Re-crowning a cut barrel?
- Thread starter BerdanSS
- Start date
You can crown a barrel with brass round head screws and valve grinding compound that your local hardware and auto parts stores should have in stock.
Crowning a Barrel
Crowning a Barrel
Huffmanite
New member
LOL, if you reload and use Lee's brass case tool to trim brass you can use it. Usually you just need the next bore size spindle on the trimmer. For example, if the bore is 30 cal, then use a 7mm/.284 spindle. Spindle will fit loose in bore, so you will need to shim it to take up slack, so it will not wobble. I use either aluminum from a coke or beer can, or brass shim stock....this will also protect rifling in bore. You can chuck the trimmer in a drill if you have a large enough drill. I don't, just spend 15-20 minutes hand turning the trimmer. Helps to apply lub to spindle and face of muzzle.
Huffmanite
New member
I've tried a stone without any real luck a few times. Basically, ones I've tried were not not well made.....were out of round so to speak.
Using a large round screw head, Brass one, with automotive valve grinding compound available at an auto parts store can work decently. A "carriage" bolt head can work too with valve grinding compound.
Using a large round screw head, Brass one, with automotive valve grinding compound available at an auto parts store can work decently. A "carriage" bolt head can work too with valve grinding compound.
I've used a round ball (or similar shape) stone to rough in a crown on many cut barrels, over the years. After that, a round head brass bolt, of the appropriate size and contour, with valve grinding paste, to final contour and polish the crown.
This works very well, if a few rules are followed :
1) Make sure the stone used is concentric (doesn't wobble when spun in a drill). That is easy to check visually, of course. Buy a GOOD quality stone - it will be worth it. A medium to fine grit stone will do - skip the really rough grade stones.
2) The brass bolt WILL be concentric, in all cases, if it is of good quality. Again, check this visually, before use - don't use a non-concentric bolt. Also, size the bolt head to the barrel/ bore size. You really want a true half-round bolt head, in order to do a nice recessed crown, but that is up to you.
3) BE SURE to plug the barrel tightly, right up to the muzzle, to keep the valve grinding paste OUT of the barrel (and away from the rifling).
4) If the bore of the barrel is centred (concentric in the barrel), then the crown you create will automatically be concentric. Even if not, the crown WILL be concentric to the bore, which is what's most important.
5) BE SURE that the cut end of the barrel is SQUARE. USE an engineer's square, or other ACCURATE tool, to determine this. "Eyeballing it" is NOT good enough. If you start with a slanted cut, then the crown will be slanted - and the barrel won't shoot properly. THIS IS CRITICAL. If you screw this up - the rest is wasted effort !
6) GO SLOW. Take your time and be careful. If you take care to cut a good, clean rough crown with the stone, then the finished crown will almost certainly be good. If you scar the cr#p out of the end of your barrel, via ham-handed technique with the drill, then the end result will look like cr#p. Do a good job....and it will look "professional".
7) Polish the crown, using the bolt and grinding paste, thoroughly. The smoother, the better. Polish it until it shines like a mirror. That will eliminate almost all chance of leaving a small nick, which would affect accuracy.
This works very well, if a few rules are followed :
1) Make sure the stone used is concentric (doesn't wobble when spun in a drill). That is easy to check visually, of course. Buy a GOOD quality stone - it will be worth it. A medium to fine grit stone will do - skip the really rough grade stones.
2) The brass bolt WILL be concentric, in all cases, if it is of good quality. Again, check this visually, before use - don't use a non-concentric bolt. Also, size the bolt head to the barrel/ bore size. You really want a true half-round bolt head, in order to do a nice recessed crown, but that is up to you.
3) BE SURE to plug the barrel tightly, right up to the muzzle, to keep the valve grinding paste OUT of the barrel (and away from the rifling).
4) If the bore of the barrel is centred (concentric in the barrel), then the crown you create will automatically be concentric. Even if not, the crown WILL be concentric to the bore, which is what's most important.
5) BE SURE that the cut end of the barrel is SQUARE. USE an engineer's square, or other ACCURATE tool, to determine this. "Eyeballing it" is NOT good enough. If you start with a slanted cut, then the crown will be slanted - and the barrel won't shoot properly. THIS IS CRITICAL. If you screw this up - the rest is wasted effort !
6) GO SLOW. Take your time and be careful. If you take care to cut a good, clean rough crown with the stone, then the finished crown will almost certainly be good. If you scar the cr#p out of the end of your barrel, via ham-handed technique with the drill, then the end result will look like cr#p. Do a good job....and it will look "professional".
7) Polish the crown, using the bolt and grinding paste, thoroughly. The smoother, the better. Polish it until it shines like a mirror. That will eliminate almost all chance of leaving a small nick, which would affect accuracy.
First, how accurate do you want/need it to be?...
Second, is this likely just a one-shot deal, or do you think you'll be doing other rifles down the road?
You can rent tools, from places like 4D:
http://www.4-dproducts.com/tools.php?group=
I purchased a PTG 11-degree crowning tool, and did one of my barrels with perfect results. But, no reason to buy tools (even $75-$100) if it's a one-shot deal.
If the barrel is "deserving"- meaning it's match-grade and sub-minute accurate, it's probably better to just take it to a smith, most charge $75-$100 for a cut/crown job.
Or, if it's an inexpensive rifle and anything will be better than what it is, use a screw like Larry Potterfield...
Second, is this likely just a one-shot deal, or do you think you'll be doing other rifles down the road?
You can rent tools, from places like 4D:
http://www.4-dproducts.com/tools.php?group=
I purchased a PTG 11-degree crowning tool, and did one of my barrels with perfect results. But, no reason to buy tools (even $75-$100) if it's a one-shot deal.
If the barrel is "deserving"- meaning it's match-grade and sub-minute accurate, it's probably better to just take it to a smith, most charge $75-$100 for a cut/crown job.
Or, if it's an inexpensive rifle and anything will be better than what it is, use a screw like Larry Potterfield...
Wheeeeel....I put it this way. It's a 2004 Muzzle loader that I paid $50 for. I bought it to do a project I've been wanting to do for a while. The barrel was cut from 24" to 18" so hence the need for crowning. The muzzle was just rotted out GONE anyway, but when I cut it off I exposed crisp, new looking rifling. 90% of it's use will be on deer and hogs anywhere from 5-75 yards.
So I don't feel the need for the care that was put into my air gauged, match grade Douglas barrel. It, for the time being at least will be a one shot deal.(maybe another one year or two down the road)..although my buddy has already asked me to do one for him with his Traditions Tracker. That being said, the way I am I'll probably put more time in on it than necessary making it as good as it can get without the $120 tool. I just spent an hour and a half grinding and polishing on four set screws I used to replace the missing ones for the scope mount holes... until they were all the exact same and fit the contour of the receiver perfectly.
Yes I'm nuts
That tool place is a really great site though, never knew something like that existed. Thanks for posting it!
So I don't feel the need for the care that was put into my air gauged, match grade Douglas barrel. It, for the time being at least will be a one shot deal.(maybe another one year or two down the road)..although my buddy has already asked me to do one for him with his Traditions Tracker. That being said, the way I am I'll probably put more time in on it than necessary making it as good as it can get without the $120 tool. I just spent an hour and a half grinding and polishing on four set screws I used to replace the missing ones for the scope mount holes... until they were all the exact same and fit the contour of the receiver perfectly.
Yes I'm nuts
That tool place is a really great site though, never knew something like that existed. Thanks for posting it!
A friend of mine crowned his barrel with a marble epoxied to a bit shank. Then he put emery cloth on the marble and chucked in a hand drill. He gets exceptional accuracy for the gun... I can't recommend that procedure as it is so unusual. But it's hard to argue with success. Of course, he only did it to the one gun.
Well...I did it. After truing the muzzle with a square, short piece of angle iron and a flat file.....I used the grinding ball, a 3/4" fine grit. It came out great, better than I could of hoped for
I then laid out a line all the way around and on the front of the muzzle. Next took a good flat file and knocked the edge off between both lines to give it a nice factory looking chamfer. Thanks everyone for you suggestions and tips
Now for polishing...I cant find a brass bolt big enough anywhere. This is a .50 caliber. found some that would be great for a .30 caliber rifle...just not big enough for the .50
I then laid out a line all the way around and on the front of the muzzle. Next took a good flat file and knocked the edge off between both lines to give it a nice factory looking chamfer. Thanks everyone for you suggestions and tips Now for polishing...I cant find a brass bolt big enough anywhere. This is a .50 caliber. found some that would be great for a .30 caliber rifle...just not big enough for the .50
Well, I DON'T really WANT to say it's OK.....because the possibility of screwing up your new crown is MUCH greater with a steel bolt. But, if you must, you can use a steel (round head) bolt. Brass is MUCH better for this, because it won't screw up your work by abrading the rough crown (steel on steel is not desirable). The contour of the bolt head should closely match the rough crown you've created. Make sure to use PLENTY of fine grinding paste - stop and wipe off the dirty paste and add fresh paste OFTEN. DON'T press too hard - just enough pressure to create the polishing effect - NO MORE. Let the paste do the work. Finally, make sure that the bolt head is smooth - NO raised markings whatsoever. A screwdriver slot doesn't matter (it actually helps to hold the grinding paste)....but, of course, you likely won't have that with a bolt large enough to do a 50 cal. barrel, anyway.
GO SLOW and LIGHT pressure (especially if you resort to a steel bolt) !!!
GO SLOW and LIGHT pressure (especially if you resort to a steel bolt) !!!
Sorry I didn't see this sooner. I've used a ball method for years. The only problem with it for a muzzle loader is it leaves the edges of the crown so sharp the cut out patches that enter from the muzzle and have to be shot enough times to slightly dull that edge before the cutting stop. But once you have a square cut end it works very well. I've written it up and posted it here before. I'll dig out a link.
I've seen the round head bolt method suggested for years, but one day I took a circle template to the hardware and by pressing the heads into the circles discovered all I could find were actually elliptical. You want a spherical section so it's angle of attack on the edges of the crown is the same even when you don't have the shaft you are turning perfectly coaxial with the bore. An ellipse will not be cutting evenly all around if you do that.
M. L. McPherson is the one who first put the marble idea into print, AFAIK. You use it with lapping compound and just go progressively finer until you are polishing. That's how my method works except I use ball bearings to be able to select what I want for the crown angle. I also use a cutoff wheel on a Dremel tool to groove the face of the ball bearing to hold abrasive better (standard thing to do to a lap), though you could skip that if you are willing to have it go a bit more slowly. I do the lapping with a back and forth motion, like valve grinding. Turning in just one direction usually leaves marks, while back and forth leaves a mirror smooth surface if you want to take it that far.
My method is in PDF format, here.
I've seen the round head bolt method suggested for years, but one day I took a circle template to the hardware and by pressing the heads into the circles discovered all I could find were actually elliptical. You want a spherical section so it's angle of attack on the edges of the crown is the same even when you don't have the shaft you are turning perfectly coaxial with the bore. An ellipse will not be cutting evenly all around if you do that.
M. L. McPherson is the one who first put the marble idea into print, AFAIK. You use it with lapping compound and just go progressively finer until you are polishing. That's how my method works except I use ball bearings to be able to select what I want for the crown angle. I also use a cutoff wheel on a Dremel tool to groove the face of the ball bearing to hold abrasive better (standard thing to do to a lap), though you could skip that if you are willing to have it go a bit more slowly. I do the lapping with a back and forth motion, like valve grinding. Turning in just one direction usually leaves marks, while back and forth leaves a mirror smooth surface if you want to take it that far.
My method is in PDF format, here.
