I have some questions about accuracy that I don’t understand.
Why is accuracy increased when the ammunition has a straighter casing, as opposed to a more tapered one?
Why is accuracy increased when a rotating bolt has more smaller lugs, as opposed to lesser and bigger lugs?
I am not sure that those aspects have been conclusively linked to precision. Barrel and ammunition quality seem to be the most significant issues- unless you are interested in minutia.
There’s several ways to improve on accuracy in a rifle:
Keep hot gases from entering the chamber from back pressure. A tight chamber with a very solid bolt lockup keeps the gas pressure more consistant.
Use consistant ammunition. Little deviations in charge can lead to different presssures and different velocities. Bullets exiting a barrel at different velocties leads to scattered groupings.
Use a quality barrel with a consistant crown. Usually, only the last few inches of barrel rifling are the determining factor of consistant spin. This is why there are guys that can shoot playing cards with a snub nosed revolver at 100yrds.
Shorter, fatter cartidges tend to have more consistant burns. The ideal burn chamber is a sphere…so the closer the cartridge design is to having equal length and equal width the better the burn rate.
There are a lot of little factors that determine accuracy. I’m not sure how a straight walled case effects accuracy. A higher number of bolt lugs would create more surface contact area in the chamber because a common assault rifle bolt can only rotate so far to turn closed inside the chamber. Most only have 3-5mm of contact surface per bolt. So, a 7-lug would have 3mm(x7) of contact surface, while a 4-lug would have 3mm(x4) of contact surface. This would lead to a tigher seal. The downside to more lugs is that they have to be thinner, so they are less durable then fewer lugs which can be thicker and more durable.
…everything is a compromise.