I have one of the NFA modular bolts. It has a solid rear section, so would it be possible to have it machined out to accept the LAW folding adapter?

Sure.
I would weigh it before and after, you made need to increase buffer weight for the material you remove from bolt.


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It's not specifically what you are looking for, but I did some weights myself when I did my build:

QC10 Glock-cut bolt, mass-adding weight (including pin): 3.5oz

Law Tactical folding stock adapter Gen 3-M carrier extension: 2.2oz

I'm using a Blitzkrieg hydraulic buffer and it runs like butter so far.

I actually purchased the NFA modular bolt to use on my qc10 build and then like the next day the law folding adapter went on sale so I had to buy it.  

I had a buddy who was going to machine the modular bolt but I was able to return it to joebob and I bought a spinta bolt instead which has worked really, really well.



edit: did have to remove a weight from the back of the spinta bolt.

Nice pic.  Welcome to ARFCOM.  Got any Legos?