As an experienced "stockbroker"
, one of the things I learned the hard way that countersinking anything into the barrel channel can weaken the forearm of the stock since you are severing the structural continuity at that point. IF you add anything to the stock where you are securing the object to the channel, the
flat washers etc HAVE to be exactly contoured to the channel to prevent excessive edge forces from the washers etc exerting upon the stock. If the washer is contoured to the channel, the force is spread out across the channel accordingly. I've sheared off bipod studs just from recoil with my 300WM when shooting off a concrete bench. Only happened once and probably bad stud but it happened and was a real PITA to remove the broken threaded part. A 300WM at 7.5lbs with a 180 @ 3100 will be in 37 lbs of recoil neighborhood. Shear strength of small screws will be tested.
I spent a lot of professional time in product safety and IF the bipod statement is not in the product manual anywhere, you definitely have a point of discussion with them. I agree with other commenters, telling you verbally is after the fact is a not a defensible position and even it is in a "brochure" the actual manual is where legal positions are "normally" stated IMHO.
If I was the manufacturer, I would be doing whatever I could to make it right even if it was repairing it so it was usable without a bipod. A perceived defect in a product that I made would be something I would want to be corrected so that my reputation remained whole. Crap happens and you would think they would try to help you out somehow to at least make you "whole" again. Heck, years ago, I fell on a walnut stock, my fault, broke it at the tang and Savage replaced it and told me to go hunting. And yes, I have a real soft spot for Savage rifles.
Looking at the stock and not knowing exactly how stable the material is, I would suggest using threaded aluminum rods (2) in parallel into the piece that broke of and then epoxy the other end into the main stock. There are a lot of epoxies out there that will strengthen the connection better than it was before. The rods would definitely provide the structural stability and possibly even allow a bipod in future. The added weight would not be overly significant and probably worth it as well.
I was sickened just looking at the break and I am really impressed with your character dealing with a problem that probably should not have happened in a custom rifle. I would engage them with more discussion on just what they can do for you. If they are washing their hands of it, then that is a huge telling sign of their overall business perspective on customer service. Probably not someone I would want to do business with