Bad threading job

D

Dennis Sorensen

Guest
I just removed this custom barrel from a 700 Remington. Chambered in 7mm STW the chamber was way oversize... measuring .529" in front of the belt.

The tops of the threads felt tight in the action... the "goop" is some kind of Loctite...

I haven't seen one this bad for a long time. What a mess!

screwedupbarrelthreads-0.jpg
 
Split threads. Must be some trick switch barrel!!

Must have learned how to thread and chamber from Benchrest Central.

Dennis, what do the action threads look like?
 
Funny, tonight I was looking at a factory rem barrel I had taken off a couple years ago. The threads look almost identical. Couldn't believe the hack job on it.
What are you replacing it with Dennis?
 
I don't know what make this barrel is or who installed it. The action threads are unaltered and undamaged factory.

If this chamber had not been so much oversize in diameter it probably would not have been brought to me...

I have just screwed a customer supplied .300 Win Mag factory 700 barrel in place... a pull off just like new.
 
On another forum people regularly ask "I want to be a gunsmith where do I start?" Unfortunately I have seen too many threading jobs like the one in the pic so that is what I am reminded of when that question is asked.

I am enough of a novice that I still get the textbook out and review everything before I get started.
 
Dennis Sorensen said:
I just removed this custom barrel from a 700 Remington. Chambered in 7mm STW the chamber was way oversize... measuring .529" in front of the belt.

The tops of the threads felt tight in the action... the "goop" is some kind of Loctite...

I haven't seen one this bad for a long time. What a mess!
Click to expand...


Looks more like a gunowner requested a gunsmith or re-chambered/threaded the barrel on his own, from a previous cartridge/action.........looking at the various relief steps and possible varying thread angles...........Don
 
That almost looks like setting the compound to 30 degrees on an import lathe that is marked 30 degrees from parallel instead of 30 degrees from the perpendicular. I cut my first practice thread when I bought a Jet lathe back along time ago. I set the compound to 30 degrees or 29 1/2 and cut the ugliest thread you ever saw. It fed in at 60 degrees instead of 30 and cut what looked more like a buttress thread than a v thread. It didn't take long to figure out that it needed another witness mark to be able to feed in at 30 degrees off the perpendicular.
 
Mike Bryant said:
That almost looks like setting the compound to 30 degrees on an import lathe that is marked 30 degrees from parallel instead of 30 degrees from the perpendicular. I cut my first practice thread when I bought a Jet lathe back along time ago. I set the compound to 30 degrees or 29 1/2 and cut the ugliest thread you ever saw. It fed in at 60 degrees instead of 30 and cut what looked more like a buttress thread than a v thread. It didn't take long to figure out that it needed another witness mark to be able to feed in at 30 degrees off the perpendicular.
Click to expand...

I run into the same problem threading with my Jet Lathe with the compound set at 30 degrees. What did you end up setting the compound at to get good threads?
 
The way all the different flats, angles and v's swap sides as you go along the threads I'll bet it was a remodeling job on a barrel from another brand of action with a different thread pitch.

God that's ugly.

Dave
 
I agree with Mike on some import lathes you have to set the compound to 59 ½ degrees to get the correct angle. Like Mike I found that to be true with the first practice cut on my Birmingham lathe. Possibly the chamber was cut using a center to guide the reamer with an out of alignment tailstock. I would like to see a picture of a fired cast from that barrel.
 
Bad threads..

There is a "Gunsmith" in my area that has no business doing any machining. I have had to tell several customers that their rifle and or barrel was ruined by this man. I have a number of customers call and ask that I rebarrel a rifle he has worked on. I have to tell them that I will have to inspect their rifle and or barrel before accepting their work. I have refused several. Just last week I had a man bring a Remington 22-250 with an aftermarket muzzle brake. You could see light between the brake and the barrel shoulder. The customer told me he had to return the rifle to the smith whom he now calls "pipe fitter" because the bullets were hitting the brake. The customer told me the "gunsmith had to order him a new brake. I removed the barrel and am not sure it had ever been removed from the action before. I then removed the brake. The hole diameter measured .314 on the rear and .317 on the front. I explained to the customer the brake hole diameter needed to be no more than .020" larger than the bullet diameter to be effective.
The general public sees the sign "gunsmith" and thinks anyone can do machine work. Most gunsmiths make a living cleaning guns and replacing parts. Anyone having a rebarrel job should check out the smiths work before committing to have machining done.

Nat Lambeth
 
Dave Tooley said:
The way all the different flats, angles and v's swap sides as you go along the threads I'll bet it was a remodeling job on a barrel from another brand of action with a different thread pitch.

God that's ugly.

Dave
Click to expand...

David, I believe you are right. (Why would I have even dared thinking you were wrong..tee hee) It looks like the barrel may have been an 18TPI and rethreaded to 16TPI. It looks like the guy also used an Acme tool to thread with.
 
Its was very easy to make pretty threads like this with my first lathe.
A single tool post was supplied. I could not stop the tool post from
rotating cw as the thread advanced.That caused the flank to shift
as the thread became deeper. I replaced the tool post with blocks
much like quick change without height adjustments to hold insert
tooling and H.S. bits. That put that problem away. Its very ridgid
and quick to change. Each block is made to hold tooling at the correct
height. The picture looks like 3rd day in high school shop class, I hope
it was tied to an old tire and fired with a long rope the first time.
 
If the barrel shank was undersized, as well as poorly threaded, might that have allowed the chamber to swell even if pressures were within limits?
 
Old Gunner said:
If the barrel shank was undersized, as well as poorly threaded, might that have allowed the chamber to swell even if pressures were within limits?
Click to expand...

Probably not. The chamber pressure would have been in the 45,000-65,000 range and the yield strength of barrel steel would be in excess of 110,000.
 
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