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This item will not work with those types of lowers. 80% lowers are incomplete lowers that still need final mill work to be a functioning lower receiver.
We have found that many 80%, carbon fiber, and polymer receivers are not within Milspec tolerances. Lower receiver must be within Milspec for our trigger to operate.
This trigger works FINE in a 80 percent lower, it just depends on what jig you use to mill out your lower. Sure, if you use a jig that involves drilling 40 holes start the milling process, and mill it with a drill press or something, it may not fit/work. I used a 5d Tactical jig, which uses a router to mill, and my trigger installed just fine. The sidewalls are even and smooth when done on a 5d Tactical jig, and the pockets are milled out clean. I'd imagine someone who uses a CNC machine to machine out the pockets should be fine to, as long as they input the right material to be removed.
Not saying ANY 80 percent lower will work, just saying it depends on YOU and how/what you use to mill your out. It does need to be milspec, but this isn't impossible to do.
I milled my 80% with a router and measured the dimensions. They were spot mil spec for the trgger housing. I had no issues installing the BFSIII. The key is to measure your dimensions. The width between side walls is what is critical. Too narrow is ok because you can remove material from the BFSIII or the side walls. Too wide is a no go. My dimensions were exactly on spec yet I still had to stone the mouts on both sides by just a hair and now have a perfect fit. I have fired over 600 rnds and had no issues.
The answer by Carly R. makes it evident she does not understand the issue. Of course when someone asks, "Will it fit in an 80 per cent lower?" they mean one that has already been milled out. FA says it doesn't fit 80 per cent lowers as a disclaimer, so they won't have to cover all the inferior jigs and people who do not mill the lower out properly. A properly milled out 80 percent lower can and should be within milspec.
You are correct it may not work in some 80s or polymer lowers. However, i currently have this in a polymer lower and its been flawless so far. So all in all results may vary.
I have milled several 80% Aluminum lowers with the 80% Arms Multi jig and they all worked with the BFSIII AR-C1. Can not speak for the Polymer or Carbon lowers...
I have installed two of these triggers on 80% lowers. They work flawlessly. Several thousand rounds through both and not one misfire.
Per an email response to a query, they say the system only works in a milspec receiver, and cast polymer or home-milled are frequently not to milspec dimensions.
I milled an 80% lower with a 5D router jig and dropped a Franklin Armory BFS3 into it and it did not function on binary mode. When I dropped it into my 100% Smith and Wesson it worked perfectly.