Wait you mean the History Channel was showing something about History? Who let that happen? Was there at least a mention of Space Alien Nazis?
This is something I know quite a bit about, I'm a ballistics technician at a leading ammo manufacturer. 1) a round projectile needs a slow twist, when I build muzzle loaders that shoot round ball its a 1:66 twist or 1 full turn in 66" of bbl length. A .308 usually has a rate of 1:10 for comparison. It has to do with the amount of bearing surface and length/ weight of the projectile. 2) a projectile needs to obturate or expand to engage the rifling, when I worked on naval guns we put a nylon band that would engage the rifling. A bb would need either a nylon coating or pressures in excess of 15kpsi, most handgun loads run 16-30kpsi depending on caliber and rifles are more like 50+kpsi. The rifling in Daisy and other air guns is strictly for shooting lead pellets that have a thin skirt that expands to engage the rifling. Just some basic info from someone who has sniffed way too much burnt propellant. Brian
I think you are missing the point. The twist rate is what is key here. A 1:66 twist for a round ball muzzle loader says that for the rifling to turn once inside the barrel takes 66" of length. Your barrel will be 3-5" for a straight barrel and 5-7" for a bent barrel. There is not enough barrel length to put a proper spin on the BB to stabilize it, and you will likely see shots go consistently off to one side because of it. You would need a very high twist rate to make this work due to our extremely short barrel lengths, and high twist rates don't work well with round projectiles. So you are better off without the rifling.
Nope, the twist rate stays the same despite bbl length, it will impart the needed spin rate. An example is the any current handgun say in 38 spl for example, all revolver have the same twist rate despite having bbl lengths from 2" up to 8". I have two muzzle loaders that are designed to shoot .54 cal round ball with 1:66 twist rates the rifle has a bbl length of 42" and my pistol has a bbl of 12". The rate of twist stays the same despite the length of the bbl. It would be possible to rifle our guns but the pressure needed to engage the rifling would far exceed our safety margins.a coating of some sort could be used to engage the rifling ala the patching used in muzzle loaders, but i don't think the gain in possible accy would off set the cost of development or manufacturing.
Actually added accuracy would be outstanding for Big Gun as mentioned before accuracy at range would be awesome. Due to the mandatory pause between firings you wouldn't hit the same spot but also at range the idea would be to just hit the other ship and do some damage to gain points. Like Brian said the cost will probably outway any gain but it would be a cool thing to show off none the less. Brian, given how our magazines work do you have any ideas as to a type of coating that would work if one were to make some rifled barrels for testing purposes?
As I said earlier, there is no need for rifling in a standard big gun cannon as the curved barrel imparts spin to the balls anyway.
I'm not sure because the pressures we work with in our ships guns are so small that they aren't even considered noise in a standard ballistics test. It would need to be soft enough to engage the rifling but hard enough not to shred as it travels down the bore, then it would also have to adhere to the projectile when it leaves the bbl or it would affect any accuracy gained by changing the spin rate and direction. I know we are currently testing some powder coated bullets as a possible replacement for copper jackets and we have sold nylon clad ones since sometime in the '80s. The nylon leaves some bbl fouling so the bbl's would need to be cleaned after firing, adding yet more to between battle maintenance. Not trying to be a wet blanket on the idea but I want to give you some idea of whats involved. Ballistics is all about variable control, that's why most times projectiles don't hit in the exact same location each time. A really good read for understanding some of what would be involved is a book called "Understanding Ballistics" by a guy named Kinkor, you can get it at Cabelas, and probably Amazon. It allows you to go as deep into the subject as you are comfortable with, from a basic surface understanding all the way to the higher math and physics involved with anything from BB guns to artillery pieces.
All this talk about rifling and increased accuracy is a mute point in warship combat. All the accuracy in the world isn't going to give a damn bit of an advantage until the problem of a stable, well aimed fire-control platform is addressed. Some in the tank hobby obsessed with long range sniping go to extreme lengths to get one shot hits on target. Micro-millimeter accurate rotate and elevate systems are built, coaxial targeting lasers and cameras are mounted, and the operators are standing RIGHT BEHIND their cannons for aiming. All this, and it's still blind luck if somebody gets one shot one hit. It typically takes several rounds and a good eye to hit long range. All the while the sniper is fixated on his long range gunnery, I'll swing around and take him out from 5'. I don't see how any of this will translate to warships (lasers, cameras, etc) under any current rule set.
The point of increased "accuracy" is more along the lines of being able to engage at longer ranges such as when ships are closing for combat. Wouldn't the ship closing who can start landing shots earlier have a distinct advantage in scoring?
Sure they would but tight patterns at long range require a lot more than the rifling under discussion. The point I was trying to make earlier was that you need a solid foundation and sighting to shoot accurate. A sniper has his tripod, scope, and steady nerves to get one shot kills. Model warships, especially big-gun boats have none of these. I twitch of a rudder, a wake, or the wind can push the boat over and there goes your firing solution. Many big-gun boats have basic on/off left/right rotate with no feedback as to where the guns are pointing, the operator has to determine this by site from shore. Also, there may be an elevate which might be a servo pushing the barrels up and down but where exactly was that servo set? The captain has to remember/determine all this in the heat of battle. Big gun barrels are not tight tolerance (to accommodate that bend) which makes them inherently sloppy. Multi-gun designs that I've seen WILL NOT vent the same pressure to each barrel so you will have different ballistics on each barrel. The nuts to crack IMO for model warship big-gun accuracy are a stabilized shooting platform (or compensating elevate mechanisms) and operator feedback on turret angels (or preset angles). Camera and laser sighting systems have yet to prove themselves in tank combat and I doubt they'd do any better on the water at our scales. I'm not saying that a boat and gun system couldn't be developed that could hit a bullseye from across the pond, but I'll bet that builder will miss a ton of time (and fun) on the pond doing so. If someone wants to put time and effort into big-gun to such a degree, they should but that effort into making an off-the-shelf affordable cannon. That would do more for the hobby than rifling.
Steve has really nailed some of the mechanical slop inherent in big gun cannons. You were asking on Ben's Drydock how to improve Impero's cannon mounts to be both more stable and provide easier access to cannons for maintenance. That will probably improve your accuracy more than rifling will, and the easier access will be even more important. I have some combat footage that is worth taking a look at. In July 2010 I mounted a GoPro RC Hero on Ben's Rodney, then posted the raw footage on youtube. In August, I put it on my Tegetthoff, and put together a short video of the recording. There is a lot of info that can be gleaned from the footage. First off, the videos: Rodney part 1, Rodney part 2, Tegetthoff compilation. In the first two videos with Rodney, you can see that Ben was on convoy escort duty. You can see some medium range skirmishing along with a few close encounters with marauding cruisers. I noticed some human error: Ben likes to depress the guns when the target is too far away, and sometimes doesn't line up the shot very well. You can also see the size of the targets at a distance compared to up close. The rocking of the ship isn't too bad, but adds another element of uncertainty when aiming. The video with Tegetthoff shows some up-close knife fighting between myself and Randy's SoDak. The key part is between 1:30 and 1:55, when SoDak delivers the killing blows only a couple minutes after the battle started. This shows how big the target is up close, so aiming is less important than ranging when closer than a foot. I literally pointed my gun about 90 degrees of the bow and fired when the range was right. Closer ranges also mean a greater down-angle, so your shots pass through less water, losing less energy before hitting balsa. By the same principle, the balsa is effectively thicker, like sloped armor on a tank, so I don't know how much that affects penetration. You can also see the difference in penetrating power between 7/32" and 1/4". I had eight belows, he had none. I digress. The low perspective, wide angle, and low resolution make it difficult to maintain situational awareness or identify distant targets if a person were battling with the video feed. Perhaps mount both a wide angle and a narrow FOV camera up on the superstructure, and use a video switcher? Again, I digress. What was I trying to say? Scoring hits at long range is a cool feat, and scores some points, but victory generally goes to the ship that gets in close and scores belows. Become a master at that range, and you'll be a fearsome opponent.
I'm very much on the "it's a complete waste of time" side of this discussion, but (just for fun).... What if instead of metal bb's, you fired those plastic "airsoft" type bb's? They're slightly larger diameter, meaning they will engage rifling in the barrel of a .177. OTOH, I don't think any pond owner would be very happy having a couple hundred of them floating around after a battle. Oh, well.
Gascan, I am not disputing that the close range belows are the true path to victory. The point of this thread was more a whacky idea of comparing our cannons to the historical ones that eventually were rifled along with essentially a what would happen question. I feel like a lot of the things in this hobby started out the same way. hehe I promise when I get out in how ever many years I will try to experiment with this, just for fun, to see what exactly will happen because all the talk in the world is just that until someone does it right?
I hope I wasn't getting too passionate in my response. I watched those videos for the first time in forever and saw some really interesting stuff, which may have made me get a little excited to share it. I see where you're coming from now. On that same path, I would love to put some of my FPV gear on a battleship, either as a gunner or (later) full captain. I know that there are some airsoft pellets that are biodegradable, so having a bunch floating on the pond afterward won't be much of a problem for long. I thought airsoft guns used a hop up to apply a backspin to increase range and accuracy, rather than rifling. If rifling were really effective for airsoft, I'm sure someone would have done it by now.
I've done some "experimenting" with the airsoft pellets and rifling. A friend of mine and myself loaded some pellets into 6mm Remington cases, no powder just the primer, and fired them through his bolt action rifle. We caught them on high speed video exploding about a foot from the muzzle. I believe it was a combination of the "cutting" of the projectile by the rifling combined with too fast of a twist rate that caused them to basically explode. It was pretty damn cool looking though. I would post the video but its on the computer that decided to eat its own hard drive. Hmm now that I think about it, that computer would make a really nice target next time I head out to the range, yeah "Mr Dell say hello to my little friend!" Yes most air soft guns put backspin on the round to give it some accuracy out of the sloppy smooth bore barrels they come with. They can be pretty accurate though, I have the welts to prove that from tactical training that I've done. Steve hit the main accuracy issue right on the head though, with it being the platform itself. With my background as a ballistics tech, gunsmith and former competitive shooter, nothing drives me crazy like the fact that the stern guns on my cruiser can only make decent groups around a foot or so away, not a range that I'm used to shooting at. All that being said, I think there is some tech out there that will eventually allow us to engage at greater distances but that will also lead to less places we can battle as we would need larger ponds.
Might be more useful for the more stable shore batteries that some clubs used to use (or do they still)?
