First you just have to decide if you want to fix the stock & go on, or send it back. It is not hard to fix, it all depends on whether you want to do it or not.
To repair it, cut a piece of wood the size & shape of the routed out part, LESS the RR hole part. Nutherwords we are going to put a cap over that hole.
Cut the filler piece it to fit,
Take a 3/8" RR (if that is your hole size) and cut 3 pieces off it 1/4" long.
Lay those pieces in the routered out RR hole one on each end of the routered hole & one in the middle.
Now take some Accraglas Gel & mix it, put some around the edge of the hole, around the edge of the filler piece, slip it in, smear it smooth on the top of the filler sealing all cracks & let it sit 24 hrs. You just patched the hole & strengthened the stock.
Now go to the hardware or Lowes & buy 4' of 5/16" round rod & a 25/64" metal drill bit. .
Braze or weld the rod to the bit keeping it Straight. If it comes out a lil off, heat it red hot & put it straight & let it cool.
Mount the stock in a vice at the Lock area, support the Forestock. I drill them al the time by myself, in fact, I drill out EVERY stock I get, as a 3/8 hole & a 3/8 RR just don't jive well.... you need clearance.....
Lay the drill in the barrel channel. Put on a leather glove & hold the bit down at a smooth area of the bit (upper shank) and start the drill & start drilling, Back out MANY times to clear chips of you will hang the bit !!
Drill out the hole, the 1/4" RR pieces, Accraglass dribbles, etc.
Now you have a hole large enough that a 3/8" RR will go in, you don't have to taper the RR (which I will try my hardest not to do) and the routered hole is capped & the hole is drilled out.
The drill bit will follow the main hole, so it will take care of that offset at the entrypipe, routered out part, strengthen the stock. Just run it back & forth many times to insure it got all the wood & is not binding.
Personally, I will not build one that is routered out this way, as it is additional work to fill & I don't like patching something before I start working on it. However, there are a few stock shapers that cut them like this. Just depends on what YOU want.
Someone mentioned that some precarves come with too much wood taken off the forestocks. That is because newbies want the parts to drop in, sand & finish...... Also IMHO, the vender wants you to shape it like HE wants it shaped. Look at different suppliers & you will find many with plenty of wood left on the forestock. Some leave them totally squared off on the forestock & personally I prefer that. Takes about 20 min to take that wood down to where ya need it, and you have a good solid forestock to work with until the time come to slim it down.
Keith Lisle