White Lightning vent liner- Do's and Don'ts

[Nordnecker]

This is a spin-off from another thread, "Breech Plug Question". I don't mean this to be a tutorial, just an account of tips and trials. Please step up and correct me if I'm wrong- another DON'T.
I have often thought that "How To" instructions should also come with "How Not to Do" instructions. When considering a vent liner, the first consideration should be whether or not it will fit in the barrel without hitting the breech plug. So this means positioning the lock forward enough so this won't happen. Giving credit where credit is due, it was Dennis Glazener who told me to wait on installing the liner untill the barrel was inlet and the lock installed. In other words- DON'T install it until you can line it up with the pan, not the other way around.
And DON'T position your lock so far back that the liner ends up in the breech plug.

I had ordered my liner from Jim Chambers and he offered to send the appropriate drill and tap with it. I accepted his offer- That's a DO.

I read the instructions included and followed them as best I could, another DO.

I tried to stop the tap from going all the way through, but it wouldn't seat properly and I ended up tapping it a little deeper. It went all the way through and I thought it was wrong, but it did seat it the countersink. I thought all was well, cut and filed the liner and put the gun back together- DON'T. After running my cleaning scraper down the bore, I realized it was hitting the liner inside the bore. So I had to take the barrel back out, remove the breech plug and grind the liner off INSIDE the barrel. DON'T. Fortunately this was a .54 smoothbore and it was not a problem.

The light bulb went off this morning when I read KYflinter's post in the other thread. DO leave the extra material and screw slot on the liner until you know all is well on the inside of the bore. DO NOT cut it off until you know and correct it.

So now I'm getting ready to put a liner in another barrel. It's a 13/16 .40 rifled barrel from Getz. I had measured the wall of the barrel and saw that the liner was longer than the wall of the barrel, so this same thing is going to happen. I don't know how to gauge the length I should leave. I mean, What if it breaks through where the rifling crosses? Or is the wall thickness too thin to start with? Maybe it's not even thick enough to worry about a liner.

So for now I'm at DON't do anything just yet.  What would you do?

[E.vonAschwege]

Nord - great listing of DOs and DON'Ts for installing a White Lightnin liner.  I agree with all of the tips, and I do always try to make it so the liner doesn't interfere with the breech plug.  Sometimes despite our best efforts that isn't possible, and it is considered by most to be an acceptable practice to dish the breech plug SLIGHTLY (the amount depends on the depth of the plug, I've dished by 1/16" before) if needed to accommodate a liner.  This of course means the liner must be measured for depth, filed so it doesn't protrude into the bore, breech plug installed, then liner installed, locking it all together. 

Your 13/16" .40 barrel will have .206" barrel wall.  Using the 1/4" -32 liner, the math shows that's room for 6.5 threads, but realistically with the slight countersink combined with depth of the rifling, it gives you 4 to 5 threads, which IMO is still reasonable on this small liner.  You can always drill a touch hole and then cone it from the inside slightly, see how it works, then worry about a liner later if need be. 
-Eric

[E.vonAschwege]

A side note - Track of the Wolf sells "White Lightnin" liners as well as Jim Chambers, however they are NOT the ones made by Chambers.  Same specs, but the Chambers ones have a better inside finish. 

[okieboy]

 A question Evon, won't a lot of the outside bottom of the liner be captured under the bottom of the lock's pan, making the number of threads engaged something of a moot point? Not saying that more isn't better, but where is it going to go with part of the lock fence against it?

[E.vonAschwege]

The lock bolster should be tight against the barrel flat and part of the TH liner, but the lock and barrel are separate entities and must be thought of as such.  A lock should never be relied upon to hold the liner into the barrel.  I'm not an engineer, but a mental picture comes to mind of Wiley Coyote trying to hold the door closed so the freight train doesn't come through it - we all know how that ends.  I'm not trying to be a wise guy, I just think proper thread engagement is imperative when installing a TH liner.  I prefer to avoid them when I can  . 
-Eric

[Jerry V Lape]

Would it work to not tap the hole through.  Then screw the liner in and measure the excess; remove the liner and file some excess and repeat this process until the liner is seated both in the hole and in the countersink?  I haven't done it this way having tapped it all the way through in the past before filing excess.

How many full threads are enough to ensure the liner stays put? 

[PPatch]

Would it work to not tap the hole through.  Then screw the liner in and measure the excess; remove the liner and file some excess and repeat this process until the liner is seated both in the hole and in the countersink?  I haven't done it this way having tapped it all the way through in the past before filing excess.

How many full threads are enough to ensure the liner stays put? 

That is the way I did the last one. Once I had the flange seated I sawed off the remainder and peaned the flange then filed it flat.

dave

[BJH]

One thing I do after prick punching the final location, I pilot drill with a 5/64 drill bit. Put the barrel back in the stock and verify the location. Yes, belt and suspenders.f   Then I countersink the hole almost to the finish diameter. Then I tap drill. Why? Because the countersink is less likely to chatter, also the tap drill will self center in the countersink. The small pilot hole will allow you to fudge a slight error in location for correction at the countersinking stage.  BJH

[Nordnecker]

Wasn't there a thread a while back that said to drill the touch hole out to a 16th of an inch?

[Karl Kunkel]

Nordnecker,

Yes, there was.  It's been discussed several times in the past.  It seemed that many open up the touch hole to 1/16" to start.