Interesting case. Some very good points have been brought up.
The Bead Blasting should have made no effect on the rifles accuracy as far as the rifles fit to the bedding. I say this because every rifle I build for customers, around 80 to 100 yearly, every one is bedded prior to bead blast finished the metal surfaces. Simply put, it will not make any difference. If the barreled receiver is tighter going into the bedding, its for another reason, not the bead blasting because the blasting will actually remove a minute amount of steel. The blast media actually cuts the surface of the steel which is why it changes appearance. It in no way increases in size unless your smith is using gravel for blast media.
So what will cause the accuracy problem, well, reading over your post I see several issues that MAY cause problems. I will go over each. Something happened and changed from when you broke in your barrel to when you get the rifle back. Lets look over what has changed:
1. Bead blasting. I have said it should not effect fit to the stock and that is true. If the stock is tighter, you need to make sure nothing has changed on the barreled receiver such as the smith pulling the barrel for bead blasting and then reinstalling the barrel and the recoil lug is not indexed the same as before. Other then that, the real issue is if the muzzle crown was blasted. I never, EVER blast the muzzle of my rifles. A burr small enough that you can not even see it will destroy accuracy. Bead blasting the muzzle will be very hard on accuracy. If the bore was not plugged and the blast media actually got inside the bore under pressure, your pretty much screwed without removing that last part of the muzzle and recrowning but I am sure your smith would not do something like that or he has no business being called a smith. That would be a really rookie mistake.
2. Scope base. Make for **** sure that the front receiver screw is not contacting the barrel threads. To do so, loosen all base screws just enough so that the base moves easily then screw the front base screw down until you feel resistance. The rail base should be solid. If there is any movement at all with the base, your front receiver screw is contacting the barrel threads and this can also cause some serious accuracy issues. Sand off some length of the front screw until it bottoms out and does not contact the barrel threads in any way. The NF base is a huge improvement over the other rail, make sure recoil lug on the rail base is contacting the receiver properly also, THis screw situation can occur with 1 or 2 piece bases. This problem ususally shows up if the receiver has been properly accurized because the receiver thread diameter has been increased but it can happen with a standard receiver as well just because of screws that are a bit longer then normal.
3. Wyatts magazine box. If its the internal mag box that used a Rem 700 BDL floorplate, you have to make **** sure that the magazine box is free floating between the receiver and the floorplate. You should be able to open the hinged floorplate and reach inside with a couple fingers and be able to move the internal mag box some both on the front and rear of the mag box. If it will not move easily, its binding between the receiver and floorplate and you are not getting a solid hold on the receiver screws holding the receiver down into the bedding. This can cause SERIOUS accuracy problems. Also, make sure that the feed lips on the mag box are not contacting the bolt, if they are, they need to be shortened.
4. Check to make sure that there is plenty of clearance between the bolt nose and the barrel bolt nose recess in the barrel. If there is any debris in this area that is contacting the bolt nose when close you will again get accuracy problems. Make sure this area is clean and free of any foreign objects. This area should be machined so there is around 15 thou clearance between the bolt nose and barrel so there is not alot of clearance but if it does not have this clearance you will have accuracy problems.
I would be surpised if its not one of these things. A rifle just does not shoot sub 1/2 moa and then turn into a 2 moa rifle without something being obviously wrong. The trick is to find the problem and correct it as it can be very suttle at times to find the problem.