. I’m guessing there’s just enough rust to keep it stuck?
Second, I want to completely disassemble the bolt for cleaning/lube. I can only get the bolt head off but I can’t figure out where to go from there. I’ve searched far and wide over the web/YouTube but can only find disassembly instructions for other models and not the 183D-A. There’s variations in the models but no luck on this one.
If anyone knows how to disassemble the bolt and or know how to loosen the choke…I would appreciate it very much!!! Thanks!!!

https://www.dropbox.com/s/xn0u2rqa9ce1h2v/Photo%20Feb%2022%2C%2012%2033%2015%20PM.jpg?dl=0
https://www.dropbox.com/s/njbfqox4vxl7q1h/Photo%20Feb%2022%2C%2012%2032%2042%20PM.jpg?dl=0
https://www.dropbox.com/s/5k5x6s1y1yembgu/Photo%20Feb%2022%2C%2012%2031%2053%20PM.jpg?dl=0

[Danjal]

If I remember correctly some of those had a set of jam nuts on the striker end of the bolt. That one appears to have a single nut.

Otherwise quite a few needed decocked and there's a pin between the rotating sections of the bolt. You'd need to rotate the cocking piece/striker to get it forward, then remove the pin.

[milsurpcop]

I took it to a gunstore that also does repairs. The choke came right off, I was just being too gentle.😂 We think this was a flush screw that backed out a little and had the head either ground down or worn off by repeated cycling. I rotated the pin but the back is still covered so it can’t be tapped out. Unless it’s pulled out?

https://www.dropbox.com/s/2non53j8yym6pzx/IMG_0021.jpg?dl=0

[Danjal]

I took it to a gunstore that also does repairs. The choke came right off, I was just being too gentle.😂 We think this was a flush screw that backed out a little and had the head either ground down or worn off by repeated cycling. I rotated the pin but the back is still covered so it can’t be tapped out. Unless it’s pulled out?

https://www.dropbox.com/s/2non53j8yym6pzx/IMG_0021.jpg?dl=0

I've helped with a few 1903s like that. They just needed a little more love from a bigger hammer to get the pins unseated.

Here. Basically the only area of the bolt you didn't take a clear photo of.  And a video also.
https://www.youtube.com/watch?v=5fKPbS1LghY