Make sure to get the forearm that fits your barrel contour. I think that there are "heavy" and "tapered" barrels for the Encore, so you might need check this. However, I'm not as familiar with the Encore Rifles, so someone else might chime in here? Make sure first.
You can fire both of your barrels without the forearm, just make sure not to let the hing pin fall out, and make sure it stays seated correctly in the frame.