How do you calculate the RCL of a firearm?

[gregoriomata]

For an upcoming campaign I'm going to run, I want to expand the number of firearms available, and with respect to the calculation of the damage and range, I use the spreadsheet that Douglas Cole made ​​available to us in a previous thread (now I can not find the link, sorry), but there are some statistics that I do not know how to calculate. One is the Rcl, the dispersion of the bullets when impacting on the target.
I know the Rcl should be higher the heavier the projectile and the higher its speed, and I think that, for the same caliber, should be less the heavier the gun, right? But is there any formula to calculate this, even approximately? Does it depend more of the kinetic energy (mass times velocity squared), or the moment of inertia (mass times velocity)? How many ounces more a gun should weigh for your Rcl get off a point?
I would really appreciate an answer to these questions.
Greetings.

[whswhs]

Originally Posted by gregoriomata

For an upcoming campaign I'm going to run, I want to expand the number of firearms available, and with respect to the calculation of the damage and range, I use the spreadsheet that Douglas Cole made ​​available to us in a previous thread (now I can not find the link, sorry), but there are some statistics that I do not know how to calculate. One is the Rcl, the dispersion of the bullets when impacting on the target.
I know the Rcl should be higher the heavier the projectile and the higher its speed, and I think that, for the same caliber, should be less the heavier the gun, right? But is there any formula to calculate this, even approximately? Does it depend more of the kinetic energy (mass times velocity squared), or the moment of inertia (mass times velocity)? How many ounces more a gun should weigh for your Rcl get off a point?
I would really appreciate an answer to these questions.

David Pulver has a tentative formula for this, but I don't recall it. However, in terms of physics, recoil depends on the kinetic energy of the gun, not of the bullet. Conservation of momentum gives you mv = MV, so V = mv/M. Kinetic energy is MVV/2, which is (MV)(V)/2, which is (mv)(mv/M)/2, which rearranged as (mvv/2)(m/M)—that is, you take the kinetic energy of the bullet and multiply by the ratio of the bullet's mass to the gun's.

I imagine that with a statistical calculator, or a spreadsheet, you could fit a regression line to the variables and estimate an appropriate constant.

Bill Stoddard

[Kromm]

Rcl measures dispersion of shot during rapid fire. It takes into account true recoil, felt recoil, mechanical inaccuracy, and other factors. Very roughly, it goes up with damage but down with weapon weight, and can be seriously mitigated by recuperation mechanisms or worsened by poor ergonomics. Until we publish design rules, you could do far worse than to scale it with damage, with a minimum value of 1 and a minimum increase of +1 if damage goes up. For instance, if you soup up some 2d, Rcl 2 pistol to 2d+2, it'll end up at Rcl 3. That's extremely rough, but it ought to do.

[Fred Brackin]

Originally Posted by Kromm

For instance, if you soup up some 2d, Rcl 2 pistol to 2d+2, it'll end up at Rcl 3. That's extremely rough, but it ought to do.

These particular numbers aren't going to be that compatible with existing examples of guns. I know Kromm just pulled numbers out of the air to make an example but for a game that mixes pulblished guns and homebrew guns you'd probably want to study the existing examples pretty closely.

My own familiarity with worked examples tells me that Rcl doesn't go up quite that quickly.

Speaking of existing examples, do you have High Tech? If so what about the two Pulp Guns pdfs? Then there's more guns in Tactical Shooting too. There are a lot of guns in those books.

Making new guns in Gurps that are statistically individual in a significant manner is actually pretty hard. Gurps measures gun caabilities broadly and I forget how many times I've seen threads saying "What are the stats for this gun?" when the gun in question then turns out to be 9mm or 5.56 NATO.

The answer in those cases is almost always "Use the weight, cost and number of shots from your Real World sources. Uses all other stats from a common gun in the same caliber and barrel length.".

If you go through the text passsages of HT you're extremely likely to find some weapon that's almost identical for Gurps puirposes anyway.