Convertible?

[shootemup]

Anybody have first-hand experience with a gun that would go back and forth between flint and percussion locks? I'm seeing issues in my mind, but am curious to hear from someone with actual experience...

Spot

 

[William Joy]

I had built a fullstock Flintlock rifle which had a conversion to Percussion for a customer. I will no do it again. First of all the drum MUST be supported by the lock - on the other hand the ventliner in the Flintlock then will not be perfect...
By changing from drum to Ventliner often you " ruin " the timing of the drum / wear the threads. I also had a problem to have a quality trigger, since I normaly fit the trigger to the lock - now I had to deal with 2 locks...
I believe if you want a percussion and a Flintlock buy to guns!

 

[shootemup]

Yep, sorta what I figured. It's the novelty thing that had me interested, thanks for the response.

Spot

 

[54mountain]

I converted a percussion to flint with the idea of being able to go back and forth, but once I got the flint lock tuned I see no reason to ever go back. :grin: I think I'll make a pistol with my leftover percussion lock :thumbsup:

 

[Stumpkiller]

Ah! You beat me to it.

I know Dixie had such options in the past but folks tend to choose one and stick to it.

A firearm that can do both is the best of neither.

 

[kencolamarino]

You can do this with the Pedersoli PA, Scout, and Kentucky rifles. First you buy the percussion model because it already has the drum installed and timed. Then you buy the replacement flintlock and a vent liner and you are in business. The replacement flintlock is available from a number of Pedersoli rifle suppliers.

 

[Zonie]

I've built two guns that are "convertible".
I will admit that I've only changed them back and forth a few times but I've had no problem with the threads wearing out.

Building these is a pain in the A** because not only does the builder have to custom fit the drum and percussion lock so that the lock supports the drum but the sear arms have to be adjusted so that they both release with the same trigger setting.

Also, although the commercial locks look the same, the lockplates are slightly different so to fit in the same lock mortice minor adjustments need to be made to them.

Then there is the shooting difference.
For someone hunting where a 2 or 3 inch change in impact isn't a real big deal if the guns are going to be used for target shooting it becomes a big deal.

Because the flintlock uses a comparatively large touch hole as compared with the .028 hole in the typical nipple the pressure in the barrel drops faster. That means the ball will hit lower if the same powder charge is used.
This means that if the sights are adjusted for the percussion lock the only way to bring the flinglocks shots up to the point of aim is to increase the powder charge a bit.
Finding "a bit" can be frustrating which explains why if a person has a "convertible" lock rifle they will often just say to hell with it and go with his/her favorite style of lock.

Needless to say, a convertible rifle also costs more to build and to buy.
It's one of those things that sounds really neat until it is seriously thought about.

 

[CoyoteJoe]

I once built a mule-ear side-slapper lock to fit my Blue Ridge flint rifle. With a side slapper there is no problem of fitting up a drum and keeping it fit up, you just replace the vent liner with a percussion nipple. Of course that requires a custom made lock.
The best approach for a convertible gun is to use two barrels as well as two locks. I have a T/C Renegade with a .54 Sharon percussion rifle barrel and a 20 gauge half octagon tapered round smoothbore mated to an RPL flintlock. That makes a true "two in one" combination gun and change over takes but a minute. :grin:

 

[Sharp Shooter]

You could do it in about 5min. You just change the barrel and lock. Have a flint and percussion barrel and two locks.

 

[Otter]

Spot,

I had one built for me 5 years ago with both ignition systems and have had no problems, but as Zonie said, I don't swap them out often - I've only changed from flint to perc and back once. I can't tell the difference in trigger function from one to the other. Maybe my builder just did it right or mine is an anomoly. I, too, had concerns about galling the threads with the vent liner/drum swap, so when I do swap I am very careful to be very careful. Drop me a PM and you can stop up sometime after you get off work to see it or, better yet, we could go out and shoot it . . .

 

[shootemup]

Thanks Otter,

That's very kind of you. What sparked my interest was a rifle I ran across that has this set up. I was curious as to what sorts of problems might go along with something like that.

I have to say, the issues that were pointed out had not crossed my mind, so I learned something here...

Thanks all -

Spot

 

[Zonie]

I have heard of and seen threads damaged in several ways.
There is the common "cross threading" that most everyone is familiar with. For those who don't know, if the male thread is started into the threaded hole slightly cocked it will act like it is engaging but it instantly becomes very hard to turn.
If it is forced the threads on both parts will be deformed and ruined.

Then there is "overtightening". This is a common cause of threads "wearing out" and becoming "loose" after the male part is installed and removed several times.
This (IMO) is the main cause of drums, vent liners and nipples "wearing out".

For the record, here are the recommended MAXIMUM torques for threads in mild steel (like your barrel and drum) parts.

1/4-20 = 57 Inch Pounds (4.7 Ft/Lbs)
1/4-28 = 77 Inch Pounds (6.4 Ft/Lbs)
5/16-18 = 95 Inch Pounds (7.9 Ft/Lbs)
5/16-24 = 103 Inch Pounds (8.6 Ft/Lbs)
3/8-16 = 172 Inch Pounds (14.4 Ft/Lbs)
3/8-24 = 196 Inch Pounds (16.4 Ft/Lbs)

If you are familiar with torque/load tables and you notice these values are reduced there is a good reason.
Normal thread installations are for static loads.
In your gun, there is also the pressure load during firing to deal with.
I have reduced the torque values to accommodate a breech pressure of 12,000 PSI so that the thread material will be able to accommodate these added forces without exceeding the yield strength of the barrel and drum, vent liner or nipple.

If these guidelines are followed the drum/vent liner or nipple threads can be assembled and disassembled hundreds of times and there will be no significant wear or loosening under normal fastener service.

Even you folks who aren't swapping locks and vent liner/drums should pay attention to the values given because whenever you replace a nipple, drum or vent (not to mention a breech plug) you do not want the torque value to use up all of the threads strength.

By the way, the above torques will be more than enough to prevent a drum, vent liner or nipple from "working loose" unless a "friend" grabs some pliers and tries to remove them.