It's A System

I got GURPS: Gun Stats in January, I didn't do much with it except notice that the formulas don't recreate the, already, published stats for the M1 Garand.

An M1, in GURPS: High Tech, does 7d+1 pi out to 1,100/4,500, as does the Winchester Model 70.

So, armed with real world numbers for Cartridge, .30 caliber, M2 Ball, I dutifully plugged information into the formula and got:

7d+1 pi (so far so good) out to 890/3,700 (whups).

So I did .270 Winchester, which, according to Pulp Guns Vol. 2 stats for the Winchester Model 54, should do 7d pi out to 900/3,600.

The formula says: 7d+1 pi to 1,150/4,800.

Then I remembered that M2 ball's pressure curve is atypical of .30-06 and plugged in the numbers for Remington 150gr Core-Lokt.

7d+1 pi out to 1,020/4,300.  That's a lot closer to the published stats than what using the M2 ball figures gets you.

So I moved on to the AR.

An M16A1 (High Tech) firing M193 ball gets 5d pi; 500/3,200.  Gun Stats calculates it as 5d pi; 440/3,100.  Close.

An XM177E2 (SEALs in Vietnam) firing M193 gets 4d+1 pi; 420/2,700.  Gun Stats calculates it as 4d+1 pi; 370/2,600.  Also close.

An M16A2 (High Tech) firing M855 ball gets 5d; 800/3,500.  Gun Stats gives 5d pi; 460/3,200.

An M4 (High Tech) firing M855 ball gets 4d+2 pi; 750/2,900.  Gun Stats gives 4d+2 pi; 430/3,000.

So far the damages have been about right, but ranges differ greatly from published weapons.

But what really clonked me was calculating .30-40 Krag.

Adventure guns says the M1892 rifle does 6d+1 pi; 1,000/3,900.  Gun Stats says 6d pi; 1,030/4,300.  A round nose 220gr bullet at 2,000 fps outdistances a 152gr spitzer at 2,800 fps.  Also notice, except for the damage, that it calculates nearly the same ranges as a modern .30-06 load!

Spain's 173gr 7x57mm loading comes to 6d+1 pi to 1,190/5,000 so the Spanish Hornet still outranges the boys on Kettle Hill.

.30 Carbine takes a big hit, going from 4d+1 pi; 330/2,100 to 4d pi-; 290/3,200.

Which brings us to the Big Huge Question™:  With the disparity between published and calculated stats: do you use the calculated stats for unpublished weapons alongside the published weapons, or do you recalculate ALL the published ones?

Especially considering that the Douglas Cole calculations and Vehicles for 3rd Edition come much closer to the published stats.