Author Topic: barrel vent repair  (Read 1110 times)

Offline bob in the woods

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barrel vent repair
« on: August 21, 2022, 09:45:44 PM »
The vent on my 4 bore needs repair. I have what I need to drill and install a 1/4-20 plug but wondered if a 3/8-32 would be better considering the bore /barrel size ?

Offline Bob Roller

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Re: barrel vent repair
« Reply #1 on: August 21, 2022, 09:50:54 PM »
I would stay with the 1/4x20 or maybe the 1/4x28 and then IF needed the 3/8x32. How thick is the barrel at the breech on that big bore gun.
Bob Roller

Offline bob in the woods

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Re: barrel vent repair
« Reply #2 on: August 21, 2022, 10:29:57 PM »
Thank you for the reply, Bob.  I just checked..the breach is 1 and 3/8ths inches across the flats

Offline smylee grouch

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Re: barrel vent repair
« Reply #3 on: August 21, 2022, 11:51:11 PM »
Maybe the length of the flash channel might dictate which size to use.  :-\

Offline Bob Roller

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Re: barrel vent repair
« Reply #4 on: August 22, 2022, 01:56:43 AM »
Maybe the length of the flash channel might dictate which size to use.  :-\

Yes,measure the wall thickness of that barrel. I have no idea what the diameter of a 4 bore hole is.
Bob Roller

Offline bob in the woods

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Re: barrel vent repair
« Reply #5 on: August 22, 2022, 02:32:54 AM »
Bore is .990 inches

Offline Bob Roller

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Re: barrel vent repair
« Reply #6 on: August 22, 2022, 02:48:11 AM »
According to my little handy dandy calculator that wall thickness is 7/32. I'd go with the 1/4x28 for the additional threads and try for full depth.
Bob Roller

Offline bob in the woods

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Re: barrel vent repair
« Reply #7 on: August 22, 2022, 06:34:56 AM »
Thank you for your recommendation , Bob.  I believe I have a 1/4 -28 in the shop ...somewhere  ;D

Offline Bob Roller

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Re: barrel vent repair
« Reply #8 on: August 22, 2022, 02:28:00 PM »
Thank you for your recommendation , Bob.  I believe I have a 1/4 -28 in the shop ...somewhere  ;D

You're welcome.I case anyone is wondering how that figure was obtained,it's simple math. I used the breech
diameter of 1.375 and subtracted the .900 bore and the divided that number by 2 and came up with .2375
so the 1/4x28 if threaded to full depth or close to it should stay in when the gun goes off.Another hint,
counter sink the hole you'tr going to tap to the depth of ONE thread,That will make the tap easier to start and leave
a better looking job as well.
Bob Roller