.300 whisper AR pistol build

[JFettig]

Hey, new to the forum but not new to the shooting community.
I'm in the process of building an AR pistol in a caliber thats legal to deer hunt in MN slug season. Originally it was gonna be 6.8spc but I think I like .300 whisper a lot better.
I machined the lower myself from a 0% forging and have a dpms parts kit right now, will likely put a 2 stage trigger in it. I started machining the 6.8 barrel from a .270 rem 700 barrel that I picked up for $10 but don't have a chamber reamer nor the funds to pick one up right now. I also include the price of a new bolt, brass and mags into that price I can't afford directly.

So being that I'm in MN and I can't own silencers, most loads would be supersonic, especially for knocking down deer.

Looking at other short barrels I'm seeing around here, I'm seeing gas ports in pistol location regardless of the length, I'm wondering if thats a subsonic thing or if thats the overall optimal location?
I'm looking to have a 10-12" barrel on this, supersonic loads primarily but want to be able to run subsonic loads.
Cost is also an issue(and machine time, living almost 200 miles from my shop right now). I have some servos I'll be selling to fund the remainder of this project. I'm hoping to come by a barrel or upper, another thing I'm considering is getting a model 1 sales barrel or barreled upper and cut it down, turn the end, crown or thread it.
Gas port: How is the gas port sized for .300 whisper? I'd imagine that placement and size depends a lot on barrel length just as much as it does going between supersonic and subsonic.

Anything else to consider that I haven't mentioned?


Thanks,
Jon