If you decide on a Geiselle SD.

https://www.brownells.com/firearms/...e-16-5-56-nitride-barrel-prod141633.aspx

Use the coupon code and save $80.00 and free shipping (Luna black listed for $1,599.99 before the discount).

Me personally, I'd be looking for a SOLGW.

For starters:

https://www.bigtexordnance.com/product/solgw-m4-exo2-m-lok-rifle-16-black-sons-of-liberty-gunworks/

Watch their videos on YouTube.