By Jeff Johnston
The Question: Will Damage To a Rifle's Crown Hamper Accuracy?
If you're like me, you're nutty about preventing your rifle's crown (where the barrel's rifling is exposed at the terminal end of the muzzle) from being damaged, because it's commonly believed that crown damage can cause a bullet to exit a barrel erratically, thereby ruining accuracy. But I want to know exactly what happens when you nick your rifle's crown with a cleaning rod, grind your muzzle on gravel and dirt, take a rat-tail file to it or accidentally slip and cut the crown off entirely with a hacksaw. At worst I knew I'd ruin a few barrels and confirm what most of us already believe. But perhaps I'd find I don't have to spend the whole hunt worrying about my barrel's precious crown.
With the accuracy of each undamaged barrel recorded, one barrel was dedicated to each of four different possibilities of barrel-crown damage. One barrel was used for two tests.
Damage ranged from common causes like cleaning your rifle from the muzzle end (mild damage), to major damage, to extreme crown desecration that should never occur to a firearm and could be dangerous. After damaging all barrel crowns, the rifles were fired again in the exact same manner as the pre-damage test, with the same ammunition, from a Caldwell Lead Sled to reduce human error. A 50-yard, indoor range was chosen to reduce variables such as wind and fluctuating temperatures. Results were compared to the original groups to determine if crown damage influences accuracy and point of impact (POI).
Nonetheless, if your barrel's crown is damaged, your rifle may not be ruined: In most cases, after damage, the first shot in particular and first group on average were the most erratic. But in most cases, as more groups were fired, the groups began shrinking and migrating closer to original point of impact. If your crown is lightly damaged (the barrel is not bent nor the muzzle obstructed), fire a box of cartridges through the rifle to see if the bullet's natural honing action repairs the barrel to a usable state. If it is not satisfactory, take it to a gunsmith or have it rebarreled.
Therefore, baby your barrel! Do not clean it from the muzzle end-clean it from the chamber end. Keep your muzzle away from rocks and grit, and of course, whatever you do, refrain from cutting your barrel off with a hacksaw. The crown is best left pristine!