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How tight should the breechplug on a barrel be? 4 foot spanner tight? 12 in. crescent wrench tight? Something else tight?
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12" cresecent wrench tight. Snug. It is not the sort of thing to vibrate loose. I've seen originals i could loosen by hand, practically, but do not recommend it.
The National Assembly Torque recommends 100 ftlb on a 5/8 coarse thread grade 2 and 70 ftlb on a 9/16 coarse thread grade 2. This should be sufficient for any breechplug assembly as well.
That is a pretty hefty little hooch with a half/inch drive ratchet leingth handle.
That is a pretty hefty little hooch with a half/inch drive ratchet leingth handle.
Erzulis boat
45 Cal.
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- Jul 14, 2005
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Every breechplug installation will vary in torque values.
If indexing is required, such as an installation on an octagonal profile barrel, the location of the tang relative to a corresponding flat will dictate the required force to "sock it down".
The most critical factor involves positive contact with the face of the breechplug with the inside shoulder of the barrel. This must coincide with the index, tricky at first, but easier every time after.
Once you are positive that proper contact is achieved, it should require some force to tighten. A 4 foot breaker bar is too much, and a 4 inch Chescent (Chinese Crescent wrench) is too little. You should definitely feel it tighten up, but not so tight that you feel that the barrel might twist. You MUST have a solid bench and vise, as a rickety setup will give a false feeling of the proper torque.
To illustrate, let's say that the tang is one flat short of being aligned AND bottomed out. No way! You would have to call some Cosmonaut buddies over to tighten that one. You should only be off about two thirds from indexing after a very light snug with the wrench.
The one good thing is that because of the substantial diameter of the threaded portion of the breechplug, it will stop dead cold, and not permit you to severely over torque it. (Most breechplugs that is, some ill fitting or cast ones might disfigure or break.)
My breechplug wrench is 14 inches long, and I just roll them into place with some good force, but never to the point where I have to jerk the wrench. In actual foot pounds, the figure might run 20 to 30 pounds for a 5/8 diameter plug. a breechplug has shallow penetration, and established torque values for fasteners should not apply. They are plugs, not fasteners subjected to vibration and shear loads etc.
This is a "feel" issue, and no matter what I tell my Brother in law, He will always torque everything to the moon!
This is just my particular take on the issue.
:m2c:
If indexing is required, such as an installation on an octagonal profile barrel, the location of the tang relative to a corresponding flat will dictate the required force to "sock it down".
The most critical factor involves positive contact with the face of the breechplug with the inside shoulder of the barrel. This must coincide with the index, tricky at first, but easier every time after.
Once you are positive that proper contact is achieved, it should require some force to tighten. A 4 foot breaker bar is too much, and a 4 inch Chescent (Chinese Crescent wrench) is too little. You should definitely feel it tighten up, but not so tight that you feel that the barrel might twist. You MUST have a solid bench and vise, as a rickety setup will give a false feeling of the proper torque.
To illustrate, let's say that the tang is one flat short of being aligned AND bottomed out. No way! You would have to call some Cosmonaut buddies over to tighten that one. You should only be off about two thirds from indexing after a very light snug with the wrench.
The one good thing is that because of the substantial diameter of the threaded portion of the breechplug, it will stop dead cold, and not permit you to severely over torque it. (Most breechplugs that is, some ill fitting or cast ones might disfigure or break.)
My breechplug wrench is 14 inches long, and I just roll them into place with some good force, but never to the point where I have to jerk the wrench. In actual foot pounds, the figure might run 20 to 30 pounds for a 5/8 diameter plug. a breechplug has shallow penetration, and established torque values for fasteners should not apply. They are plugs, not fasteners subjected to vibration and shear loads etc.
This is a "feel" issue, and no matter what I tell my Brother in law, He will always torque everything to the moon!
This is just my particular take on the issue.
:m2c:
B.Habermehl
45 Cal.
- Joined
- Jul 29, 2004
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I'll have to agree at the estimated torque of about 30 to 50 foot lbs. Most of the Getz, Colerain, and Rice barrels I have worked with took about that much torque to reseat them to the index marks. My first few breeching jobs were probably a bit tighter maybe as much as 75ft lbs or so. reflecting my training by a modern custom riflebuilder (cartrige guns). The fit at the front face of the plug is by far the most important detail. Think in terms of a globe valve's plug and seat, that must be gas tight. BJH
Just a thing to keep in mind. Threads only have a certain amount of strength before they shear off.
If a person uses up that strength by running the breech plug into the end of the bore shoulder there will be no strength left to resist the 5000 to 25,000 pounds per square inch of pressure that occures when the gun is fired.
IMO, even though these large threads can take a high torque without stripping (shearing) it is a good idea to keep the torque in the 25-50 ft/lb range so the unused strength will be there to resist the high pressures of shooting. :hmm:
If a person uses up that strength by running the breech plug into the end of the bore shoulder there will be no strength left to resist the 5000 to 25,000 pounds per square inch of pressure that occures when the gun is fired.
IMO, even though these large threads can take a high torque without stripping (shearing) it is a good idea to keep the torque in the 25-50 ft/lb range so the unused strength will be there to resist the high pressures of shooting. :hmm:
Zonie,
Thanks for pointing that out. I have always thought that a breech plug tightened to "Strain Your Gut" torqe could weaken the connection. I call this "Crush Fitting". Rather than file and fit a little more someone decides to get a bigger wrench.
Does the strength in connection not come from the thread depth and number of turns rather than the tightness anyway? Not to say it should not be tight just not the kind of tight that will tear the top off your work bench when you try to get one out.
PD
Thanks for pointing that out. I have always thought that a breech plug tightened to "Strain Your Gut" torqe could weaken the connection. I call this "Crush Fitting". Rather than file and fit a little more someone decides to get a bigger wrench.
Does the strength in connection not come from the thread depth and number of turns rather than the tightness anyway? Not to say it should not be tight just not the kind of tight that will tear the top off your work bench when you try to get one out.
PD
As a glittering generality, yes, the strength of the threads is less as the length of engagement decreases.
On the other hand, thread engagement beyond one thread diameter is just going along for the ride.
Put in more practical terms, if you have a 9/16-18 thread, lengths of engagement longer than 9/16 don't provide for any significent increases in strength. :front:
On the other hand, thread engagement beyond one thread diameter is just going along for the ride.
Put in more practical terms, if you have a 9/16-18 thread, lengths of engagement longer than 9/16 don't provide for any significent increases in strength. :front:
