So digging around YT at 2 am this morning I came across a video by Keystone Carry and he had a reftro fit kit by Superlative Arms with an adjustable gas block....looked pretty interesting, any comments or feedback on this company/retrofit kit?

Bronc

Aero is using their system in the recently released Aero piston uppers.  I guess that's an endorsement of sorts.

I love them.

Been running mine for over a year with no issues. I really dig the minimal carbon buildup, just relube when you're getting dry and it's gtg. FYI, it also pings.

I have a couple of Adams Arms kits, but I ordered a Superlative to try on an 11.5 mid length 5.56 SBR.  I am hoping the Superlative does ok with such a short dwell time.

I have a 4 Superlative Arms kits. One for 14.5" 5.56 with a Adams Arms lightweight carrier and another 14.5" 5.56 for a Adams Arms strike key with an EWS bufferless carrier. I then have a third one for 10.5" 7.62x39 for a EWS bufferless carrier which has a Adams Arms strike key. Lastly, I have one for a 16" 7.62x51 (small frame AR-15 308) POF Rogue that uses a a POF Revolution carrier. They all function perfect.

Best thing about these kits is they work pretty much no matter what you do. All of my above kits are 'different' from stock. For the Adams Arms Carrier, Adams Arms strike key, and POF Revolution (piston) carrier, they all needed filed down piston rods. And long as the rod is filed flat and there is a slight gap between the rod and the carrier when unfired, the rod wont bend and is unlikely to break.

Obviously I've used them in stock configuration and they've worked just fine, but I like bubba'ing my rifles.

I've got both an Adams Arms and and a Superlative and each work fine.  The Superlative took quite a few adjustments to tune per instructions and I have only used it so far with Federal XM193F.  The two biggest advantages for me was the Superlative's light weight for that build and 5/8" gas block; Adams only comes in 3/4".  When I had a question, Superlative's customer support was very helpful.  The updated instructions available on their website was much better than the written ones that came with the kit which was a couple years old when I used it.  Adams was equally helpful addressing an issue and that was approaching a staff person at a NRA Annual Meeting.  Neither brand's kit strike me as particularly robust when compared to factory units on Sig or LWRC but are adequate for my uses.

FWIW I  put Midwest Industries Gen 2 two piece handguard on both (MI-21M) without any clearance issues

I have 4 kits also. Two in 5.56 systems, one is a carbine length 12.5 barrel and the second is a mid 14.5 barrel. The other two are in pistol length .300BLK setups. Never any issues and wouldn't go with any other system!!

One concern with the superlative design is that the rod spring is in a small tube with the hot gas. Under sustained fire, the spring  will burn out and cause a malfunction.

I did ask Superlative and they said their system was tested with thousands of rounds , and the system doesn’t require the spring to function.

I haven’t put mine to test.

I have one I use without the spring

I have one on a 18" 5,56 and had one on a 22" 224 Valkyrie. I sold the 224V barrel, bolt and the piston system to a new owner.
Both are running flawlessly. The SA piston system is the Gold Standard of aftermarket piston kits.

how have you managed to get the .300 with pistol gas to function reliably? What's the barrel length? Suppressed or unsuppressed? Subs or Supers? I ask because i've been trying on and off again for years

otherwise I've had nothing but good experience with superlative kits. Have a few in various length guns (8.0" pistol-18" rifle) and have been able to get them all dialed in, and nice for shooting suppressed

Their piston kits are back in stock as of yesterday.