Will the Law folding stock adapter work with a Kaw valley 9mm bcg? Most 9mm bcg's are 2 piece while the law tactical requires a bcg with the removable center weight which is replaced with the law tactical extension. I know there's a few like the angstad arms and qc10. The law valley bcg seems very similar in construction and a good bit cheaper. Anybody know if they will work together?

This doesn't answer your question, but the spinta BCG works, you just pop the pin, remove the weight and cut part of it off. They are also pretty reasonable priced.

I've run a Law Folder with both a CMMG and QC10 bolt, both of which look similar to the KAW unit.  Just like HK_DUDE said, knock out the roll pin and insert the extension.  I didn't need to shorten anything, both bolts only weigh about an ounce and a half less after you replace the bolt weight with the extension.  Both the CMMG and QC10 bolts are 6 5/8" long.  If your KAW bolt is the same length you should be good to go.

Pete