Testing a Repro of the Tannenberg Gonne
This is a beautifully machined repro of the Tannenberg Gonne made by GGaskill.
Specs:
1. 1018 Steel
2. 3/8" diameter by 2" long chamber connected to a reamed .6875", 11/16”, approx. diameter barrel 8" deep.
3. Overall length: 13"
4. Maximum width: 1.6" across the flats, about 1.73" across the corners
5. Inside width of section for pole :1"
6. Outside width of section for pole: nominally 1.35" across the flats, 1.45" across the corners
7 Depth of recess for pole --- 1.5" plus 118 degree included angle point
The deal I made was to get the gonne and extensively test it – possibly to destruction.
Two types of lead ball were used .662” patched ball, average 428 grains and .678” ball, average 469 grains.
The chamber proved to have a powder capacity of 57 grains by volume. By compressing with a dowel, I could get several more grains in.
I used Goex powder, 2f, 3f and 4f for a variety of tests. Since this was partially an attempt to damage it I was continually checking the dimensions which explain the lines on it. The measurement points were every inch except in the chamber and the breech area where it was every ½ inch. Here was the test platform so I could be safely away for the proof loads:
It was build stoutly of scrap hardwood, heavy screws, bolts and glue on a plywood base. The rear was especially strong and designed so it could easily be raised vertical for pouring and ramming. The short tiller was held in place with a hardened ¼” bolt held by a thumbscrew for easy removal for cleaning & measuring.
I built the platform fairly rigid in hopes that it would allow an inaccurate handgonne to be accurate enough to use my chronygraph without blowing up the sensors or skyscreens. That worked out fairly well. It was a blazing hot day at the range so after awhile the chronygraph lost its little mind.
I was also hoping to test penetration of sand with some 5 gallon paint buckets and sand IÂ’d salvaged from a construction site. That did not work well. The balls shattered the buckets and the sand ran out.
Here are some velocity reports. The figures will be reported by powder charge, ball diameter, average velocity in feet per second and energy in foot pounds.
57 gr 2fg, .662, 542 fps, 280 foot pounds
57 gr 2fg, .678, 406 fps, 171 foot pounds
62 gr.2fg, .662, 541 fps, 279 foot pounds
62 gr. 2fg, .678, 460 fps, 220 foot pounds
57 gr 3fg, .662, 427 fps, 173 foot pounds
57 gr 3fg, .678, 377 fps, 148 foot pounds
By comparison, a.45 ACP 230 grain bullet moving at 900 fps has an energy of 413 foot pounds.
The first two series were five shots each. In the third I messed up a patch and got a very, very low speed so I left it out. As the series went on, I got more and more goofy readings until the last one had one possibly correct reading. I left out other series since I had no way to measure.
I loaded the gonne with 4f which did sound louder but the dimensions stayed the same.
The it was time for proof shots. Not one proof shot but four! Double charge of powder – 114 grains and double balls, either two patched .662 balls ot two lubed .678 balls.
I wish I had all the goodies like the Mythbusters show, lexan blast shields, high speed camera and such. Instead I used a long fuse and left the berm. The shots sounded loud but once again the gone was unchanged in dimension. By the end of the proof shots the ¼” bolt holding the tiller was badly bent and hard to remove but the platform was intact.
The conclusions are that this is one strong gonne. The chamber is undersized for such a heavy piece of steel. GGaskill says boring it out to 7/16 would increase volume by 36% which would give a capacity of about 78 grains. IÂ’m tempted to try that but then IÂ’d have to do more testing. It is such a good looking gonne. It would be a shame, but fun, to blow it up.
If youÂ’re not totally bored by now, the link to the full report is:
http://www.crufflersteve.net/gonne_rpt.docSteve
