Barrel crown on the cheap

[riverdog]

Picked up a relatively inexpensive Kel-Tec SU-16CA 5.56 rifle. First thing I did was clean it and realized the barrel crown was awful with burrs grabbing the patch. This made me look at getting something to cut a new crown or chamfer the muzzle and I found 45° Chamfering Cutter. Hmmm. . .

My question: Is this a good way to go to clean up the muzzle? Looks fairly straight-forward, but the devils in the details. Any thoughts or experience with this tool? TIA

 

[Savage99]

I have had very good results using a Dremel #952 wheel. I put it in a variable speed drill. Place the bit in the barrels muzzle, start up the drill and then pull it away.

Here is another way to cut a crown.

http://www.youtube.com/watch?v=b43odFm0mrI

 

[7.62 Nato]

Here you go http://www.youtube.com/user/MidwayUSA#p/search/8/OorpZlG28fI

 

[riverdog]

Thanks much. That looks doable.

 

[RippinSVT]

I have also heard of people using a round-head brass screw/bolt and chucking it into a high-speed drill and sort of "polishing" the muzzle where the rifling ends at the crown.

 

[rcmodel]

The round-head brass screw and valve grinding compound in a drill has been used for crowning since rifling was invented. Maybe even before that.

Use the screw in an electric drill and keep it wobbling around in all directions as it cuts the crown.

That insures a completely even crown all around, and wear on the screw head cutting a ring that will not cut evenly..

IMO: You simply cannot do it free hand with a grinder stone in a Dremel tool and make it perfectly even.

rc

 

[zxcvbob]

I've done the brass round-head screw and JB bore paste thing before. It works but is slow. I think fine valve grinding compound (Clover) is the right abrasive rather than JB. I would never do it freehand with a grinding stone.

 

[rcmodel]

+1

Don't waste your time fooling with JB Bore Paste.
It is hardly abrasive at all, and won't work.

Go to the auto parts place and buy some Loctite or Permatex valve grinding compound.

http://www.google.com/products?hl=e...esult_group&ct=image&resnum=3&ved=0CB8QzAMwAg

rc

 

[riverdog]

Are there any issues concerning the Kel-Tec SU-16CA chrome lined bore? TIA

 

[Heavy D]

+1 for the valve grinding compound. I used it to for lapping the slide to frame fit on my 1911 as well.

 

[amlevin]

The importance of the crown is topic for many late nite discussions. It is generally accepted that a proper crown not only has a sharp edge when the rifling/bore ends but also is precisely 90 degrees to the centerline of the bore. Most target and sniper rifles use some variation of this. Military sniper rifles, like the M-24 have a "recessed" crown. The crown, whether it be square or an 11 degree crown, has a lip at the outer circumference to protect it from the ravages of a combat environment. The key is to provide an equal release of gasses, the full 360 of the bore, as the bullet leaves. If this release is unequal it will "kick" the bullet as it starts its flight. Altered path or wobble can occure due to this.

As for gaining accuracy on the Kel-Tec, just about anything will help. This rifle is not real high on the list of accurate rifles. Fun, yes. Accurate?????

 

[evert]

The brass-screw and grinding compund works well, but does not give totally 90degrees to the bore. anyway, it ususally shoots great.

a note on the piloted cutters from brownells: the pilots they sell almost never fit the bore well, and a good pilot/bore-fit is essential to get a chatter-free cut.
when using the brownells-cutters, i always lathe-turn pilots to fit the specific bore i am crowning.