GURPS ULTRATECH ballistics?

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Originally Posted by Fred Brackin

Ammo weights might be the most hashed up numbers in UT. I doubt you can do anything sensible with them.

Hi Fred - at the risk of engaging in thread necromancy here, I took a fresh look at the data, trying to find ways to maybe use HIGH TECH guns repurposed to a TL 9 standard instead of TL 8 standard.

One thing you stated above just got confirmed.

Looking at the real world data on the Rifle round for the G11 4.73x33mm round, the weight of the bullet is 3.1 grams (49 grains) and the weight of the round is 12.05 grams (186 grains). That produced a round velocity of 3051 feet per second or 930 meters per second.

So, I did a look up on how many grains to the pound as well as how many grams per grain.

There being 7000 grains to the pound, we can switch between real world measures of bullets and rounds when talking about ULTRATECH rounds as given in the 4e version of Ultratech. Thought you and others might find it interesting...

Multiply the WPS on page 139 by 7000, and that gives you the number of grains per round in weight. For reference, the G11 round was 186 grains, or would weigh roughly .027 lbs per round. High Tech says .011 lbs per round, so there is something of a discrepancy there. Could be simply difference references (I used THE GREENHILL MILITARY SMALL ARMS DATA BOOK by Ian V. Hogg in this instance, published 1999).

Using the formulas outlined above...

		WPS	Grains
7.5mm		0.006	42			
10mm		0.014	98			
15mm		0.06	420			
						
5.7mm		0.013	91
7mm		0.027	189
10mm		0.04	280
10mmCLR		0.06	420
15mm		0.2	1400

If roughly 25 to 26% of the round weight is the bullet weight (just an assumption based on the 1:2.89 ratio for the G11 round) then we can arrive at some values based on the numbers given in ULTRATECH.