One of the requirements set out in the original competition (for a system to convert the P53) was that accuracy would be as good as the P53. How good was that? During the testing a benchmark average Figure of Merit for several P53's was 1.19 feet at 500 yards. For any not familiar with it, the FOM of a "group" is the average deviation of all shots from the calculated MPI. With on the fly ammunition changes (by Boxer) during the testing the Snider was just able to meet the requirement. I have data from a comparison test between Snider and Martini from several years later that has the Snider managing a 1.0 ft FOM at 500 yards, only fractionally behind the Martini. So, the answer is that conversion of the P53 family of rifles to breechloaders left accuracy unchanged. Modern Snider shooters seem to have improved short range accuracy of the Snider by using larger diameter bullets that are "forced" onto the rifling. The Boxer Snider ammunition used a bullet that, while larger in diameter than the P53 service bullet, still required expansion of the bullet upon firing to take the rifling.
Ridolpho