Barrel Crown

Heavy sits the crown on the king's head

Here is a trick that Ralph Stewart taught me that works very well. I cut a 90 degree crown from the inside out with a carbide tool. Before cutting and after indicating the muzzle pound a 6mm bullet point first into the bore a little ways gently with a small hammer. cut the crown making sure you cut into the bullet jacket initially. Pull the bullet out with pliers or push it out with a blunted cleaning rod. The crown should be sharp with no burr. If you are left with a circumferential burr outside the bore you did not cut into the bullet enough. Tim
 
Tim Oltersdorf said:
Here is a trick that Ralph Stewart taught me that works very well. I cut a 90 degree crown from the inside out with a carbide tool. Before cutting and after indicating the muzzle pound a 6mm bullet point first into the bore a little ways gently with a small hammer. cut the crown making sure you cut into the bullet jacket initially. Pull the bullet out with pliers or push it out with a blunted cleaning rod.. Tim
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Dr Tim, I have studied on this off and on for a day or so. How U gonna' get hold of that bullet with pliers? Are you leaving the bullet sticking out and just plunging the tool into it a short ways?

Ralph Stewart?? Didn't he get run out of Texas by a posse for something? We have a guy moved into Tennessee a few weeks ago that is a Stewart but his name is Trabon Stewart??? Kin you rekkon??
 
If you looked a a much magnified view of most sharp crowns, even ones cut with a good sharp tool, here is what you are up against;




dfy3hv.jpg




And if one of those tiny burrs break off instead of getting pushed away you might just have a crown that can greatly hurt accuracy.

BTW, this photo is from a series of pictures Greg Walley took of a bunch of different crowns in different barrel steels by several different benchrest gunsmiths. According to Greg it was very interesting as to the end result various gunsmiths accepted as good to go.

Bottom line, the last part of the barrel the bullet sees is very important as to how its flight begins.
 
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Jerry
In your opinion will the bullet act as a lap over the course of a dozen shots? It would be interesting to see before and after close up as you posted above. Perhaps the little nicks and voids fill with carbon and copper??? Lee
 
skeetlee said:
Jerry
In your opinion will the bullet act as a lap over the course of a dozen shots? It would be interesting to see before and after close up as you posted above. Perhaps the little nicks and voids fill with carbon and copper??? Lee
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I wouldn't depend on the fired bullets solving the problem of burrs on the crown face. When Frank Green was still at Krieger he sent me some videos, highly magnified, showing what the crown edge looks like when the barrel owner tried to shoot burrs out.

Probably the best solution I have found is a micro-bevel. I indicate the muzzles grooves, with a 0.0001" Interapid indicator, till I can't see any movement at all. Then I take a really sharp, really positive rake, tool and cut a 45 degree bevel, cutting the lands down to just slightly past the grooves. About a 0.005" x 45 surface.
 
That pic looks like one of the ones Greg Walley took a few yrs back..... interestingly enough the toolmarks don't seem to be from a lathe so much as from a cutoff tool.

??

al
 
That pic looks like one of the ones Greg Walley took a few yrs back..... interestingly enough the toolmarks don't seem to be from a lathe so much as from a cutoff tool.

??

al
 
The micro-bevel,IMO, does a more predictable job of ending up with a perfectly symmetric exit for the bullet than does using a ball bearing or screw head as lapps to break the sharp edge.
 
alinwa said:
That pic looks like one of the ones Greg Walley took a few yrs back..... interestingly enough the toolmarks don't seem to be from a lathe so much as from a cutoff tool.

??

al
Click to expand...

I thought the same. The tool marks do not run parallel to the bore. Brian.
 
alinwa said:
That pic looks like one of the ones Greg Walley took a few yrs back..... interestingly enough the toolmarks don't seem to be from a lathe so much as from a cutoff tool.

??

al
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Actually, that particular photo is of a section of a benchrest grade barrel that was sawed off. The edge in the lower left is the band-saw cut edge. I was trying to focus the image on the rifling land/groove area.

I have some other photos of the actual crown edge. I'll have to dig those up when I find them and repost.

Unfortunately, I only have a small fraction of the photos that I took of the samples. I had hundreds on a ZIP drive disk that I've misplaced. I hope I can locate that disk someday.

Greg Walley
Kelbly's Inc.
 
skeetlee said:
jerry
i wish i had a grinder or the knowledge to grind my own tools. If you will remember Jerry you made me a crowning tool a few years back. that tool worked great but unfortunatly the 1/4" tool wont work on my big grizzly. i wish i had one in 1/2", hint hint!!! lol. thanks jerry. lee
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Golly I cannot imagine a person who has a lathe and no pedestal grinder :).

Hand grinding things is a skill worth learning.

For some tools in shops where one was avail I actually liked to use a belt sander that had a well broken in belt on it, it offers you a lot more flat surface to work on than a grinding wheel does, hand grinding say a 2" drill is one example where a belt or disc sander rocks.....even if you are just ripping off some damage before putting the drill into a drill grinder.

Bill
 
Al
That misting unit looks very useful. How would you hook it up though? Does it hook directly into my coolant pump on my lathe? What type or brand of coolant do you use in yours?

I now also has a ped grinder in my shop what type of wheel should I purchase for grinding hss?

Here is something else I will share while I'm here. Just as a curiosity test I took a ppc that was shooting a flat .250agg here at home at 100 and decided I would see how important dialing in the muzzle to crown really was. I took that barrel in chucked it up in my 3jaw and then faced and crowned. No indicating what so ever. When I was done the barrel still shot a .250 . Not sure this little test showed me anything really as I always indicate my barrels, as I did this barrel when I was done with my test. The barrel did shoot though.

Something else a little more serious that I tried this past week was to sand a finish on a flat crow. I took a flat square piece of steel and rapped 320 onto the face. I then pressed the flat steel with sandpaper against the crown while the barrel turned in the lathe. The finish looked very good under my loop and no burrs. The barrel shot very well also. Lee
 
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skeetlee said:
Al
That misting unit looks very useful. How would you hook it up though? You power it with your air compressor, it works like an engine cleaner or a sandblaster. It comes with a slender pickup hose, maybe 1/8"id clear plastic tubing. I stuff that into a gallon milk jug of water.Does it hook directly into my coolant pump on my lathe? Nope, much more easierWhat type or brand of coolant do you use in yours? water

I now also has a ped grinder in my shop what type of wheel should I purchase for grinding hss? Carborundum, I gener'ly just buy "cheap" ....... altho I've got wheels marked and sold as "aluminum oxide" and "silicon carbide" I don't know the difference, if there is one. You need a coarse on one side (36-60 grit) and a fine on the other and you need to fabricate a stout support rod or plate of some kind
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answers in bold



I spent several years experimenting, wasted countless hours grinding bits. I got to the point I'd keep 10 bits in a tray of water and rotate thru them a few seconds at a time trying to not burn the edges but it's heartbreaking to get juuuust to the end and BOOM! a nice blue edge....

I tried a water drip
I tried air
I tried the belt sander
the drum sander
the plate sander
I bought a 500.00 tool grinder with water feed to the inside of the wheels
I used buckets of ice cubes
I built a spring-loaded feed table with a water dripper so's I could walk away and let it grind for hours
I built a low-speed grinder with a huge wheel
I built a gravity rocker unit to let the tool bit ride with light consistent pressure
I was near to buying a surface grinder just for grinding toolbits when I bought the misting unit.


Ba-da-BOOM, problem solved.

al
 
Why water and not some type of cutting fluid?
No oil because you take a chance on breathing the oil mist?
Interesting, I think I'll order one this week along with a couple more tool holders. Lee
 
skeetlee said:
Why water and not some type of cutting fluid?
No oil because you take a chance on breathing the oil mist?
Interesting, I think I'll order one this week along with a couple more tool holders. Lee
Click to expand...

#1 because water's free
#2 because it's a portable unit, I use it on 4 different mo'chines
#3 because it sprays on the floor.....and on your arm and stuff :) water just evaporates
 
I chambered a couple barrels this weekend of two different makers. One barrel crowned up real nice. The other not so much. Long story short. I tried all my normal tools with not much luck. I wasn't happy anyway. I kept looking and noticing how sharp my kennametal threading tool looked. I tried it and it worked awesome. Perfect in fact. Barrel shoots lights out. Interesting I thought. Lee
 
The best tool for any job

is the one that works best, eh? All too often we box ourselves into what we should use vs what works. Of course, there is always the mother of invention lurking.

Pete
 
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