I would just order another set of recoil springs and cut a coil off each one at a time. Base line or not, it doesn't work and you've given it as much gas as you can so now you need to reduce the recoil side, I would not lighten the carrier as it shouldn't be needed and will be an expensive replacement if you ever decide to go back to 223.
The piston bleed ports are there to release the pressure once the piston has moved far enough to unlock the bolt and the momentum of the carrier should provide the energy to complete the cycle. If the gas port has opened up and it's almost working I would just balance the system by softening the recoil side of the equation.
That is exactly how I did it when building my NR 300BO conversion for my ACR. I got lucky and the factory gas block easily flowed enough gas to do the job so it was just a matter of testing then adjusting till it cycled well with my loads.
18.6 inch barrel, carbine length gas system, works perfectly.
The 180 should easily be able to run as 300BO, just need to do a experimenting. I'd actually like to see how my ACR 300BO barrel works in a 180C, from the sounds of it my barrel would make for an undergassed system.
Jiffx, I'll try to remember to measure my gas port, prob doesn't mean anything since the gas systems are not the same other than both being piston operated. Pretty sure it will be smaller than the same barrel that was built for an AR since the ACR gas system is much more efficient than an AR gas system, you have to open up the gas port on an ACR factory barrel to be able to run it in an ACR.
Glad someone is tackling this project, it was going to be my next gun project if I got talked into a 180C.
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