Yes, a nut, bolt, and washer will work fine. The pistol grip nut has been a problem for me on 7.62 and 5.45 as it is located just under a rivet and I had to file it down both times. Maybe the .223 is similar to the S12 where it is in the open. Anyway, I found the standard pistol grip screw to be too long and narrow for the SAW grip.
Hope this helps.
The top pic is the nut and washer inside the receiver and the bottom one is a very bright flat head bolt and washer inside the grip.