Sentry, Please forgive me for not getting back sooner with the shotgun forearm information. I have had a busy Spring. In comparing Model 220's in 12, 16, 20, 28, .410, and 9 MM R.F. shot, I found the following information. Again, this is for wood only, the forearm must have the same type attaching metal as originally on the gun. The 12 and 16 will interchange with acceptable clearance when the 12 is on the 16 barrel. The 16 on the 12 barrel appears to be ok, maybe a little tight, but could be opened up. I can't be more specific on this because the attaching metal is different on the two examined. The 12 and the 16 will fit the 20 barrel with the 12 having excessive space and the 16 being a better fit. The 20 forearm is to small for the 16 and 12. The 20 forearm will fit the 28 barrel with some slack. The 28 forearm will not fit the 20 at all and is to large for the .410. The .410 forearm will not fit the 28 barrel at all. The .410 forearm will fit the 9 MM barrel with acceptable slack. As a comparison, I tried the 219 rifle forearm on the 9 MM and it was way to big. The 219 forearm will fit the .410 barrel with acceptable slack but is to small for the 28 barrel. I hope this will help some. While I have gotten some much appreciated data from some readers, I still have insufficient data to unlock the mystery of the code of letters and numbers (or lack of) stamped inside the forearms. Best wishes, Garnett