Heavy lies the rifle that wears the crown.

[MajorDanger]

Talking about muzzle crowns. I figured it would be a good topic of conversation. What are your thoughts on different crown types for your rifles?
Target crowns, recessed crowns, flat crowns, counter-boring?
What works best for you, and why?
(I don't know anything about crowns other than as long as they're even where the bullet last contacts them, they'll do their job)

Thoughts?

 

[wogpotter]

Essentially "horses for courses".

I had a custom rifle for target work it had the recessed target crown. It seemed to work as I regularly shot 1/3 MOA groups.

I have 2 rifles with "muzzle devices". This removes the need for impact protection as nothing can get down inside the devices to contact the actual crown. Because of that the crown isn't recessed but it is checked periodically for crud that forms down inside the bigger hole.

My B/P muzzle loader has a beveled crown so that it doesn't cut patches when loading.

Each is suited to the task it does even though it may nor excel at others.

 

[Bart B.]

Some 'smiths refer to the crown as the edge of the rifling at the muzzle while others call the entire front of the barrel the crown.

Most 'smiths catering to competitors call the inner edge where the rifling angled out at 30 to 45 degrees past its groove diameter a few thousandths inch the crown. The rest of the muzzle end to the outer diameter is called the face. Face angles or shapes differ based on objectives the barrel maker and/or fitter chooses.

Some years ago, some competitive shooters took a very accurate barrel and ammo then faced its from from zero degrees to about 20 degrees in 1 degree steps. They shot test groups at each face angle. The groups shrunk from small to tiny then back to small. Tiniest groups were when the face angle was between 10 and 12 degrees. Eleven was therefore declared the magic number. They crowned the rifling with a half inch brass ball charged with lapping compound to deburr the sharp edges left by facing the muzzle.

More important than the face or crown themselves, is how they're centered on the bore. A centering tool with its plug .0001" smaller than bore diameter is put in the muzzle, another at the breech end of a barrel blank. The blank is turned down an inch or so back from each end so the outer diameter is equidistant from the bore all the way around. With the breech end in the lathe headstock, the muzzle end's centered in a steady rest and the muzzle faced to 90 degrees removing minimal metal. Then the rest is set for the 11 degree face and the tool tip is moved out from bore center. That centers the face on the bore. Finally, the crowning ball's charged and gently pushed into the bore lapping away the edges of the rifling a few thousandths out past groove diameter at some angle.

Recessed and counterbored faces/crowns have been used mostly for a marketing ploy. They're no better than standard ones but are impressive and important to some. And they're not easy to clean out.

Pulling a bronze bore brush back into the muzzle's crown will smooth their sharp edges over time. I've never seen any loss of accuracy by doing that once for every 5 to 10 shots fired between cleaning cycles.

 

[MajorDanger]

Thanks guys!

I see so much stuff on the topic, but rarely all in one place.
Now, I have a 30.06 and it looks like it wouldn't have enough space on the face of the muzzle to do anything fancy with it. Are these step crowns and things more commonly found on bull barrels or varmint barrels? I understand the gimmick of the recessed crowns or counter-boring. They say that in setting your crown back into the barrel a little ways, it protects the crown and rifling from damage if you were to knock your rifle on something.

Another thing I've wondered, is aside from the crown being even, and perpendicular to the bore, is there really any more effect to having a specific style of crown? Or, do different crowns produce different effects? The gas escaping evenly from all sides of the bullet the moment it leaves the barrel is the desired effect of any crown, but do any of the different styles do anything more than that?

Thanks for all your help by the way. It's just something I've been curious about.

 

[Snyper]

Another thing I've wondered, is aside from the crown being even, and perpendicular to the bore, is there really any more effect to having a specific style of crown?

No, as long as the crown is concentric, the details don't matter at all

 

[Bart B.]

I doubt one will notice any difference in how the muzzle is shaped until accuracy is under 1/2 MOA through 600 yards.

The angle muzzles are faced effects the directions gas escapes around the bullet's heel moving a few times faster than the bullet. If the gas escapes such to alter the bullet's path the least with an 11 degree angle face, that must have a positive effect with minimal change to the bullets trajectory. It's similar to jacketed hollow point bullets having more perfectly shaped heels than hollow base ones. Their more uniform dimensions let gas escape more evenly around the heel tipping the bullet and changing its direction less when it goes past the crown.

 

[T. O'Heir]

As long as they're even where the bullet last contacts them is pretty much all anyone needs to know. What it looks like doesn't really matter.
Typical sporting rifles' muzzle is that rounded shape, but a square flat end will do the same thing.
And yes, steps and counter bores are usually on heavy barrels, but some milsurps with worn rifling near their muzzles can be resurrected with a counter bore. Like Bart says, there's a lot of marketing involved, but the angles don't make any difference.