Home Forums Hunting & Shooting Gunsmithing Muzzle Threading

I want to thread the muzzle on my son's H&R 17 HMR barrel for a suppressor. The spindle bore of my lathe is too small to fit neither the lug end of the barrel in it nor will the forend stud fit through. I have considered threading it between centers with a small aluminum plug fitted for the bore that gives enough offset from my live center to cut threads all the way to the end. But...how do I indicate from the bore? I don't trust the outside of the barrel is concentric nor do I trust that the bore was cut perfectly center.

Any advice is appreciated.

Where would that go? My live center has to rest on the bore plug to hold the barrel.

You wanted to center everything up on the bore right?

Yes but I'm not sure how to do that without the live center supporting the end of the barrel. My barrel won't fit inside the spindle bore.

Maybe you could get a 1/2x28 die and somehow make a fixture to allow it to be dead ass straight with the bore. I can picture what would need to be done but I struggle to find the words to describe what would work.

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We need some Smyth Busting here...

One way or another, I'm using my lathe. I'm fairly certain the lathe can be used to start a die straight much like using a mill to keep a die straight, but I would prefer to not use a die.

Do you have a way to center up the die with the tailstock? Square it up with the barrel?

The die?

Use a brass "crown saver" from Brownells on the live center. Swing the barrel between centers on your lathe. Cut the muzzle end to 1/2". Because you are between centers, the cut will be concentric with the bore. Thread in the usual way. I often run a die over the completed threads to smooth them up.

Why not put it in a steady rest, then check with a dial indicator off of a brass rod in the bore to see if it's concentric. Thread as usual if it's good.

That may work. I have a steady rest but I hate using it on a finished barrel for a few reasons. One, it's been a bear to indicate a barrel in perfectly round. Two, the brass contacts have left marks on the barrel. Tonight I have learned a few ways to improve upon both of those issues and it's time to try again using better techinques.

My old lathe only has a 1" bore headstock. I know your pain.LOL

Maybe put one of THESE in the tailstock.

I'll get one. I can see using it on something.

I make a nylon plug to protect the crown. Either that, or true up the crown after threading. GD

You have to cut a shoulder first, then thread it while indicating on the bore centerline.
You don't want to trash your suppressor because of Bubba-ed muzzle threads.

I always thread with the live center, after making my major diameter cut for threading to length. The crown is the least of my worries as It gets easily touched up with a brass ball or slotted round head wood screw with VG compound on it, but if done properly , the live center doesn't hurt the crown , as my live center is softer than the barrel. Centering the chamber in the headstock can be a challenge depending on the barrel , sometimes that takes a solid center and a lathe dog clamp to get that , or a machined "chamber rod" sized to allow a barrel with a rear welded mount to ride between jaws and a small hard wood wedge to keep out any backlash. I have used my steady rest WITHOUT contact 1/4 of the way back from the muzzle, then to check threads or run a die, run the rest contacts up to the barrel for support, back the tailstock off to check, reinsert tailstock , lower the steady rest contacts and continue as necessary. You wont mar the barrel finish this way.
Rich

I use a half dead center. Gives enough room to do it. Centers on your bore.