In my experience there are 5 things that needs to be corrected on a rifle to get it to shoot better.
These are basic corrections what I do on standard factory rifles that comes into my shop with the ailment of ‘ not grouping’. This is to some degree applicable to custom build rifles but with custom build rifles I always start with blueprinting the action as standard practice as well as the bedding. So on my custom build rifles these problems does not exist. Then only reloading, scope quality and shooter error remains.
The following are 5 mechanical problems on a rifle that causes inaccuracy.
Most important, I have found, is the barreled action should be bedded correctly. Either with just epoxy or rather with epoxy and aluminum bedding pillars. In my case I do an aluminum bedding block under the front section of the action and a 16mm pillar in the rear under the tang of the action.
The bedding material should extend to about one inch under the barrel to support the knox of the barrel. I have found that to work in most cases. In very rare cases I had to remove that section of bedding under the knox to get the rifle to shoot better.
In cases where the taper of the barrel starts where the action stops, I don’t do bedding under a tapered knox as I have found that to be detrimental to accuracy.
The stock and action should form a unit, both supporting each other with the bedding material strengthening the whole setup.
I also like to use an epoxy that can flow easily as that ensures all the gaps get filled properly.
I have had many rifles that has been bedded but done incorrectly through the use of a putty type of bedding material. Putty type bedding materials is very difficult to press in correctly without creating stress in the action.
Another fault is tightening the action screws after the bedding has been done but before the epoxy has hardened. This only serves to induce the original error and doesn’t fix it.
The action screws should be kept loose and only used to guide the action into the stock with the bottom metal held in place.
The action holes in the stock should be drilled out after bedding, to remove unwanted epoxy, so that the action screws fit easily through. They should not bind at all.
On Remington actions and actions with similar recoil-lugs, the bedding should only touch the rear of the lug.
Something else to note is that even the trigger may need to be reset after bedding. The tang of the action could have been bent before bedding and now better aligned with proper bedding. This will influence the trigger pull.
2. Barrel Free-Floating
The barrel should be free floated freely. Rather to big of a gap than too little. The free-floating can really only be done after the bedding has been done.
If the contact area between action and stock is not correct, then as the barrel is free-floated the barre will only sink in deeper into the channel until the action bottoms out in the stock. A lot of times this sinking in is too much.
So rather fix the bedding first and then do the free-floating of the barrel.
3. Action Recoil-lugs and Bolt must be lapped
Proper contact between recoil lugs of the bolt and action is a must, as improper contact creates a barrel vibration before the bullet leaves the barre and causes inaccuracy.
A better alternative to lapping is to blueprint the bolt and action.
4. Re-cut the Crown
Very important to make sure the crown is perfect perpendicular to the bore. That’s the most important point. The shape of the crown is not that important.
5. Scope-rings must be lapped
To avoid putting pressure on the scope tube the rings need to be lapped to ensure perfect fit and alignment.
Very important to remember that the bedding must be done first then the barrel channel free-floating, before the scope-rings are lapped, to eliminate the incorrect movement of the action. The stock will influence the scope alignment and also the barrel channel clearance between barrel and stock.