Stating custom firearms

[Kfireblade]

Originally Posted by johndallman

Got a page reference for that?

I said the wrong thing, have now edited that post. Tactical shooting pg.69

[fula farbrorn]

Does anybody have good advice for using Coles spreadsheet to stat up stuff like 7N39 ?

I tried my hand at it and 12.7x55 but i feel like i am messing up somewhere

[Jinumon]

Originally Posted by elaxter

For a .50 cal revolver I would just use the stats for the Ruger Super Redhawk (RSRh). Reduce the damage by 1 (so it's 5d-2 pi+) to reflect poorer quality propellant (unless this isn't an issue) and change the reload time to whatever seems appropriate. Range is that of the RSRh. RoF should match other TL5 revolvers. ST is definitely 12. Bulk is -3. Stats like weight, cost, max shots, etc. are up to you.

That should have you set.

Yeah, as Fred Brackin said, the performance is gonna be a lot lower than that. The Improved Black Powder of late TL5 is only about 60% as powerful a propellant as the Smokeless Powder/Cordite we use today. Multiplying the RSRh's damage (5d-1 or 16.5 average damage) by 0.6 (3d-1 or about 10 average damage) will get you a lot closer to a realistic starting point, which is also nearly in line with some of the biggest handcannons of the period.

Honestly, I'd probably just take the Colt M1873 SAA and adjust each of its other stats according to the Square-Cube Law based on the proportional increase in bore diameter. That tends to provide half-decent numbers at least.

Jinumon

[Jinumon]

I got bored so I decided to do my own workup for it based on my own above suggestions. Use it or don't.

Custom Handcannon, .50 Custom Long
Damage 3d pi+
Acc 2
Range 130/1,400
Weight 3.8/0.34
RoF 3
ST 13
Bulk -3
Rcl 5
Cost $850 (if manufactured, likely x2-10 that if handmade)
LC 3

Keep in mind the would-be gunslinger is also going to need to be able to press his own ammo, as he's using custom ammunition.

Jinumon

[Fred Brackin]

Originally Posted by Kfireblade

Adesigned for a longer and maybe like, 30%, more powerful cartridge. r.

Where are you going to buy custom cartridges from. The .577 is going to be bad enough but you can probably mail-order them from New York city.

An absolutely original cartridge will have to be made by the PC from the brass up and probably this involves non-portable gear like an annealling oven. Then after he's made all of them he needs he's going to have to carry as many as he needs with him all the time.

I wouldn't want a custom cartridge for any gun I shot regularly. At most I would want to invent a speedloader for a S&W #3.

Also, if you think that the Trantor is less powerful than a.45 Colt you may have misread the damages. The Trantor is 2D+2 P++ for 9 pts of penetration and 18 pts of wounding. The Colt is only 3D-2 P+ for 8.5 pts of penetration and 12 pts of wounding.

[Rupert]

Originally Posted by Jinumon

Yeah, as Fred Brackin said, the performance is gonna be a lot lower than that. The Improved Black Powder of late TL5 is only about 60% as powerful a propellant as the Smokeless Powder/Cordite we use today. Multiplying the RSRh's damage (5d-1 or 16.5 average damage) by 0.6 (3d-1 or about 10 average damage) will get you a lot closer to a realistic starting point, which is also nearly in line with some of the biggest handcannons of the period.
ease in bore diameter. That tends to provide half-decent numbers at least.

Damage, assuming similar bore and bullet, scales as the root of energy in GURPS. Thus the damage should be 16.5 x 0.6^0.5, or about 16.5 x 0.775 = 12.8, for 4d-1 pi+ (a .577" bullet is under 15mm and thus still only does pi+). That's more damage than a 5.56x45mm or 7.62x39mm round, and has a reasonable chance of forcing a death check from a single torso hit, so should be sufficiently scary.

[Kfireblade]

Originally Posted by Rupert

a .577" bullet is under 15mm and thus still only does pi+.

so 15mm is where damage becomes pi++? wasn't ever sure on that exactly where the line was.

Also actually, on the ammunition table in adventure guns it lists .577 revolver as being 15.6 x 20mmR.

[Pursuivant]

The most helpful referenced I've found for GURPS black powder custom guns is here:

http://panoptesv.com/RPGs/Equipment/...lackPowder.php

While you have to convert to standard GURPS dice of damage and possibly convert from metric units to Imperial, it's fairly reliable when designing TL4-5 black powder guns which fire balls.

Things get a bit weird when designing guns which fire Minie balls or BP cartridges, since you have to fiddle with the size of the powder charge, but it's fairly easy to get plausible results.

[Rupert]

Originally Posted by Fred Brackin

An absolutely original cartridge will have to be made by the PC from the brass up and probably this involves non-portable gear like an annealling oven.

Probably not for black-powder rounds, and just tossing them in a cooking fire would do. If the case was simply a large bore rifle case cut down it wouldn't be too hard to make, either (though very expensive for pistol ammo).

I wouldn't want a custom cartridge for any gun I shot regularly. At most I would want to invent a speedloader for a S&W #3.

For the period I like the idea of a Peacemaker in .44-40 with a Winchester M1873 also in .44-40. They use the same ammo with the same loading (unlike modern .44-40 carbines which tend to have loadings to hot for most pistols), and it's a popular and common round and thus supply shouldn't be a problem. 2d+2 pi+ for the pistol and 3d+1 pi+ for the rifle is enough damage for hunting and self-defence in a time and place where body-armour was next to non-existent.

[Rupert]

Originally Posted by Kfireblade

so 15mm is where damage becomes pi++? wasn't ever sure on that exactly where the line was.

I think it's actually 0.40" and 0.60" for pi+ and pi++ respectively, given that these were the thresholds in 3e for the equivalent effects, and .40 S&W does pi+ damage while the .600 Nitro Express does pi++ damage.

So 10.16mm+ and 15.24mm+, to be precise.