Bolt sleeving is not new to the gunsmithing industry. It was tried and used by other smiths before I came along. What set me apart has been the reamer/mandrel I designed with interchangeable bushings to center the mandrel in the action and recut the bolt bore raceway to the same diameter. This then allows bushings of the same diameter front and rear. As seen on the action-truing page the mandrel is then used to align the action in the action jig.
In the picture above, is a setup from my bolt sleeving video. It shows the 0.0084 cant that is induced on a new Remington long action. This cant will tip the top bolt lug 0.0019 off the top action lug seat. This happens whether the action has been trued or not. It?s caused by the cocking piece sear and the upper trigger sear holding the firing pin in the load position. With about 22 lbs. of spring pressure on the sear faces and behind the rear bridge area of the bolt, the bolt is pushed up in the back. The fulcrum point is the rear bridge and the bolt angles down ward until it rests on the bottom of the front bridge. The shorter the bolt and action the greater the top lug is tipped off the action lug seat for the same amount of cant at the back of the bolt. In the book RIFLE ACCURACY FACTS, this condition in an action can result in mechanically induced vertical stringing.
What the sleeves do is hold the bolt level and centered in the raceway. Now when the firing pin is loaded the bolt doesn't cant and tip the lug. Along with this you don't have a bolt falling in the action when the trigger sear is released. The bolt falling is a bolt face moving. The ignition of the primer/powder is started before the bolt hits the bottom of the action. This creates another vibration to the barrel that you have to deal with in developing a load. It's also inconsistent. Sleeving the bolt creates a very consistent ignition system.
When I do the final fitting of the sleeves on the bolt, they are made elliptical. This allows free cycling of the bolt because we have the original clearance plus a few thousands, but as you close the bolt, it cams into alignment and holds the bolt in a repeatable position. This is why I recommend double sleeving not only for competition rifles, but varmint and hunting rifles also.