Author Topic: what kind of crown on a .22 rifle? (Read 544 times)

king nero · « **on:** December 10, 2004, 04:00:02 AM »

straight walls:

a bit of a taper, and a flat surface next to the end of the rifling

here's another one that won't show up as it's bitmap format:
with a 11 degree taper (or what degrees?)

http://users.skynet.be/kingnero/temp/crown.bmp (=> click - safe! small picture)

This is for a project rifle, with (likely) a short barrel (max. 10 inch).
any other suggestions are always welcome, as I have totally no clues when it comes to crowns...

thanks in advance...

gunnut69 · « **Reply #1 on:** December 10, 2004, 07:33:22 AM »

The 2 photos that show up are variations on what's called a target crown. A basically flat crown(rifling terminus) that's recessed to aid in protecting it from dings. The link photo is a ral 11 degree crown. That is an 11 degree taper whose lowest edge is the rifling terminus. It is supposed to help bullet stability when using boat tailed bullets, especially the Lapua rebated variety.. You don't have an example of the standard rounded crown which is in the form of half a doughtnut(must be getting close to lunch). The bore and the outside of the barrel are both lower than the center of the barrel wall. The profile of a lineal slice of the barrel is rounded. It is the most difficult to make and to really do it correctly requires a specially ground lathe bit. so really it's more personal prference.. I kinda like the 11 degree and it works well. Of course the real reason is that it's what I have tools to cut by hand. Anything else and I have to set up the lathe and I find absolutely no difference in accuracy or protection..

king nero · « **Reply #2 on:** December 11, 2004, 01:40:28 AM »

maybe not clearly visible, but that's that donut you are talking about...

OK, thx for the reply. I still have some questions:

Supose I have the means of cutting all those crowns: Which one would you suggest?
I can make my own cutting edge like the pic above: with a bit of grinding in a straight cutting edge it must be possible to make a half-moon with which to cut a crown similar to the one above.

It's easier to make a crown with a taper, but it's going to be impossible to set-up exactly 11 degrees. does it matter that it is exactly 11 degrees, or is everything inbetween (about) 10.5 and 11.5 degrees good as well?

The two pics on top are the easiest to create: center the bore and start cutting.

So, whoch one to use? The donut one is the one which requires the most work, the rest is about the same.

And, after the work with the lathe, does it needs polishing? or other cleaning (sandpaper?)?

Many thanks in advance...

DWARREN123 · « **Reply #3 on:** December 11, 2004, 04:41:45 AM »

I would think it would not matter as long as it is square to the bore, the shapes are to protect the crown/bore area.

king nero · « **Reply #4 on:** December 11, 2004, 05:11:14 AM »

Quote from: DWARREN123

square to the bore

Keep in mind that I'm dutch

does "square to" equals perpendicular?
and if so, how about an 11 degree crown?
(if it isn't, ignore that last comment...)

Iowegan · « **Reply #5 on:** December 11, 2004, 07:51:15 AM »

The real secret with a crown is to have the circumference at the exit point as perfectly uniform as possible. The escaping gasses must apply uniform pressure on the bullet base or it will be unstable. The rest is just cosmetic.

I have an out-of-the-box CZ 22 LR that is a one-holer with a donut crown. I also have a Remington 511 with a custom barrel that has a crown like your second picture. It is also a tack driver.

gunnut69 · « **Reply #6 on:** December 11, 2004, 11:36:30 AM »

I don't believe that any particular crown is better than any other for most work. I've not seen eveidence that the '11' degree crown even helps with boat tail bullets! I believe that a bore circumference that is square with the bore(so the bullet is released completely around at exactly the same moment) is the important part, with protecting that bore terminus being the real reason for a crown! Seems to me that for a 22 any of the crowns you've shown would work with the more proptected versions a bit better, but just for that reason.. Also please note that I have no evidence other than 'they say' that the 11 degree crown does anything at all... It is easy to cut and is usually a bit deeper than other target crowns so protects a bit more?

? In a lathe setup I would center the bore, to a pilot, as most bores are not concentric to the outside of the barrel, and cut a tapered crown with a slight flat area immediately around the bore. A ridge left at the outside of the barrel edge looks fine and may add a bit of protection(not too narrow or it looks weird). In all fairness the first one you pictured looks pretty good although I might deepen the cut just a bit. Muzzle pressure of the 22 rimfire is fairly low so almost anything will be just fine.

king nero · « **Reply #7 on:** December 12, 2004, 02:37:30 AM »

OK, many thanks!
I've read a whole lot of useful information here:
Done with theory, now it's time for the realisation.
I'll get back here when it's done, or when I need more advice, whatever comes first...

gunnut69 · « **Reply #8 on:** December 12, 2004, 11:52:56 AM »

GReat! Let us know how the project works out!!