Customer dropped off a .257 Custom model with accuracy issues. It 'patterns' with Weatherby factory ammo. It's an older rifle but a safe queen, it hasn't had more than 3 boxes of ammo down the tube if that. Bore is clean. It has a Bausch & Lomb scope sitting in a Leupold windage mount. The mount is tight, rings were retorqued to spec. Action screws were torqued to 35in/lb per factory spec. The Mark V action has a threaded recoil lug that is secured by the front action screw.
The elevation knob on the scope is at max CW just to get it on paper. Windage adjustment is nominal. The group size is around 6" at 100 yards when shot from a rest with factory ammo. Weatherby only specs 1-1/2" groups which would be a vast improvement from what it is now. Weatherby uses a 'pressure pad' which is just a bump in the stock barrel channel to stabilize the thin barrel. This concerns me as far as shooting from a rest but the owner has similar results shooting prone without a rest.
I believe the problem is with the stock and the reason I am suspect of it is when you tighten either action screw by itself, the opposite end of the bottom metal sits proud of the stock. Installing the second screw results in distortion of the bottom metal though it's not visible and function isn't impaired.
What I suspect is happening is that the receiver is being pulled down into the stock and bowing the barrel upwards. I haven't had the opportunity to set the rifle up and put some DTI's on it to make measurements. I'm researching the issue at the moment, I've read mixed results in regards to bedding the Mark V action, some say bedding one makes things worse, some say floating the barrel makes things worse as well.
Intuition is telling me to install pillar(s) & bed it to remove all the stress from the action, remove the pressure pad from the forearm and simply bed that area to provide neutral barrel contact. Unlike a Remington action, there isn't much room for a pillar at the bottom of the recoil lug pocket. The bottom metal without fasteners sits level in the inlet so bedding it would be an improvement.
I'm looking for input at this point hopefully from someone who has worked on the Mk V.
The elevation knob on the scope is at max CW just to get it on paper. Windage adjustment is nominal. The group size is around 6" at 100 yards when shot from a rest with factory ammo. Weatherby only specs 1-1/2" groups which would be a vast improvement from what it is now. Weatherby uses a 'pressure pad' which is just a bump in the stock barrel channel to stabilize the thin barrel. This concerns me as far as shooting from a rest but the owner has similar results shooting prone without a rest.
I believe the problem is with the stock and the reason I am suspect of it is when you tighten either action screw by itself, the opposite end of the bottom metal sits proud of the stock. Installing the second screw results in distortion of the bottom metal though it's not visible and function isn't impaired.
What I suspect is happening is that the receiver is being pulled down into the stock and bowing the barrel upwards. I haven't had the opportunity to set the rifle up and put some DTI's on it to make measurements. I'm researching the issue at the moment, I've read mixed results in regards to bedding the Mark V action, some say bedding one makes things worse, some say floating the barrel makes things worse as well.
Intuition is telling me to install pillar(s) & bed it to remove all the stress from the action, remove the pressure pad from the forearm and simply bed that area to provide neutral barrel contact. Unlike a Remington action, there isn't much room for a pillar at the bottom of the recoil lug pocket. The bottom metal without fasteners sits level in the inlet so bedding it would be an improvement.
I'm looking for input at this point hopefully from someone who has worked on the Mk V.
