The crown of a barrel, be it rifle or pistol, is an important aspect of accuracy and marksmanship that firearm owners may overlook or take for granted. In military standards, like at the President's 100 marksmanship gunsmith shop at Fort Benning, Georgia, for target standard crown is the 11-degree crown. A properly cut crown will ensure that the circumference of the base of a bullet exits the muzzle at exactly the same time.Diagram at left shows barrel and crown relationship.
|Remington 700 Crown|
The result is the bullet will tip and exit in a manner like a block flying through the air. When it tips coming out of the barrel, it will “keyhole” when it impacts the target; sometimes called tumbling. For competition target shooting that could cost the shooter one point, where one end of the bullet will strike one ring and the other end another ring. Competition shooters have won or lost by one point. Another factor is for hunters in terms of accuracy and kill shots. A keyhole projectile will not go as deep as a trued projectile, thus penetration is compromised; and in turn, bringing down big game with one shot is less likely. For small game shooting, it might mean a missed shot.
There are four crown cuts to choose:
Conventional Factory Crown (flat) - also muzzle-loading blackpowder crowns.
Standard Target Crown
Recessed Target Crown
The Deep Recessed Crown is normally seen on pistols.
The recessed target crown and 11-degree crown – the latter being favored by hunters, competition target shooters, and snipers. The difference between crowns is especially noticeable beyond 100 yards. Other factors are involved past that range, like wind, humidity and air temperature.
As you can see, a burred crown or improperly cut crown makes a big difference upon accuracy. The crown must be cut perpendicular or true to the barrel.
Most crowns are cut on lathes, but Brownell offers the Manson Precision Reamer Muzzle Crown Refacing Kit which allows re-crowning to be performed without a lathe. It comes in 2 pilot or 5 pilot kits, the latter kit ranges for barrels of .22 caliber (.223-.224) to .338 caliber. The 2 pilot kit provides an 11-degree cut for .22 caliber, 30 caliber and .308 caliber.
|Crowned Threaded Muzzle Brake Barrel|
The modified power driver has a spring-loaded adapter that provides a smooth and fast cut to ensure it is concentrically with the muzzle for rifles and handguns. Gunsmiths use the system when barrels are too short for their lathe spider systems. The kit includes a 1/8-inch pilot wrench, 5/64-inch allen wrench, setup gauge, power or manual handle, adapter, instructions and storage case. The manual version has a handle and adapter made for slow (and even) cuts for precise indexing of muzzle brakes. The manual driver is standard and the power driver is available by special order.
If you do not want to pay for the expense of a crown cutting kit (2-pilot kit is $360 not including tax & shipping); get it done at your local gunsmith shop.