Interesting osbservation at the SAMCC cannon shoot

[Double D]

Those of you who are regulars here, know that while I am down here in South Africa I have been shooting in the monthly club shoots of the South  African Miniature Cannon Club held the first  Sunday of every month.  The Club has graciously loaned me one of the clubs cannons to shoot.

I have been getting the gun dialed and and finally have got it shooting pretty well.  Because of the way the trunnions are mounted and the fact that the muzzle swell is over sized the gun is muzzle heavy.  In order to pull the back of the barrel down a rubber band is pulled over the cascabel.



We haven't shot for two months due to weather and the club taking part in the Swartkop Challenge. The club gun was used to start the races.  I noticed this morning that the rubber band was a bit frayed so I changed it.  The rubber bands I have been using were wide flat bands that were pulled over the cascabel and the ends hooked over the wheels.  The replacement band was a narrow thick band that was to long too just hook the ends over the wheels, so I doubled the band. 

My first 4 shots were 8 inches high.  I was able to pull my next two shots down into the black by adjusting the elevator.  When I fired my first shot of the second string one end of the  band broke.  Because the band was double it didn't let loose, so I left it.  My shot from when the band broke went high.  My next two shots went clear over the top of the target and the band let go.   I rummaged around in my shooting box and found a wide flat old style band and put it on.  My first shot with the new band went way low on the target.  I adjusted my aim to what I normally use and got two in the black, the last one being a pinwheel ten!

I would have never thought that rubber band pressure would have such adrastic effect

[Santa Dave]

Can you/ have you tried shimming the fit of the capsquares so they are tighter on the trunions? it would appear they are loose. and with the band between the trunions and the elevator it Might have some effect. (But I'm surprised at the amount)
Dave
The more we mess with these the more we learn!

[jeeper1]

I just checked the video clip of my little howitzer firing and even though it is muzzle light and semi snug in its mounting, upon firing the muzzle drops.
http://www.youtube.com/watch?v=S1_suk7uq7c

[Double D]

I knew there was/could be some bounce, but I didn't realize what a profound effect something like the amount of tension applied by a rubber band would have on point of impact.

I am getting ready to build a gun and what I have been thinking about doing is  making solid one piece cap squares. I'll make the trunnions a tight but not binding fit. 

Barrel bounce is easily observed in all the club guns when the fired but only two guns have bands to hold barrel. The secret would seem to be to have a consistent bounce.

So I think I need to get a bag of rubber bands and check them for consistent pull and change the band every match...does any one know where I can get match quality rubber bands?   

[Will Bison]

I noted the breech bounce some years back. My accuracy is better now that I tie my breech down. It happens so fast its hard to see with the naked eye but digital video sure sees it.

Bill

[GGaskill]

...any one know where I can get match quality rubber bands?

How about using enough to eliminate the bounce?  Make it real tight.

[Rickk]

Any way to add a weight (a flat metal plate of steel or lead for instance) under the barrel and instead of a rubber band, use a heavy wire loop attached not to the carriage, but to the weight? One end of the plate would rest on the carriage and the other end would be supported by the wire loop.

That would make it rear heavy but maintain elevation adjustability. A stiff wire would not stretch like a rubber band, so there would be less variability.