Project gun, advice needed

Alright, I'll do some thinking out loud and you can tell me where I'm screwing up.

I've got an itch to build something shorter, easier to wield, and keep out of the way while doing custom hay and seed cutting this summer. Basically a pistol but still legally a rifle, 16" Min. barrel length, 26" min OAL.

I plan on doing the machine work myself to save money. So everything is pretty much factory take off stuff so if I Screw up, I'm not out much.

1) I'm planning to use a Stevens 200 Action, because that's what I have.

2) The only rear grip stocks I can find are the Coopers and I'm not sure if they are still offered or the price and who still sells them or even if it works for Long Action.... I think our local 358Hammer makes them.... Therefore I'm thinking I can get a stock like the Boyd's Tacticool and cut off the buttstock and maybe re-mold the grip area with bondo.

3) I have an extra 270 barrel that I have no plans for... I was thinking of rechambering it to 270 SAVAGE to keep recoil down... If it works I'll change stocks and my nephew(9) can use it for deer season this year.

Here's the problem. I'm figuring I need to face .492 off the existing chamber so figure .500
I have .225 extra thread length.
I can machine down an extra factory recoil lug to make it flat. thickness at .125 orginally .1875
I can lose .300 of the Barrel nuts threaded length, it looks to be .550 now.

If anybody sees a problem with recoil lug thickness or thread length on the nut, I'ld like to know before I start grinding stuff.

And for the barrel:
I plan to cut to the factory barrel to 16.250" and give it a 11* Dish Crown
The chamber is something I could use advise on.
I plan to use a Live Pilot 22-250 Reamer with the pilot for .277 bore
Then, I will have to use a .277 throater...
The part I'm not getting is reaming the neck... Can I just mic the diameter of a dummy round and add .006 and use a chucking reamer or is there a specific diameter over neck size it needs to be to prevent pressure spikes and clean release of the bullet.

Other minor stuff like working over the trigger, feed lips, and larger bolt handle.

I'll need a pistol scope if anyone has recommendations for a decent 6x or 8x.

Usually when I have a smith build something I buy custom dies.... But in the spirit of keeping it cheap.
I thought to buy a Redding collet die and changing out the internals for sizing, Thinking I will have to turn the relief in the top bigger for the neck, and just use a 270 for seating.

Standard 22-250 go-gauge should work.

I'm thinking 22-250 brass may be the way to go instead of 250 savage... better brass options but i've never necked up or down that much...053 Not sure if the brass will take it. Although I believe they used to make 7STW from 8mm Mauser .039

I haven't bought the reamer yet.. But it will be purchased for a future 22-250 or 22-250AI build. Depends on what I need to do this project.

The reasoning behind the 22-250 is powder efficiency in a short barrel... but going AI is basically a 243 anyways.

I'm sure I"m forgeting some info....FIRE AWAY.

Thanks LBass

PS. The chambering might have to Change to a Live piloted 22-243 reamer (future build will change at that point) and same basic plan with neck and throat, dies, gauges, and brass