Alright folks, bit of a complex question here. I'm looking at purchasing an MCX in about the next month, and going back and forth between getting the Virtus 9" 300BLK model or the Rattler. Either way, I plan to also purchase a SRD762 and the gun would always be run with the suppressor on with supersonic ammo (Barnes 110gr VOR-TX, to be specific). Here's my question;

I know 9" is about the ideal length for a 300BLK rifle, even with supersonic rounds. But I also know that you get a bit of a velocity boost from shorter barrels when you run them suppressed (I've seen it referred to as "freebore boost" before, if that's correct). Would the shorter barrel on the Rattler + whatever freebore boost is gained from the suppressor result in a significant loss of velocity as compared to the 9" barrel? Meaning, will I lose a significant amount of the supersonic ammo's potential effective range, or will the boost from the suppressor negate the loss of velocity from the shorter barrel?

I intend for this rifle to be a dedicated suppressor host, and am looking at it for a go-to home defense and hunting platform with either a 1-4x or 1-6x LPVO for the optic

Suppressors only gain you about 1% velocity on average, in my experience.

For supers, I would not pick a Rattler unless you truly wanted a PDW.

This chart is based on 110gr TSX projectiles.

Well looks like that question is answered. Much appreciated!

Get the pistol in 556 then get a 16" 300 barrel and cut to suit.
Swap calibers back and forth.

Looks like you got you’re answer.
Figured I post my chrono data for reference.
9” MCX S&B200gr subs 930fps
9” MCX S&B200gr subs suppressed 941fps