Barrel shortening & crowning

[wet willy]

I'd welcome ideas on shortening and crowning a barrel.

I have an Atlas 42" lathe, but sadly the headstock is limited to 7/8" material so I can't run any rifle sized barrel through it. I have a 4-jaw chuck and live centers.

Made a brass mandrel bore size with a slight taper, held it in place with a live center, used a cut-off tool to remove the excess barrel, then a curved cutting tool to make the crown, all the time sacrificing the mandrel. That worked OK if I didn't cut too much crown. Scheme works but a lot of work for what it did, plus the last few very shallow crowning cuts into the mandrel produced chattering.

Other than hand cutting and filing/T-square route, does the Forum have suggestion on how to utilize my shop equipment to shorten and crown a barrel?

[J.D.]

Just use Crisco for patch lube and bore preservative. It is shortening, after all. 

Sorry, I couldn't help myself...Ok, so I could, but didn't. 

I just trued up the muzzle of an old Douglas barrel using the file and square. The crown/slight cone was applied using a cone shaped grinding stone for a dremmel tool.  The stone was held stationary, by hand, and the barrel rotated, by hand, with the unbreeched breech end of the barrel placed on a piece of board, to get a concentric crown/taper.

Using your lathe, a tool similar to a counter bore can be made to square the muzzle. If the cutting end of the counter bore is large enough, it can be used, with removable pilots, to square the muzzle of nearly any diameter barrel.

There is a tutorial on making a crown tool in the tutorial section, but I prefer to do it the quick and easy way.

God bless

[northmn]

I could probably have a barrel shortened with a hacksaw, square and file almost as fast as set up time on the lathe.  They always shot well afterward.  If your lathe is not quite large enough you may end up doing the hand work anyway.  I have a tapered barrel in a 54 that had one flat slightly off from being done on a milling machine that may not have been set up for the job.  The off flat is on the bottom and I really do not care, but am pointing it out.  While I do envy those with a machine shop, I have done quite a few tasks with hand tools.  Part of the game.

DP

[Don Getz]

Even if you have a four jaw chuck, you can't merely chuck the barrel up in it and let the remaining barrel protrude thru the
headstock, and then spin the barrel.    Too much overhang, will wobble like crazy.  Here's how I would do it.   First, screw
a piece of round stock that is threaded into the breech, hold this in the chuck. You could chop of the barrel fairly close to
where you want the actual length to be.   Then insert a brass plug into the bore with a center detent in it....hold that in
the center in the tail stock.    I then take a cut-off tool and cut the barrel at the proper spot, but NOT all the way off....cut
it down until there is a little bit of barrel left to remove.   I will then saw off the remaining barrel at the bottom of the cut-
off spot, then file off this small area.  Since you have already cut if off with the cutoff tool, you have a nice square muzzle,
except for that small remaining area that you sawed off.  It is easy to get this filed off even with the rest of the muzzle.
I would then use a large countersink with a brace and bit to cut a crown on the barrel.   You could polish it like Taylor says
with some fine emery paper and you'll have a good crown...................Don

[Dphariss]

I'd welcome ideas on shortening and crowning a barrel.

I have an Atlas 42" lathe, but sadly the headstock is limited to 7/8" material so I can't run any rifle sized barrel through it. I have a 4-jaw chuck and live centers.

Made a brass mandrel bore size with a slight taper, held it in place with a live center, used a cut-off tool to remove the excess barrel, then a curved cutting tool to make the crown, all the time sacrificing the mandrel. That worked OK if I didn't cut too much crown. Scheme works but a lot of work for what it did, plus the last few very shallow crowning cuts into the mandrel produced chattering.

Other than hand cutting and filing/T-square route, does the Forum have suggestion on how to utilize my shop equipment to shorten and crown a barrel?

Make one of these.


Use double stick carpet tape, the thinnest you can find to attach 320-400 grin wet or dry. I turn it with an electric drill using low pressure. Too much pressure may wad the tape up.
You can make one of these to cut any crown angle you want. Polish with 600 grit.
I would make one with a sharper angle relative to the bore as a rougher than use one similar to this to make a 2 angle job it will load easier. Do not use the longer taper to take too much off the lands. Just enough to change the angle a little.

A single angle job like this will work fine as well.

I don't recommend deep funneling.

I have a decent photo of a crown I just did on a 58 but its on the other computer and not on photobucket.

Dan

[Daryl]

Here's my favourite crown shape, started like Dan's using emery wrapped around a tapered stone in the electric drill, then finished with my thumb and emery rotating the barrel every now and then.  About 15 min 'work'.

[Dphariss]

This is a photo of a 58 caliber GM barrel after the proof load.
Heavily fouled but it shows the crown very well, its a "2 angle" as the photo shows.
I am waiting for the owner to get back to me on how it shoots after load development.
For some reason this bore size fouled like crazy with anything more than 90-100 grains of Swiss.
90 grains shows no fouling at all at the muzzle, 110 looks about as bad as this (220 gr of powder and 2 balls).
Mad Monk says its a critical temperature thing effecting the fouling.
Dan