Shooting Platforms

[Terry C.]

DD, I have seen the shooting platforms in the photos. One thing I always wondered about was recoil. Some of the platforms look barely bigger than the carriages of the guns sitting on them. When I was shooting small caliber cannons (.45, .50, .54), I would get serious recoil from even mild charges.

These cannons look quite large for their bore size, so I imagine the extra weight makes them tamer than the very small cannons that I had. Even so, I have to wonder what happens when the guns fire. Are there some sort of restraints to keep them on the platform?

I always shot the smaller guns from a large plywood shooting platform because they were too unstable to fire with live rounds on bare ground. And I had restraints to keep the guns on the deck, otherwise they would have ended up several feet behind (and probably upside down or worse).

The ¼-scale Napoleon mounted on its carriage is almost three feet long overall, with 14½" wheels, and the barrel is about a foot off the ground. I've never felt the need for any shooting platform but I was looking at it from a stability standpoint. It never occurred to me that it might be more accurate if it was off the bare ground. On the other hand the grass and dirt surface helps control the rearward movement, which is several feet with a live round. I'm not sure what would happen on a really smooth surface.

Moderator Note: I have split this topic out of the How to Add Sights to Your Cannon without Drilling Holes as it was drifting the topic quite a bit. An actually they are two different topics.  DD

[Double D]

Here is the post that started the drift.

Something you may have noticed is the SAMCC guys do not shoot on the ground.  They all shoot from a platform.



They learned a long time ago the guns shoot better on a solid base.   Several of the older members who had difficulty getting down to the platforms  tried shooting from the Pistol range bench and from home made shooting tables and found the  they did not shoot as well as from the lower platform.  Even thought hey were sold they just weren't as solid as the platforms.  Go figure

I shot from a stack of phone books,



From on top of of a wooden box



From a plastic storage box with a rubber mat



And now from a purpose built platform with adjustable legs.   

The difference is like night and day. The wooden box and purpose built platform make all the difference in the world. The plastic storage box was ugly, the gun never shot the same two times in a row!

[Double D]

Yes some of the guns do recoil off the platforms.  Some more than others.



I think the issue of the need for a shooting platform is more a product of the Mass of the gun.  When my 1 inch gun is laid on grass you can feel the "sponge effect" when sighting on bare dirt it is not noticeable.  But I do notice it beat down a groove when fired.  It s kinda like shooting a rifle with loose screws.  It won't shoot as well as one that has tight screws. If the the cannon is sitting on a "spongy" base it won't shoot was well as from a more solid anchored base.

The little guns just don't have the mass to get big benefits from Ike Newtons 1st law.  The amount force applied to the mass exceeds the mass a great deal. 

I retire December 2008, determing if my gun shoots better with or with out a platform seem to be a good and worthwhile post retirement project.

I do know I would not build a platform like M&T's wit out sone serious means of restraining the gun.  Look real close at their platform  Thoss clamps are not for decoration.  None the less I bet that shooting bench moves whent he gun fires.

The club members have built alll manner of  platforms.  Some have bumpers at the back to stop the guns rearward movement.  Some field guns pop their trails over the restraint and come to rest with wheels on, trail of.  None come all the way off.  The ships gun, as they call them here, all come off if there is no bumper.  The platform I am shooting now even keeps the little club gun on the board.

Here is a collection of platforms from the club to give you ideas.












 

The last two and the fourth from the bottom are the Clubs top shooters with scores in the high 40's  and a 50 not uncommon.

[lance]

 I always like to get a few winter time projects going, i'll add a shooting table to the list. I took several minutes of DVD when Mike and Tracy came to town, closeups of their gun firing and recoiling on the table. gives me an ideal for a recoiling box of sorts to set my little cannons in, maybe some kind of track or runners for the box to ride on the table, with some method of brakes. Winter project! i'll figure it out........ Now that i'm thinking of it, a table would have been nice for the past few mortar games. the amount of powder i used wasn't enough to break an egg if the mortar was sitting on it anyway i'm still sore from getting up and down so many times off the ground.

[Double D]

A mortar will bounce on a table.  Take a look at the ground under your mortar after you fire it will be flattened.   I cannon will move a table also. Even with a recoil slide like you are describing.  I'll bet  when M&T get finished shooting if they look close they will see evidence where the rear legs dug in and the front moved.

The table has to be rigid with no flex.  Legs can have no spring and they have to  have some means to be kept from digging in.   Of course this isn't from experience shooting cannons off tables.  It from shooting Varmint guns off tables.  Start shooting cannons off table and the problems will be amplified heavier gun weight and recoil.  You would not believe how much a 22-250 can make a table bounce.  We were always pulling table legs out ofthe ground when blasting prairie dogs and gophers .  Even when shooting .22lrs

Take a close look at M & T's set up. 



I'm not sure what the table top is, looks like oak.  That should take care of rigidity.   It looks like a tripod set up for legs.  They are using  water pipe for legs. To me their legs look skinny...the table legs!!!   

I would opt for something heavier with a flanged bottom foot set up to sit flat on the ground to prevent excessive dig in.    I would also opt for quadrapod.  Shooting one time with double leg to rear and single to front then double to front  single to rear is going to affect the recoil impulse  and change how the giun shoots.  With a single leg, especially to the rear the recoil impulse is going lever on the outer side of the single ridgid point  and the table even an oak table is going to flex.

If you decide to tie down the gun to the table You want things strong and rigid.  I would look for some way to add weight to the front of the table to keep it down.

There's  my ideas Lance no fly at it.   I plan on retiring in December  2008.  Summer 2009 I am thinking having a GBO BPM&C cannon shoot.  So Lance get you table put together anbd bring it out to Montana and we will test it.

[lance]

 Double D, I was there all day with Mike and Tracy and their fancy table, in fact, that almost looks like one of the pics I took......... I did notice the weights fell off a time or two even got it on DVD.... I wasn't talking about full mortar charges, those weak loads for Walk the Walk, and Bingo. I recon 9 to 13 grains of powder and a golf ball might need a wrap or two of duct tape to hold that beast down on a table give me a little bit of credit, I might be silly, but I ain't stupid.....like i said my table will be a winter project, you'll get pics! i'll have all the bugs and testing worked out, if folks could fire full size guns off of wooden ships and mortar barges, I recon i can fire baby guns off a table .........summer 2009, Montana GBO mortar and cannon shoot, can i say: Hey Tim, ROAD TRIP!!!!

[seacoastartillery]

     Our multipurpose shooting bench works well for shooting everything from Win. 9422s to .303 SMLEs and beyond, like 1/6th scale Brooke Seacoast and Naval rifles (1.167" Bore Dia.) with almost 18,000 Ft./Lbs of muzzle energy.  BUT IT IS NOT PERFECT!  Double D, forever the keen observer, discovered a couple areas of possible improvement.  A very important one which always requires compensation is the open tube ends which DIG INTO THE GROUND every time we fire ANYTHING on this bench.  You can easily avoid this by welding a 4" X 4" flange on the end of each tube.  This bench was built 25 years ago; it's like the dog you grew up with; you don't want to ever change it and you always accept its failings.  We just throw three scraps of pine under the legs and it stops digging in. 
     The fairly rigid legs are thick-wall, 1.5" dia., aluminum tubes.  All three are bolted through a substantial flange with 1/4-20 carriage bolts and wings nuts to the bottom of the bench.  They don't loosen up because the nuts are tightened on the ALUMINUM FLANGE which binds steel nuts tight as most of you know. 

     DD is also correct about having two of the three legs to the back which is the cannon shooting configuration we use.  One leg to the back produces such wild and inaccurate results that we only tried it once!  We found that accuracy is much better if you connect your cannon to the weight of the bench if possible.  He is also correct about needing a weighted bench; if you look closely you will see 100 pounds of barbell weights hung under the front of the bench on the handles of two 12" "C"- Clamps.  We forgot to wrap a little tape around the handle ends in Virginia and the weights fell off a couple times.  Always bring Duct Tape with you!!

     The bench top is very rigid and is made from one 3/4" piece of cdx plywood sandwiched between two heavy pieces of 3/4" high density particle board.  The gun mount is made from 3/4" oak plywood and Baltic Birch plywood pedestals and 1/4" bolts.

     The whole bench and mount weighs 65 pounds.and 165 pounds when ready to shoot.  Before we added the barbells, the front of the bench was yanked upward 4 to 5 inches with each shot.  Not good for accuracy at all! 

   
Regards,

Mike and Tracy

[Double D]

Ah the ancient connoneers proverb...I have walked this path, and your steps are mine.

The modern Cannoneers proverb.   Been there, done that.


Now that's a well thought out bench.  At least with me the thought chain goes something like, if I do this, then I can fix that...
 
 Got a suggestion for feet.  Make some round pads say 8 to 10 inches in diameter. Weld a peg in the center set at the same angle as legs and with an OD of just under the ID of you leg.