Crown Questions

[Siringo]

Someone should do a test on this - if not already done. A round ball is not affected much by less than perfect muzzles. However a conical is.

 

[M. De Land]

Someone should do a test on this - if not already done. A round ball is not affected much by less than perfect muzzles. However a conical is.

I've not tested that but it's probably true that a round ball is at least less effected by an imperfect crown than a conical with a square base. No one would purposely ding up or cut an un-square crown knowing how important it is to accuracy via patch integrity.
It must have had some effect as freshing out barrels was very common in the old days and that was most certainly primarily from loading rod muzzle wear as well as improper cleaning.
I wonder if false muzzles were first or ever used with patch ball rifles ?
I would also like to test muzzle coning at some time to see if it is as accurate as square crowning. I have a friend with a coned crown and he says he couldn't tell any difference before and after but it was not on a bench gun but rather his offhand rifle.

 

[IanH]

Outstanding description of the barrel maker's and gunsmith's challenges. I was poking a little fun at your "perfectly square with a file" remark but the truth is it's been done that way for centuries and it works just fine if done with a little care.

As to coning, my limited experience with two rifles that had good crowns and shot very well before coning shot equally well after coning at both 50 and 100 yards. This is with a two minute of angle resolution/sighting error, best I can achieve. There may be discernible error introduced or eliminated by muzzle coning but such errors are smaller than my particular shooting ability with notch-and-blade barrel sights.

My method of coning is approximately 8-10 thousandths per 1.5", per side, strictly to facilitate field loading with the under barrel rammer.

 

[Siringo]

I've not tested that but it's probably true that a round ball is at least less effected by an imperfect crown than a conical with a square base. No one would purposely ding up or cut an un-square crown knowing how important it is to accuracy via patch integrity.
It must have had some effect as freshing out barrels was very common in the old days and that was most certainly primarily from loading rod muzzle wear as well as improper cleaning.
I wonder if false muzzles were first or ever used with patch ball rifles ?
I would also like to test muzzle coning at some time to see if it is as accurate as square crowning. I have a friend with a coned crown and he says he couldn't tell any difference before and after but it was not on a bench gun but rather his offhand rifle.

All my rifles are crowned. I developed the load before crowning. After crowning I could detect no difference.

 

[M. De Land]

All my rifles are crowned. I developed the load before crowning. After crowning I could detect no difference.

Do you mean "coned" as well as crowned or do you mean only crowned ? There two different procedures.

 

[Uncle Miltie]

F.W. Mann's book The Bullets Flight details his extensive experiments with damaged muzzles and how they affect accuracy at the target.

 

[Ed C.]

That is the theoretical method of barrel centering work but the reality is that no bore is ever perfectly straight nor has a perfect zero in run out. These are two entirely different things as is bore diameter uniformity. Good barrels will be with in .0004 in this regard unless hand lapped closer. You can feel a ten thousands or two when hand lapping with poured and charged lead slugs. Best grade match barrels are not mechanically straightened either they are bored as straight as possible or rejected. If one can get under .004-.005 run out in 30 inches that is about as straight as it gets from what I have read.
Also a barrel plug gauge has to have a few tenths of clearance to fit into a bore and the bore must be even for a meaningful dial indication on the gauge for a center.
I have to do all the turning, threading , crowning and chambering between centers in a steady rest in my lathe as the head stock hole is not large enough but it is just as accurate if not more so when accomplished correctly.
One can dial indicate both ends of a barrel and adjust as close as the run out will allow then turn the lathe on in slow rotation while looking down the bore that can look like a jump rope inside and yet be straight on the outside with the end holes on as close center as possible.
Deep hole boring is an art form and is the heart of any super accurate barrel as everything from there on out is based on and depends on how even and straight it was bored. This will effect reaming and what ever form of rifling method that is used.

And after all this highly technical and exacting stuff is done, that gun will only shoot as good as the human pulling the trigger. How perfect does a gun need to be in the real world?

 

[M. De Land]

And after all this highly technical and exacting stuff is done, that gun will only shoot as good as the human pulling the trigger. How perfect does a gun need to be in the real world?

That is exactly true buttttttttttttttttttttt the more error one can remove from the gun the less total error there is for the marksmen to be negatively influenced by and the greater the odds for higher score.
The more accurate the target arm the greater the probability of hitting the desired mark. This is a constant regardless of the marksmens skill level.

 

[Siringo]

Do you mean "coned" as well as crowned or do you mean only crowned ? There two different procedures.

Dang spell check. Yes coned!

 

[Sooty Scot]

And after all this highly technical and exacting stuff is done, that gun will only shoot as good as the human pulling the trigger. How perfect does a gun need to be in the real world?

Only good enough to compensate for the failing nut behind the trigger.

 

[Nav]

Does anyone cut a 30 deg target crown on their barrel, or is that just too period incorrect? A “flat” crown plain sucks for a rifle, and I completely agree that it is just about the most important part of the barrel. I’ve turned some dogs into tack drivers just by giving them over to my gunsmith to rework the crown.

 

[necchi]

Your right, a proper crown is important,, I'm not sure what degree it should be,, (?)
A big marble works good with wet/dry sandpaper,, even a thumb if ya spin the barrel.
From what I learned the crown just has to be the same,, all around the muzzle.
What is the tool a lathe uses? A Ball Mill end?
If you have some science about a proper degree, please share, Honest,
I'm sure Bobby Hoyt knows, .
p.s. Don't forget about the whole "conning" the muzzle thing,, that debate's been going on for the 14yrs I've been here,,

 

[SDSmlf]

Some folks like to use their thumb over fine grit wet sandpaper to polish a crown, and it seems to work.

Personally, I like to cut a 60° chamfer with a lathe, then polish. Belts and suspenders approach proven to work. Without or without a lathe, I would have used the ball bearing process I have posted about here a number of times.

Using a series of ball bearings (guess you could use glass balls or marbles), from about one and half times the bore diameter, to right around bore diameter, and using sandpaper of different grits from 120/180 up to 320 or finer (I take it up to 1000 grit
if I want a mirror finish, think working on someone else's gun). A couple of turns of the muzzle over each ball bearing with progressively finer sandpaper over them gives a smooth barrel crown to bore transition.

Basic idea is to hold the sandpaper over the ball bearing (you can place ball on the floor and hold paper with your feet, maybe on a pad or thin carpet if you don’t have a lathe to chuck up the barrel in) and rotate the barrel bore on the bearing with the sandpaper on it. Easy to keep barrel square with the floor. I’ll start with the larger diameter bearing and roughest grit paper and end with a smaller ball bearing near bore diameter, repeating with progressively finer grit sandpaper. I stop when I have a slight chamfer on bore and rifling lands that is highly polished.

I use Dykem (or a Sharpie) to mark the inside the bore so I can easily see when I starting to clean up everything without going too far. Note the 60° chamfer in the photograph was cut on a lathe, I just use the ball bearings to break up the lumps and sharp edges and polish the crown.

Note that with any method involving sandpaper, and your barrel is already finished, you are going to remove finish from the face of the bore if you don’t protect it. I’ve used ‘masking’ tape with a hole punched through it (use a wad punch), but only on other people’s gun’s, not worrying about the finish on mine.

 

[IanH]

Proper coning doesn't impair consistency.

I prefer a radiused crown, no sharp edge, high polish. Grind a tool and use a tenths indicator to run the barrel perfectly true:

This one was coned with a tiny boring bar and counterbored on the lathe, the crown itself is a radius but not fully blended with the muzzle face:

This one isn't radiused but is deeply coned to thumb-start a very tight patch/ball and send it down with only the 5/16" underbarrel rammer. I turned a piloted mandrel on the lathe, slit the tapered portion, and wrapped it with sandpaper:

 

[SDSmlf]

Proper coning doesn't impair consistency.

I prefer a radiused crown, no sharp edge, high polish. Grind a tool and use a tenths indicator to run the barrel perfectly true:

View attachment 241865


View attachment 241866

View attachment 241870

This one was coned with a tiny boring bar and counterbored on the lathe, the crown itself is a radius but not fully blended with the muzzle face:

View attachment 241867

This one isn't radiused but is deeply coned to thumb-start a very tight patch/ball and send it down with only the 5/16" underbarrel rammer. I turned a piloted mandrel on the lathe, slit the tapered portion, and wrapped it with sandpaper:

View attachment 241869

Most folks here don’t have access to a lathe or know how to use it, let alone know what a boring bar is.

What do you suggest for those without a precision lathe?

 

[IanH]

I was more or less responding to Necchi about what tool would be used with a lathe to radius the crown. Extreme long-range unmentionable gunsmiths have experimented with crown angles from zero to 45⁰ and found it makes no difference so long as it is concentric and perfectly perpendicular to the bore axis.

If you don't have a lathe, use the radiused shoulder of a straight machinists punch and sandpaper. Build up a bore-sized bushing on the end of the punch with masking tape.

 

[necchi]

Extreme long-range unmentionable gunsmiths have experimented with crown angles from zero to 45⁰ and found it makes no difference so long as it is concentric and perfectly perpendicular to the bore axis.

Thank you. While it's difficult for most folks without machine tools to achieve "perfect", having concentric form is the key.
And for these things, common tools used with a little research and diligence can go a long way to improving accuracy within common range.
Those that seek long range can and do achieve. There is shared knowledge here about high performance. But those that do have used modern measurement tools, machines and very selective techniques to get there.

This stuff isn't about a feller that has a ding on one the side of his Traditions Kentucky that was left there by Uncle Jeff when he borrowed it for squirrel hunting.

 

[Sooty Scot]

Proper coning doesn't impair consistency.

I prefer a radiused crown, no sharp edge, high polish. Grind a tool and use a tenths indicator to run the barrel perfectly true:

View attachment 241865


View attachment 241866

View attachment 241870

This one was coned with a tiny boring bar and counterbored on the lathe, the crown itself is a radius but not fully blended with the muzzle face:

View attachment 241867

This one isn't radiused but is deeply coned to thumb-start a very tight patch/ball and send it down with only the 5/16" underbarrel rammer. I turned a piloted mandrel on the lathe, slit the tapered portion, and wrapped it with sandpaper:

View attachment 241869

I have never before seen that sort of exterior muzzle treatment. I like it.
I'll bet it makes quickly centering a ball board easier.

 

[M. De Land]

That is the theoretical method of barrel centering work but the reality is that no bore is ever perfectly straight nor has a perfect zero in run out. These are two entirely different things as is bore diameter uniformity. Good barrels will be with in .0004 in this regard unless hand lapped closer. You can feel a ten thousands or two when hand lapping with poured and charged lead slugs. Best grade match barrels are not mechanically straightened either they are bored as straight as possible or rejected. If one can get under .004-.005 run out in 30 inches that is about as straight as it gets from what I have read.
Also a barrel plug gauge has to have a few tenths of clearance to fit into a bore and the bore must be even for a meaningful dial indication on the gauge for a center.
I have to do all the turning, threading , crowning and chambering between centers in a steady rest in my lathe as the head stock hole is not large enough but it is just as accurate if not more so when accomplished correctly.
One can dial indicate both ends of a barrel and adjust as close as the run out will allow then turn the lathe on in slow rotation while looking down the bore that can look like a jump rope inside and yet be straight on the outside with the end holes on as close center as possible.
Deep hole boring is an art form and is the heart of any super accurate barrel as everything from there on out is based on and depends on how even and straight it was bored. This will effect reaming and what ever form of rifling method that is used.

Probably the most accurate crown that can be made is cut with a properly fitting down bore spud, hand driven muzzle cutting tool. This is because the down bore spud orientates the most accurate square to the bore axis cut possible.
I always use my lathe with a spider in a steady rest for octagon or round barrels but even this is not as accurate as the spud squared , hand cutter tool ,specifically designed for crown cutting . This tool orientates the muzzle cut to the actual bore run out of the specific barrel.

 

[Grenadier1758]

Most folks here don’t have access to a lathe or know how to use it, let alone know what a boring bar is.

What do you suggest for those without a precision lathe?

Since most shop lathes aren't large enough to properly turn a rifle barrel, I recommend the thumb and metal working sandpaper method to smooth the sharp corners at the muzzle. A ball wrapped in sandpaper will keep the crown even. It doesn't take much smoothing to provide a good crown. I have one rifle with a crown that looks like the fine edge of @SDSmlf's rifle. A deeper crown will make loading easier as it is almost a cone and also protect that transition from rifled barrel to free air. Making loading easier is justification enough for a good smooth crown. Preventing the cutting of patches and maintaining accuracy on target makes getting a good crown mandatory.