Punt Gun Possibilities

The boat above in Loki's picture is similar to the kayak canoe I know as the PBK type, which is a light wooden frame covered in Canvas which then gets a waterproofing "Dope" paint.
I had one for many years.

Mounting a Cannon on one?... forget it.
The frame is just not strong enough.

Variations, the Canvas can be replaced with light wooden sheeting, which again is painted with waterproof, ..
It maakes the craft heavier, but not necessarily stronger...
Not strong enough to support anything over an average human weight.

The craft, although on a trailer there, was supposed to be easily portable by one or two men.
That does kind of limit the weight.....

at risk of being viewed as sadistic and cruel, what about shoulder firing a punt gun?

would a punt gun charge knock a man over as in the movies? (I.E. replicate the results)

OK, the basic idea here seems solid enough for the show and has everything needed for an interesting episode as well as plenty of scope for both supersizing and smaller scale tests.

Now, how could this be tested safely?

The quarry lakes they have used do have high hills around them, and using pellets rather than solid shot should eliminate any risk to anything/anyone on the other side of those hills. (It is highly unlikely that the shot would bounce over the hill as it did with their cannon). However they need to find a way to make sure that the boat and its gun is always pointed in a safe direction, and will not drift out of line.

Using an anchor is a none starter, since this would absorb any recoil. Maybe they could get two floating platforms that are anchored in place, with a small gap between the two of them where they can place the boat. This would allow them to keep the boat pointed in the right direction, and as an added advantage would allow them to not only see if the boat moved backwards by having something stationary to measure any movement against. But the platforms would also give them a stable place from which they could work from, which would help reduce setup (and reset) times by allowing them to keep the spare ammunition and even other guns on those platforms rather than having to row them out to the boat between shots.

A platform might also make it possible to test a true cannon, as they could secure the cannon to the platform with ropes so if the boat were to spring a leak or prove unable to take the weight they would not have to worry about having to dive down to the bottom of the lake to recover it. Even if the boat were to sink with the cannon the ropes would let them pull the cannon back out in a matter of minutes without anyone having to get their feet wet.

That seems to be a fairly simple and straightforward rig to me.

Punt guns with a bore of 1.5 inches, firing a pound and a half of shot at 1000 f/s with 3 ounces of blackpowder, were considered as 'average size' 150 years ago. such a gun weighed around 100 pounds.

Recoil was considerable, but several systems were used to avoid having the punt torn apart when the gun was fired. Rope breeching, with ropes running through blocks to bring the recoiling gun to a halt were common, while several mountings using springs, hydraulic rams or even solid blocks of rubber were available.

Could a standing man fire one if the barrel was supported? Certainly. Would he still be standing afterwards? Only if he could stop a 100 pound gun, moving back at around 20 f/s, before it knocked him off balance.

If a 150 pound man was hit by the full charge of shot (assuming none passed through him) he would be shoved back at 10 f/s. 'Blown away', no, but certainly knocked over.

And yes, the punts do move back. The punts are light, and the water offers little resistance - after all, they're propelled with little more that table tennis paddles.

After firing the punt gun, the gunner used a light gun such as a 4 or 8 gauge to finish of any cripples.

Too complex for what is needed. All that is needed is a simple way to ensure that the boat will remain pointing in the right general direction - which if they use one of the quarry lakes will be a hill. The risks here are not about the shot passing over the hill, since they would be firing pellets rather than solid shot and these have a much shorter range. Rather the risk is if the boat were to turn around and point in the direction of the crew. While they are not going to fire the gun when it is pointed in their direction, it would be a hassle to reset the boat every five minutes.

Lights idea of guide ropes would be the simplest and quickest method, while my earlier idea of a floating dock is more complex but might give them more options for filming and allow a recovery system to be employed should they be able to use larger and more expensive guns - such as a genuine cannon.

I'd guess that they would pick a boat based on the size and weight of the guns it will have to carry. They would not, for example, want to put a cannon into one of the wooden boats they used for the hailstones myth. Even if the cannon didn't go straight through the keel when it was put in the boat, the recoil would most likely shatter the frame. An educated guess would be that they would use an old speed boat hull or something similar. This would be large and strong enough to handle any gun they are likely to be able to use while not being so large that transportation would be a problem.

Ideally they would want to use the same boat for all the tests - or at least the tests involving the more powerful weapons - and a relatively light speedboat hull would be ideal for this.

Good point privatepaddy.

Here's a suggestion that would eliminate some of the variables and challenges: Basically take Cyber's idea of a dock, but build it on the ground at the bomb range over a tank of water instead of going to a lake. The tank just needs to be long/deep enough that you would get the same basic water resistance against the boat when the shot goes off. That way you'd be able to almost - if not entirely - eliminate the factor of wind and any filming or recovery troubles. Plus it just seems safer to me. Less stuff that can go wrong.

if you submerge the rope, not much.

Ok I really shouldn't address this but I will.
What happens to submerged rope?
What happens to rope that is free to travel through eyelets?
What happens to the boat if one side of the rope is heavier than the other?
What happens to the experiment with effectively a sea anchor at either end?

The 'rope' would be steel cable, and its job is purely to help keep the boat pointing in the right direction - although it could have a secondary role in giving something against which any movement could be measured.

This would be fairly simple to set up, as they would have no problems getting a spool of cable that long - and it need not be that thick as it doesn't have to take that much weight or force. They would need to have a solid pylon at both ends, one of which would probably need a powerful winch to pull the cable in, but this is also fairly simple to set up.

Not that this rig is without problems. First is that setting up shots would either require rowing out to reload the gun - time consuming, on a small boat loading could be difficult and if the boat were to be damaged and take on water there is a very real risk that they could end up with an expensive gun at the bottom of the lake that would probably have to be recovered - which could take hours if not days and require heavy lifting equipment if we were talking about a full sized cannon.
The second problem is that at least one of the platforms is literally going to be in the line of fire, as is at least part of the cable. It is unlikely that 'grapeshot' is going to do any real damage at range, but the potential is there for a shot to damage the rig.

The idea of testing on land in a man-made pool does strike me as being an excellent idea. A long pool (and it would need to be some 20-30 feet long and at least 5 feet deep and 5-6 feet wide to accommodate a boat capable of taking a cannon as well as giving enough room to allow for any recoil) does seem practical, if challenging.

This would solve a fair number of problems, since such a rig could be taken to wherever they decide to conduct their testing - most likely not the bomb range given what happened the last time they fired a cannon there. The only problem might be in getting the water to fill it, since several of their test locations are unlikely to be connected to mains water supplies. Testing on the shores of the quarry lake might be ideal here, as they could simply pump water from the lake into the pool and let it flow back in after testing*. It would also give them the option of putting the boat and its gun onto the lake so that the cast could test this out while on the boat if it seems safe to do so.
There would be no risk of loosing an expensive gun to the lake. At worst a gun is going to end up in a couple of feet of water, from which it could be removed quickly and easily - after all they would need a platform to film on and a rig to help put larger guns onto the boat, both if which would allow them to pull a sunken gun out of the water before there is any risk of it being damaged. (Unlike if it were to sink into the lake, where impact with the bottom could damage it).
Last of all as far as safely firing the gun goes, if they are firing over the lake at the hills then the chances of shots going wayward are effectively zero - at that sort of range grapeshot would simply not have the range to get over the hills even if the gun was fully elevated.

The only problem that would need to be overcome would be the design of the 'pool' and its dimensions - the latter would depend on what boat or boats they are going to use for testing. But this seems like the sort of build that MB love to sink their teeth into - and if (as seems likely) this pool is designed so it can be built in the shop and set up on location it would give them something they may be able to reuse on future shows where they want or need to do water-based testing safely.
Of course they could always go with the cheap and simple pool design they used for swimming in syrup - just dig a big trench and put waterproof lining in it.

(*I've seen nothing to indicate that SF is having to restrict water use, even after the recent fires around the reservoirs. But wasting something like 7,000 gallons** of drinking water might not go over well.)

(**Figure is based on my very rough estimate of the required size given above. The figure is for US gallons.)



Basic physics, a blank round does not have the same recoil as a normal round as the former is not propelling any significant mass out of the gun. This is why automatic and semi-automatic small arms need to have a special adaptor fitted to them when firing blank rounds. Without the adapter the recoil of the blank round is not strong enough to cycle the action.