Subsonic cycling - NEMO Arms .300 Blackout Custom Carbine Buffer Spring

Wanted my 300BLK to cycle subs without a can. Specifically the 220gr Sabre rounds from AAC. This spring worked
Before this spring I tried a bunch of stuff I had and some I borrowed from friends including:

Magazines
Sprinco "yellow" spring
Multiple carbine springs
Various buffer weight / spring combos (from "empty", to h4 and many between)
Low-Mass BCG
Gas block(s) and tubes
Dripping in oil
Drilling out the gas port
Also tried the upper on multiple lowers including ones with low-power hammer springs, drop in triggers, etc.

No combination of the above made it cycle reliably.

Installed the NEMO spring and it cycled with a 2.2oz buffer but the ejection was "weak" so I went with aluminum weights (around 1.5oz total weight of buffer) and it worked great. This is with the now drilled port (.125) and regular mass BCG. NOTE: a regular carbine buffer wouldn't cycle far enough to pick up a round. (Winchester Suppressor and White-Box subs DID work)

I used a pull weight-gauge to compare the force needed to compress vs the Sprinco Yellow (using the charging handle) and the NEMO was slightly lighter. (analog gauge was hard to read while pulling, etc)

This spring is shorter by about 2.5 coils compared to my other carbine springs including the Sprinco Yellow.
I would say, slightly softer and shorter.

Will be testing with full power loads soon to see if it can handle them. And a can will be added down the road.
This was a cheap solution and was a lot of fun tuning this pistol to work with what I had on hand. Sure, I could have bought different ammo, but I stock this stuff for another build since it's what it shoots best. I wanted it to at least run on it.