Question regarding installing percussion drums.

[Rolf]

Is it safe to install a 7/16" drum on a 3/4" oct-round barrel?
Does anyone make smaller drums?

Best regards

Rolf

[Dave Dolliver]

I assume that you mean 7/16 " is the drum diameter not the thread diameter.

I have seen 7/16 and also 1/2" diameter drums both sizes with 1/4-28 threads, 5/16 dia threads and 3/8 dia threads.  The smaller the thread size, the stronger the installation is if done properly.  Since the barrel wall thickness is constant and the drum is loaded as a "plug"; with the larger threads the load goes up as the square of the diameter and the strength of the installation goes up as the first power of the diameter.  It seems as though most are fearful of the 1/4-28 threads but I prefer them for several reasons, strength being but one of them.

Dave Dolliver

[T*O*F]

Rolf,
Drums are generally measured by the thread diameter, not the drum diameter.  That is 1/4", 5/16" and 3/8".  You should use the one that will fit within the side flat of the barrel.  It should have fine threads rather than coarse ones.  Then you have to fit your lock bolster to the diameter of the drum.  The drum must be supported by the lock with no gaps.  If the bolster is already cut and is too large, you can always fit a brass shim in the gap and solder it to the lock.  Otherwise, you file the bolster until it fits your drum.

[okieboy]

 Dave, I believe that the dislike of 1/4-28 threads is not per se with the thread itself, but with the fact that a 1/4" diameter with a hole drilled down its axis leaves uncomfortably little material to stand up to the repeated hammering stress produced by the lock (even with a good installation). I have a couple of 1/4-28 drums that I bought years ago, but they will never be used.

[Dave Dolliver]

Yes, if the drum is not installed so that it is tight against the lock plate the threaded portion would be loaded in shear which is undesireable.  so we try our best to install them tight against the lock plate no matter what the threaded diameter might be.  I haven't had one fail yet and I do like them especially on the 13/16 barrels that are common on light weight rifles.  They also are convenient to use when a 1/4-28 touch hole liner is to be used on a convertable with both flint and percussion locks that I have been asked for at times.  But do get them tight against the lock plate.

Dave Dolliver

[Roger Fisher]

Yes, if the drum is not installed so that it is tight against the lock plate the threaded portion would be loaded in shear which is undesireable.  so we try our best to install them tight against the lock plate no matter what the threaded diameter might be.  I haven't had one fail yet and I do like them especially on the 13/16 barrels that are common on light weight rifles.  They also are convenient to use when a 1/4-28 touch hole liner is to be used on a convertable with both flint and percussion locks that I have been asked for at times.  But do get them tight against the lock plate.

Dave Dolliver

Assuming ol Rube has his lock plate inletted and finds a frog hair space between his nicely fitted drum and the lock plate and is contemplating upsetting the bolster cup for the drum (cold forge)inside and out, should he proceed w/his idea as a more simple fix than soldering the brass shim or would he be thrown outta the club for using such a Rube Golberg fix

[T*O*F]

Ol Rube,
Your simple fix will probably end up as a lot more work.  By upsetting your bolster, you will only raise the edges, which will not support the drum along its entire axis.  Then you will have to file the peening marks off your plate.  It is much easier to wrap a thin piece of brass sheet around the drum to shape it and then solder it to the bolster.  Sandpaper wrapped around an appropriately sized round object will complete the final fitting in minutes.

[Roger Fisher]

Ol Rube,
Your simple fix will probably end up as a lot more work.  By upsetting your bolster, you will only raise the edges, which will not support the drum along its entire axis.  Then you will have to file the peening marks off your plate.  It is much easier to wrap a thin piece of brass sheet around the drum to shape it and then solder it to the bolster.  Sandpaper wrapped around an appropriately sized round object will complete the final fitting in minutes.

I'll tell him

[keweenaw]

Rolf,

Percussion drums are really easy to make on the lathe and I find that it takes less time to install a blank one and then drill and tap it for the nipple than it does to align one that has the nipple hole pre drilled.  Either 1/4" or preferably 5/16"NF threads are ok as long as the shoulder of the drum is up tight against the barrel flat and the drum is supported by the lock plate.

Tom

[Dphariss]

Is it safe to install a 7/16" drum on a 3/4" oct-round barrel?
Does anyone make smaller drums?

Best regards

Rolf

I would recommend you not use a drum.

The problem with modern drums is they are invariably made from brittle, free machining steels. These have very poor resistance to shock such as when the hammer strikes the nipple and the way they are machined may make them even weaker in this regard.
If I build a percussion I use a patent breech.
Dan