Bummer..
Looks like I won't be able to post on the CQB on the 12".
Fitted w/ the conventional foregrip, the forestock will require some mods to cycle the action. With the ERGO Pict rail forestock, cycling does't appear to be an issue.
For those looking to swap out forestocks, or mod your 14" CQB to your new Grizz... a couple of quick observations:
1) The Grizz fore end tube assembly (item 28 on the 870 parts diagram) seems to be a couple thou oversize; my ERGO Pict forestock fits, no prob, but I've got to shave some poly off the inside of the FAB forestock for fitting.
I don't have the micrometer readings, as I wasn't smart enough to take them in the front end, and pulling apart the forestocks are a royal PITA...if anyone wants the measurements, I'll strip them down (again...) Sunday.
Your 'as issued' Grizz forestock will bind on the CQB barrel clamp, as it has to ride above your fore end tube assembly.
2) The CQB Buttstock adaptor crowds the saftey, big time. I didn't notice it until today, but it looks like this can be solved with either a 'stock sling plate adapter' mounted between the CQB and the end of the reciever (as long as the loops ride 'high'...), or filing a bit of the 'hook' off the CQB @ the interface.
Haven't shot her yet, as the pistol grip was sacrificed to the Norc CQ311 that arrived first, and was screaming for a furniture change...
Hopefully after I can get the 'back end' sorted out...
I know

, but the ones I have are pretty basic.