Re: TL4 to TL5 Cannons and Carronades
 

Agreed on both. Also should a question arise about real-world effects, since the fundamental starting point, and point of compatibility, was pre-existing GURPS stats. Those might well be accurate, or they might not. Regardless, Doug's spreadsheet isn't meant to be a physical simulation of kinetic energy penetrators from first principles.

Re: TL4 to TL5 Cannons and Carronades
 

If you're interested in that, Luke Campbell poked at that.

Re: TL4 to TL5 Cannons and Carronades
 

Does anyone have an idea about what factors in Doug's calculations specifically account for rifling and/or nitrocelluse propellants?

Or what to change when modelling smoothbores and an equivalent to black powder?

In any case, Doug's spreadsheet produces results that appear to be in the ballpark for High-Tech's black-power, smoothbore muzzleloading personal firearms of .45 caliber to 8-bore. If anything, Doug's spreadsheet is slightly less optimistic in terms of Max Range (and more optimistic in terms of 1/2D Range), but still within an acceptable margin of error from the published stats when I input what muzzle velocities I can find, a few from period sources, but mainly from reenactor and amateur black powder shooter sources.

It's when I get to cannon that the stats generated by the spreadsheet and the published ones stop being in the same ballpark. To some extent, of course, Low-Tech might be assuming very low velocities for its cannon, due to inferior powder, but as noted above, even the TL5 12-pounder Napoleon gets a significantly higher Dmg (6dx7 pi++) in the spreadsheet than is actually the fact in High-Tech (6dx5 pi++).

As far as I can determine, Doug's formula accounts for the diameter of the projectile and aspect ratio 1 of a round ball, and thus the comparatively larger impact area than if it were a conical ball or spitzer bullet.

Is there some other factor that makes larger and heavier round balls exhibit less of a gain in penetration than one would naively assume?

I remember that by the standard GURPS damage equation, going from .600 NE to .700 NE didn't really produce much of a performance increase. I think Hans explained it as the increase in bullet cross-section almost counteracting the higher energy. Could this be a similar issue?

Re: TL4 to TL5 Cannons and Carronades
 

In some campaigns I might just ignore the game stats, and focus on understanding the real properties of similar weapons, on the grounds that the result when a human being is shot with a cannon is "they lose whatever body part it hits" and the GURPS damage rules are not the best for simulating damage to large ships or fortifications. If I already know more or less what will happen when my galleon gives fire to those nasty English sea-dogs, no need to convert the gun side and the target side into game stats!

But the Realms have giant monsters, heroes who can take more damage than ten men, and magical armour ... so damage could be a useful stat.

Re: TL4 to TL5 Cannons and Carronades
 

Indeed. I've avoided using the RAW damage vs. HP mechanism when attacking large wooden vessels. Archers and slingers, no matter how many, are not going to destroy typical warships in a minute or two of missile fire.*

I generally just count each part of a ship as a seperate wooden structure, with DR and HP according to thickness, with maybe a slight boost to DR for the shape of the hull of later warships. Actual line of battle ships ought to rate at least DR 30 at their strongest points, not only because 2+ feet of oak are that strong, but also for there to be any need for heavier cannon, as otherwise anything higher than 3-lb will simply blow through.

Penetrating the DR and 1/4 of the HP gets through the hull, with effects varying.

*Incidentally, the DR for wooden warships is strangely low in GURPS, when compared to the stats of wooden walls. I can't really explain why the 18" oak bulkheads of a frigage should be DR 6 in GURPS, but as soon as you remove the ship and make it simply an 18" thick wall of oak, the DR triples.

Just so.

DR 30, HP 300 dragons call for pretty big swivel-guns to handle air defence.

Re: TL4 to TL5 Cannons and Carronades
 

If it helps, I'll see if I can dig up the following information for age of Napoleon cannons as far as shot diameter, shot weight, as well as powder weight and muzzle velocity. Chances are good that when you run the numbers, they won't match published GURPS values.

With powder weight, it should be possible to determine how efficient the powder burned to get muzzle velocity.

Re: TL4 to TL5 Cannons and Carronades
 

I would enjoy that.

I'm reading an excellent summary called British Smoothbore Artillery: A Technological Study to Support Identification, Acquisition, Restoration, Reproduction, and Interpretation of Artillery at National Historic Parks in Canada by David O'Connel*, which is excellent for the dimensions and weights of the guns, but I welcome as much data I can get on muzzle velocities, powder charges and suchlike.

*Obviously a man who felt titles should be very descriptive.

Artillery through the Ages:
 

http://rnzaa.org.nz/sites/all/files/...the%20Ages.pdf

. . . is a good easy-read primer on the subject; includes descriptions of guns (including odd names such as saker & minion) with bore diameters & lengths of barrels.

Should allow you to design same (or close to it) with GURPS Vehicles 3rd or its successor.

Re: TL4 to TL5 Cannons and Carronades
 

Icelander, you may find this useful: http://arc.id.au/CannonBallistics.html

Re: TL4 to TL5 Cannons and Carronades
 

Yeah, that is pretty awesome.

Thanks.