Bolt body is the correct term. PTG sells oversized bolt bodies. You will need to know the bolt raceway diameter. Therefore you will have to measure the I.D. of the rear action ring to find the dimension that will determine the bolt Outside Diameter. A machined inspection rod might work. You might be able to use shim stock around the current bolt body. Some Telescoping gauges if you have them.

Once you find out the exact inside diameter, subtract .002" and that will be your bolt body outside dimensions.
I have heard of aftermarket bolt bodies changing the trigger timing. It could go either way by improving or decaying the trigger hand off.

Many believe that trying to fit a bolt body tighter on a Savage is a waste of time. I prefer it but can't prove any benefits except my perception. If you are looking for a smoother bolt travel the oversize bolt handle can be the root cause. Try not to push the bolt handle in a way that it cocks the bolt. push forward while centering the bolt. I have used a hone to smooth the lug raceways out as most of the time they are scored pretty good from the machining process. That has smoothed out more than one actions bolt travel.

edited to remove bolt fluting recommendation.