where did you get this crock of malarkey?
Malarky?
Go buy a reloading manual, a bullet catalog, and a few firearm data books.
See how many guns can use the same bullet for reloading.
See which guns have the same twist barrel and bore diameter.
It will take a while to make an exhaustive comparison, I’ve been at this for over thirty years, professionally the last twenty.
Either you are just hostile, or ignorant, or did not understand my post.
I thought it was pretty clear.
An easier example for you, 30-30, 308, and 30-06 are all .308 rounds, standard bullet weights vary, but they can all use the same bullet in the lighter weights.
They may also be made with the same twist rate.
All of these calibers have been used in semi’s and bolt actions, the 30-30 is also common in lever actions.
A recovered bullet cannot be PROVEN to have come from any specific model or type of gun without additional information, such as having witnessed it being fired.