I'm no expert, but i would think the new adult size 870 has the same size receiver as the youth model. i'm thinking the stock length of pull is the difference. I see no problem with the 24 inch barrel. One guy on this forum took a Knoxx spec ops adjustable recoil reducing stock for 870 _ 12 gauge and using an adapter from Mesa Tactical was able to mount it on a new 870 - 20 gauge. Both items were purchased from cheaper than Dirt, stock was 78 dollars and the adapter 17 dollars. The Mesa stock no. was 93890. So with that adapter i would think you can use any 12 gauge adjustable stock with that adapter on the new 870 remington 20 gauge . As long as the adjustable stock is for a 12 gauge remington. I hope this helps.
