crowning

[flounderman]

I have a 6.5 magnum barrel that suddenly quit shooting. it appears someone battered the crown. I have a 6.5-257 reamer with a solid pilot. I put the pilot in the muzzle and turned it by feel and it doesn't look bad. has anyone tried crowning with a chamber reamer. I haven't had a chanch to test the rifle yet so I don't know how successful this experiment was.

[B R Shooter]

You probably did about as good a job as can be done without the barrel in a lathe. The piloted reamer would center itself well and should make a nice tapered crown.

[shotman]

all the old rifles used the crown. Now all use a square cut or slight recess. so Looks like as long as there is no damage to end of the barrel it dont matter ???

[303Guy]

They say tests have shown an 11 degree crown is best. Making it square with a recess is much easier and more forgiving and it's what the varmint barrels have. I wonder how much difference it really makes.

[405]

Interesting topic!
I don't know if anyone knows the exact angle for the best or most accurate crown. My understanding is that the 11 degree was settled on as the best compromise. An extremely shallow angle would seem counter-productive considering how uncertain the uniformity would be at the instant of gas escape as the bullet clears the bore. Plus the tooling required to cut a perfect crown at an extremely shallow angle would be problematic. Conversely, a negative angle crown would expose the crown edge to handling damage- a "thin", fragile edge at the crown. Plus, gas pressure and/or erosion could start damaging that thin edge after repeated firings. So the 11 degree was settled on. Easy to cut or ream, provides an oblique angle edge that is durable and, by its design, is somewhat rebated thus protecting the crown edge from handling damage. And, no matter the angle, the most important aspect of a crown would be creating as nearly perfect and concentric a 90-degree-to-bore-axis gas/bullet escape edge as possible.

[John 242]

You guys ever heard or seen the old trick of fixing a crown with a brass screw and lapping compound?

I've read about the technique in a couple of old gunsmithing books I have and watched a video by Larry Potterfield on Youtube doing the same thing.

Might not be a "target" grade crown, but apparently it works, which leads me to wonder if the exact angle isn't so important as compared to the crown being free from damage and cut relatively evenly.

I'm not saying I'd want this 'garage gunsmith' crown on a rifle I taking to the Nationals, but for fixing a damaged garden variety rifle, it might be adequate. I'd love to see the actual results on paper of a 11-degree crown versus a crown cut with a brass screw.

In case I lost anyone, the brass screw procedure is as follows:

After cutting off the damaged portion of the barrel if necessary-

- Begin by using a 10-inch smooth mill file to dress the muzzle in order to remove any damage and to file it square to the barrel. Finish dressing the muzzle with sandpaper to remove the file marks.
- The end of the rifling is touched up with a round-headed brass woodscrew or a brass ball on a shank coated with lapping compound, spun by a drill. Rotate the screw in increasing circles to prevent from wearing the screw unevenly. Wobble the screw around to remove any burrs from the end of the rifling.

[KCSO]

Lapping is what you do to finish a crown, you want it smooth as you can get it. I have the cown tools from brownells and have used them for damaged barrels but my favorite method is to take the barrel off an do the crown in the lathe. Te closer you get it to concentric and the smoother it is the better the gun shoots. I personaly see no difference between recessed, 11 degree or the old round crown as long as they are done right. I want the crown concentric to the bore not the outside of the barrel and I try to get under .0005 if I can.

[John 242]

Found it, check it out-
http://www.youtube.com/watch?v=OorpZlG28fI&feature=BFa&list=PL64B5191255FC025B&lf=mh_lolz

[Ben_51004]

John 242 is on the ball with this one. Most important thing is to square the end of the muzzle perpendicular (sp?) to the bore line. Then use a fine compound (I have used fine CLOVER valve-grinding compound; extra-fine is better), a fairly large round head brass screw, and move the screw in a "figure-8) type of motion as you finish the crown. Use light pressure and slow speed on the drill. This process can work very well; if you go slow and inspect often it's nearly impossible to screw up. When finished, clean up by pushing patches FROM THE BREECH ONLY, and wipe carefully. You DON'T want any of that grit compound in the bore of your firearm when you fire it!! You can touch up the bright ring with some cold bluing if you want to, but if you're careful you don't really need to in my opinion. ~Ben~

[ASSASSIN]

Here is a picture of how my crowns look after setting the barrel up in the lathe and cutting a new crown or recrowning an old barrel...
http://i193.photobucket.com/albums/z132/HonkerHunter_photos/308%20and%20264X444%20Improved/007.jpg


I have experimented with many different types of muzzle crown and have not forund one to be any better than the rest...

What is important though is that the crown be cut concenrtic to the bore. Other than that, it does not matter if the crown is cut at 3, 9, 11, 15, 18 or even a flat 90degrees....

A

[felix]

True. The warehouse BR tuning experiments have proven this many times over. Cutting square is the key, and not the funnel angle per se. ... felix

[Wolfer]

John 242
I used this method on an 8mm Mauser that I cut the barrel off on. Instead of brass I used a stove bolt and fine valve grinding compound. Could be wrong but I read about using the stove bolt in Roy Dunlaps book I think. Anyway it worked great and the gun shot great. I personally wouldn't hesitate to use this method on any gun I own.

[zuke]

I've used a dremel ball grindstone turned slowly in a drill while squirting water on it to carry away any grinding's.

[MBTcustom]

Zuke, how did you manage to keep the crown absolutely square to the bore?

[303Guy]

ASSASSIN's method requires quite a bit more skill than a recessed 90 degree crown. I think therein lies the crunch. A better or prettier crown requires more effort.

[ASSASSIN]

On factory handgun/revolver barrels & rifle barrels, do they pay attention to making the crown perpendicular/square to the bore?

What are some methods of checking the crown?

I wonder how many could be improved upon and shoot more accurately.

No, the factory's are not to concerned with the concentricity of the crown. You MIGHT find one out of every 20-30 that are pretty close, but with barrels being mass produced, that's about all you can expect...

I have seen a lot of barrels that would not do better than a couple of inches at 100 yds., and by cutting off the last 1/2" to 1" at the muzzle and cutting a crown that is cut true to the centerline of the bore, a lot of these same barrels would start shooting and inch or less, with no other work being done, other than the crown being correctly cut...

Nothing is carved in stone though. I have also seen some if the worse crowns out there and that barrel still shot very well. Sometimes, if just doesn't make any sence....