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Old 09-27-2017, 05:20 PM   #61
Anthony
 
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Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by mlangsdorf View Post
I stole this from Doug's spreadsheet:
volume in cubic cm = (PI*(Bore/2)^3 + PI/12*Bore^2*(2*Bore*Aspect Ratio-Bore)) / 1000
For a bullet with a perfect half-sphere rounded tip:
Volume of tip = 2/3 * pi * r^3
Volume of cylinder = pi * r^2 * (length - r), or pi * r^3 * (aspect ratio*2 - 1)
where bore is bullet bore in milliimeters and aspect ratio is bullet length / bullet bore.

Accumulating variables, we get pi * r^3 * (AR*2 - 1/3), or pi*B^3*(AR/4 - 1/24).
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Old 09-27-2017, 07:28 PM   #62
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Default Re: GURPS ULTRATECH ballistics?

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Originally Posted by mlangsdorf View Post
For rifle caliber bullets, 3G3 suggests roughly a 3:1:3 ratio of bullet mass to propellant mass to casing mass. A caseless round should weigh about 4/7ths an equivalent cased round - and when you consider that you're really evaluating TL6 cased rounds with moderate REF propellants versus TL8+ caseless rounds with higher REF propellants, you can get half the weight.
Except that caseless propellants need binders, stabilisers, and other additives that cased propellants do not. That's why the propellant weight of the 4.7mm caseless is so high relative to bullet weight.
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Old 09-28-2017, 07:40 AM   #63
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Default Re: GURPS ULTRATECH ballistics?

Quote:
Originally Posted by mlangsdorf View Post
I stole this from Doug's spreadsheet:
volume in cubic cm = (PI*(Bore/2)^3 + PI/12*Bore^2*(2*Bore*Aspect Ratio-Bore)) / 1000

where bore is bullet bore in milliimeters and aspect ratio is bullet length / bullet bore.
what this is supposed to be - and I'm too tired to really check it right now - is a cylindrical base equal to half the bore in height. That's pi x (Bore/2)^2 x Bore/2, which of course is pi x (Bore/2)^3.

Then it adds in an ellipsoid of revolution, volume pi/6 x A^2 x C, and C is the Aspect Ratio x 2 x Bore. And we only need the top half. you get what's in the formula.

It's not perfect by any means, but if you look at the shapes produced, they look pretty close to what real bullets look like, and makes the density measurement not bad.
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Old 10-07-2017, 08:09 AM   #64
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Default Re: GURPS ULTRATECH ballistics?

For those interested in Caseless rounds...

Do a search on Caseless rounds good bad ugly.

There will be a pdf entry listed as:

http://www.forgottenweapons.com/wp-c...Small-Arms.pdf

There, if you read the presentation, near the end of the PDF, you will find some rather eye opening "issues" that included total destruction of the weapon, along with stoppage clearing issues that were estimated at 10 minutes to clear. The 50% round weight estimate seems to be pretty much on the mark according to this - but the pictures showing what happens to cause stoppages included cracked cartridges amongst other things.

The author also mentions that the Brass case cartridge has specific benefits. I would suspect that those interested will look the document up, those not interested, will not. As for myself? It makes me more determined NOT to use caseless round weapons for my cyberpunk campaign.
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Old 06-26-2020, 04:06 AM   #65
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Default Re: GURPS ULTRATECH ballistics?

Way back in 2017 I started a blog post addressing many of the issues mentioned here. Somehow I never got around finishing that even though it was more or less done. I finally posted it.

Cheers

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Old 06-28-2020, 09:58 AM   #66
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Default Re: GURPS ULTRATECH ballistics?

And rather good it is too. Thanks!
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Old 06-28-2020, 02:36 PM   #67
hal
 
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Default Re: GURPS ULTRATECH ballistics?

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Originally Posted by johndallman View Post
And rather good it is too. Thanks!
I liked it as well. It did bring back to mind the fact that the original M-16 round was intended to be specially produced with specific characteristics as evidenced by this quote:

"A drawback of the direct gas impingement system is that, by blowing fired cartridges’ gas directly into the firing chamber, it also blows those cartridges’ residue in there as well, fouling the chamber. Hence, the need for frequent cleaning. The M16 was designed to fire a cartridge that used a specific powder to minimize that problem, but when the US Army discovered that the special powder could not be readily mass produced in 1964, it replaced it with an alternate that produced significantly more fouling."

Maybe the case-less telescoping round will make its debut on the world stage - someday. The change from the 7.62 NATO to 5.56 NATO was not without its hiccups and certainly was not something anyone from World War II time period would have anticipated.
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Old 06-28-2020, 04:41 PM   #68
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Default Re: GURPS ULTRATECH ballistics?

A lot of the issue with improvements to small arms ammunition is that you need a pretty big improvement on existing small arms (I think the target for the last round of proposed replacements was doubling hit chance) for it to be worth the trouble to do anything but a drop-in replacement (ammunition that can be used in legacy guns, or guns that can fire legacy ammunition).
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Old 06-29-2020, 12:00 AM   #69
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Default Re: GURPS ULTRATECH ballistics?

Modern focus has primarily been in different construction material of cases compared to brass.

Polymers are considered useful as construction material due to the fact they're insulators instead of conductors of heat (thus they heat up slower and don't spread heat to the barrel or chamber as quickly as brass cases do) in addition to potentially being lighter and cheaper to make.
https://www.gunsandammo.com/editoria...unition/247607
Quote:
A polymer case is an insulator rather than a conductor. When the cartridge fires, the case contains the heat and pressure and directs it all down the barrel. Instead of super-heating brass that then heats the chamber around it, the only heat the entire barrel sees is what's found in the bore. Heat will certainly move from the barrel around the bore back into the chamber area, but keeping the heat out initially will reduce how quickly the AR bolt heats up, thereby prolonging its life. The way this ammunition manages heat should appeal to military and high-volume shooters alike.
https://www.thefirearmblog.com/blog/...d-50-cal-ammo/
Quote:
MAC, LLC, the Mississippi-based lightweight polymer tech specialists, have won a $10 million indefinite delivery-indefinite quantity contract to provide the US Marine Corps with uptp 2.4 million rounds of hybrid polymer/brass-cased .50 calibre ammunition. The contract will allow the USMC to evaluate the new ammunition in user trials

MAC, LLC describe themselves as “a technology-based company focusing on development and commercialization of lightweight, polymer-based solutions for military and aerospace markets.” In 2018, we reported the NAMMO, the Nordic munitions and defense corporation, had acquired MAC but the USMC contract is in MAC’s name, not their parent company NAMMO’s.

The USMC have been interested in polymer for a number of years, culminating in a sole source solicitation for .50 cal polymer cased ammunition. The $10 million award to MAC answers this requirement.

Last edited by warellis; 06-29-2020 at 12:08 AM.
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Old 07-14-2020, 11:38 AM   #70
hal
 
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Default Re: GURPS ULTRATECH ballistics?

Just stumbled across this video on youtube - included the link here just for those who might be curious. Don't know how accurate the material is, but it is interesting to say the least as it goes into the history of the G11 history from 1967 onwards.

Youtube Link

You get to see the entirety of the weapon system as it is broken down. You get to see what a 50 round magazine/Clip looks like, and you even get to see how the gun carries a total of 150 rounds (50 ready to fire, and two magazines each holding 50 rounds, one to the left and one to the right of the central magazine that feeds the gun itself. So no, not 150 rounds, just 50, with two reloads carried on the gun itself.

The model is the G11-K2 in the video, which was shot on location in Virginia. Hope you enjoy it as much as I did.

What surprised me is just how long this weapon system has been in development. I did enjoy seeing the gun stripped down to its component parts and the explanation of how the three shot burst system was intended to work.
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