This Remington M770 benefitted from recutting the crown. The right-hand group is before recutting; the left-hand group is after.

A recessed or target crown will clearly show the blast marks from the escaping gases. So, most of the time, will an unblued barrel. A rounded sporting crown on a blued barrel will disguise the evidence. What you hope to see are concentric blast marks where the gas exits at the rifling grooves, and the white-out will tell the tale. I fired three shots, and the white-out clearly showed the blast marks--and showed that they were irregular, obviously kicking the base of the bullets to one side.

No problem. We broke out Brownells' crowning kit, which resembles a handloader's case-chamfering tool except with a spud that fits the muzzle and guides the tool. You have to take your time, and as you turn the handscrew, make sure you stop in a different place with each revolution so as to avoid metal buildup.

My last group prior to recutting the crown was, honestly, worse than the average to that point, but it had no called flyers. It was a bit over 1 1/2 inches, with the average--to that point--maybe a quarter-inch less. At this stage the point of impact was a bit high and right, so I came left eight clicks, more to keep the groups separate than for concern about zero. After crowning, I fired the next group into the same target using the exact same load. The improvement was dramatic. The first three shots after recrowning were almost touching, a very tidy group of less than a half-inch. This meant that the simple process of tidying up the crown reduced group size by more than half.

I wasn't shooting at 200 yards, so I don't honestly know if this rifle would have produced smaller groups at that distance than at the 100-yard distance I was shooting. I suspect it would have. An irregular crown had clearly been impeding the accuracy, and it's likely that the bullets would have eventually gone to sleep in flight and delivered the accuracy the barrel was trying to produce. That's speculation. It is not speculation that recrowning the barrel cut the average group size of this rifle from an acceptable 1 1/4 inches to a spectacular half-inch.

Out-of-the-box muzzle crowns are often imperfect, and it is amazingly easy to damage a crown. You can do it by placing your rifle muzzle-down in a vehicle and grinding the crown on dirt and debris. You can also do it through careless cleaning. Checking the crown, and fixing it when required, is just another tool in the little bag of tricks that accuracy-conscious shooters carry around.