Barrel thickness for vent liners Getz 13/16" straight barrel at .50 cal

[Birddog6]

I would like some opinions.  I have a .50 cal  13/16"  Getz straight  barrel with round bottom rifling.  I am looking at vent liners to put in it.  If I use a Chambers white lightning vent liner which is 1/4 x 32 threads, it will catch 3 threads if it hits dead in a groove & 4 threads if it hits on the lands.  If I make a vent liner from a SS bolt I can easily get a full 4 threads & if I don't use as much of a seat as the  Chambers vent liner, but still cone the inside of the vent liner, etc.

Question is:  Do you think 3 threads on this barrel is enough to hold the vent liner ?

Or should I make a vent liner & go for the full 4 threads ?

Or do you think I should drill it straight & not use a vent liner at all  ?

Now one guy told me it would be OK on a .45 cal but not on a .50 cal.  I got to thinking on that & we are talking about the dif of .0025" in wall thickness.   I just can't believe a dif of  2 1/2 thousands of a inch will make a dif of it holding or failing.      Seems to me you could screw that much up just by having a lousy tap & making sloppy threads......

Thanks

Keith

[billd]

Keith, 

Don't you mean .025, not .0025?  That's .050 total, .025 per side.  About 3/4 turn on a 32 pitch thread.

Bill

[B Shipman]

Birddog, back when I used to repair things, gas cut vent liners in 7/8 in. and 15/16 in. .50's were common. Granted, these were usually Ampco liners but they were also thicker.

What I would do is simply do an external cone. The 30 deg. chamfer tool that Dremel has is perfect.

[Dphariss]

You need a patent breech or a "plain" vent.
Dan

[Birddog6]

Keith, 

Don't you mean .025, not .0025?  That's .050 total, .025 per side.  About 3/4 turn on a 32 pitch thread.

Bill

Yes, had one too many 0's in there. Thanks.  it is .025 if in the wall thickness from the .45 to the .50.

Anyone know how many shots a  1/16" vent hole in the barrel would last ?  We talking 1000 shots or we talking 5000 shots under normal loads ??

Thanks

Keith

[Birddog6]

You need a patent breech or a "plain" vent.
Dan

Possibly for the next one, maybe one with a flash channel direct to the center of the breechface, but not the standard patent breech, as I don't like that right angle flash channel. 
Then finding a breech I like for a Lancaster rifle in a 13/16" is another issue. Most of them I see are for Hawken rifles, fowlers or English ones.  Guess I could cut one off & weld a std flared tang to one of them.

In this case I have the barrel in the rifle& where I want it & getting ready to do the tang & just undecided about the vent liner.

Thanks

Keith

[Dphariss]

You need a patent breech or a "plain" vent.
Dan

Possibly for the next one, maybe one with a flash channel direct to the center of the breechface, but not the standard patent breech, as I don't like that right angle flash channel. 
Then finding a breech I like for a Lancaster rifle in a 13/16" is another issue. Most of them I see are for Hawken rifles, fowlers or English ones.  Guess I could cut one off & weld a std flared tang to one of them.

In this case I have the barrel in the rifle& where I want it & getting ready to do the tang & just undecided about the vent liner.

Thanks

Keith

The plain flint breech is the same as a flint patent breech unless a Nock breech is used. They are all 90 degree.
In a barrel this small you end up with a chamber in the breech that is smaller than the bore but thats a penalty for using a barrel too small at the breech BTDT.
Your best choice may be to thread it deeper and use a chambered breech plug. This was often done on English  fowlers.
 Set the vent back far enough to clear the cup and make sure the powder channels are large enough .100-.125" for FFFG and FFG and everything is good. Should be fast and as reliable as anyone could want.
Actually something like this.


Not much of an artist but its the general idea. Wish I had done this for the swivel its 13/16 50 cal. "Cup" in the "art work" is a little larger than it should be. Smaller cup will give longer vent threads. I would likely use a 7/16 ball mill for the cup. Even a 7/16 drill would work but less "elegant".
Should not present any cleaning difficulties.

Dan

[Birddog6]

That would definitely work, but then I have the barrel & breechplug locked by the vent liner & I an no crazy in love with that. 

Gonna think on this a while.

Thanks for the input.

Keith

[Dphariss]

That would definitely work, but then I have the barrel & breechplug locked by the vent liner & I an no crazy in love with that. 

Gonna think on this a while.

Thanks for the input.

Keith

Unless you need the barrel recut there is little reason to pull the plug.

Dan

[Birddog6]

I wish Don Getz would get on here, but I think his computer is still down.  He told me they tested these barrels when they made them, but I don't know if they used a vent liner or just a vent hole or what.  In fact, these barrels were discussed on here some time ago.

[Roger Fisher]

I wish Don Getz would get on here, but I think his computer is still down.  He told me they tested these barrels when they made them, but I don't know if they used a vent liner or just a vent hole or what.  In fact, these barrels were discussed on here some time ago.

Yes, and they really loaded them up!

[Birddog6]

Don Getz:  I see your computer is up & running. 

When you guys tested there .50 cal  13/16" barrels, did you use a vent hole or a vent liner to test them ?

If a vent liner, what liner did you use ?

What charges did you test them with & how many times did you fire them ?

Thanks   

Keith