Originally Posted by orangello
Yup, I opted for the full buttstock WITH a pistol grip, not quite thumbhole ugly but no beauty queen.
When I first bought my 870 it came with a pistol grip and a 20 inch barrel. After one trip to the range, my ex-FIL's 4 inch model 29 felt like a .22 by comparison. I thought about picking up a thumbhole or PG butt stock, but in the end, I found that a set of youth model 12 gauge furniture worked best for me.
OP, the federal minimums are 18 inches for the barrel, and 26 inches overall. In the case of a side folder, the overall measurement is with the stock at fully extended. If you go for a cut down, measure twice, cut once, and set the length after it is cut at 18.5 to 19 inches. All it takes is a loose end on a mesuring tape to put someone away for a long time.
Note: I am NOT a lawyer. Consult with one who is familiar with local, state, and federal laws before peoceeding with your project, or talk with a compotent gunsmith.