There are no set rules by any sanctioning organziation for "factory" rifles. each club basically is using their own rules.
Generally they allow trigger adjustments, recrowning, bedding, and muzzle brakes
. Some say no Coopers, 40x etc or custom shop guns.
Normally specifically not allowed are after market barrels rechambering and truing the actions. Variances to all of the above can be seen though at times.