Larger lathe barrel work questions..

M

Moldmaker

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I have a larger lathe(Nardini 1640) and the head stock it a bit long for building an outboard support.

I'm looking for some input from guys here that have already invented this wheel.

I plan on putting on a 6 jaw Buck chuck, but want to know a few things that you guys are doing.

1) I normally work on tapered barrels(Tactical rifles). For barrel threading, I was thinking of making a sleeve out of Alum, tapered to the barrel contour, and then slotting it so the chuck will clamp the barrel tight when mounting.(Will need to remove action for this). The only issue is if the outside of the tube is not concentric, it could offset the thread. we put suppressors on so the barrel needs to be pretty close to the bore alignment. Input on this?

2)Cambering with a long lathe headstock. Im concerned the same issue as above, if chucking up on the chamber end, I have no real good way to adjust the barrel if it is out of line too much.


Any input is appreciated..just looking to save some headache and barrel blanks,lol..:)
 
Doing anything is a steady rest will follow the outside contour of the barrel, and have the same trouble..Maybe a bit more explanation to clarify?..;)

Thanks
 
These are some of my ideas that have worked for me. I am not a gunsmith, but a home hobbyist. I can’t say they would be ideal for chambering, but for barrel threading they work for me. Remember, Bushmaster guarantees that their barrels are concentric to within .005 of the bore. Mine are less than .001 at the muzzle and continue out to 1.5 inches checked along a pin gauge.

I have been reluctant to post them here because the guys here are the best of the best, but here goes.

The first photo shows a 22.5inch AR15 barrel that I made an extension and alignment rod for. There is also an aluminum bushing that has a 1 inch hole for pre-alignment of the barrel, until it is captured by the spider bolts. The aluminum alignment bushing works so well, I usually just leave it in place (Duct Tape so it doesn’t fall out) the barrel extension is held by the spider bolts. There is NO slop in the alignment rod or bushing.

This barrel was threaded with one half of one thousandth run out. (.0005) Pin gages are used to indicate the bore, and the alignment remained true the length of the pin gage.
ARSetup.jpg


I have made a short “Cat Head” and a “Long Cat Head” for holding pistols and rifle barrels.

I will say that the short Cat Head for real short barrels and pistol barrels works great.

This is my short Cat Head that I use to do short barrels. I also have a pre alignment rod that I can use to get the muzzle closely centered.
ShortCatHead.jpg


This is the set up for a 10/22 barrel that is cut and threaded to 16 inches. I know that this setup will receive a lot of criticism, and I myself was skeptical of it until I tried. It works great. I can indicate a muzzle to less than a half a thousandth of an inch, and the alignment stays constant the entire length of the gage pin. There is no adjustment at the chamber end, but this setup is definitely working.

The aluminum alignment bar is inserted into the headstock. It has a 3/8” hole that is 4 inches deep that captures the chamber end of the barrel. I am going to switch to half inch brass stock the next time I order, but I had 3/8” on hand. You can use different alignment rods for different barrels.

The aluminum bar was worked into the headstock a little at a time, skimming off .001 at a time until it seated deeply inside with no slop. (The aluminum bar stock was purchased at the salvage yard for $1.50 a pound.)
10-22SetUp.jpg

CloneWrench2.jpg


This is the long Cat Head. I no longer use it. It is probably 4-5 inches too long.
The long one sucks, and I will no longer use it. I just can not get anything to run true in the long one unless I spend hours tweaking it. I think it is to long, and the pipe is not true and is what causing me problems. But I will post a photo of it anyway.
LongCatHead.jpg
 
Moldmaker said:
I have a larger lathe(Nardini 1640) and the head stock it a bit long for building an outboard support.


2)Cambering with a long lathe headstock. Im concerned the same issue as above, if chucking up on the chamber end, I have no real good way to adjust the barrel if it is out of line too much.


Any input is appreciated..just looking to save some headache and barrel blanks,lol..:)
Click to expand...
A friend of mine has a larger Nardini and uses a bushing on the end of the barrel that fits in the spindle shaft bore. I'm not sure just how he starts out though. He does turn the barrel OD concentric to the ID some way.

Having a lathe that the barrel can be done "through" the spindle does simplify things a bunch.

Jackie Schmidt uses a spindle bushing method so he can explain a way that will work since his Pratt&Whitney is longer than a benchrest barrel.

http://www.benchrest.com/forums/showthread.php?t=59097&highlight=Pratt
 
I can tell you I won't be volunteering to install a threaded brake on a factory 700 barrel again. Bent barrel, non concentric and a factory finish I can't match. I used the Grizzly rod method of dialing in hoping the bullet would be traveling in that direction when it exited the banana, er... I mean barrel. No need to remove the barrel.

You may be able to go through your headstock. A cathead can hold the rear of the action while you dial in the muzzle with a Grizzly rod. It may look a little unorthodox but as long the the muzzle end is running true for a few inches your golden. I can't in good conscience advise to redial in the muzzle to its non-concentric OD so as to blend the attachment OD, but it would work on some applications such as a threaded on stainless brake.
 
Moldmaker,
I assumed that you would first turn a short section between centers before putting it in the steady. I need to study the pics above. Looks like a lot of thought was put into his method.
Butch
 
Moldmaker

Click on the link that Jerry posted, it tells you exactly how to do a barrel in a lathe that has a long headstock............jackie
 
Hi Jackie. So it looks like you thread the muzzle end for a tuning device, then screw on a ring that slips into the headstock. IF that is correct, how much clearance is between the bore of the headstock and the ring?..

do you ever have problems with the bore needing to be adjusted this way(I mean indicating a pin in the bore zero, then moving 2" out and having run-out). OR is it a non issue?. I'm just trying to cover all bases. How much runout is allowable for the bore(assume zero in one location, then moving a couple inches and take another reading).

Thanks for everyones input..Still going thru it ..
 
Moldmaker,

This is how I dealt with the long headstock problem. I don't know that it's the ideal, but it works.

Justin
 

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short barrels

I made a bushing that the barrel threads into and fits the ID of the spindle perfectly. If the threads are aligned with the bore then this method is very accurate. And I held the muzzle end with my 4 jaw and dialed it to the bore.
Jonathan
 
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