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Cool Guns for your Games


Remjin
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3 hours ago, Sundog said:

 Actually, I think the one Ian's using is good. Normal troops want to stay well away from supers.

 

Probably how troops without AT weapons handle enemy tanks, which is hide, give accurate reports on type and position to their superiors, and wait until it goes away, or until the superiors plan kicks off and the enemy tank blows up.  

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Yep, the "best" way to fight a super is by sniper fire. And laser designation for bigger ordinance. But we are right about having exoframes in real life, so in a "super" world the should have armored exoframes with .50 as the standard, and a 20mm auto cannon for larger targets with missile/drone support as well.

 

I think the first use for a bullpup .50 is for special op units as a sniper tool.

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On 11/29/2016 at 11:26 PM, Cancer said:

Ok ... the 7.62 mm NATO cartridge seems to have 46 grains = 2.98 grams of ball propellant. That propellant has a variety of compositions, but for the sake of prgress (based on numbers I could find) I guessed that the total energy release is about 0.7 times that 3 grams times the heat of combustion of nitroglycerin, and that product is roughly 14,000 Joules for the discharge of one round.

 

For a 9.5 gram bullet at muzzle velocity of 800 meters per second, the KE of the bullet is a bit over 3000 J, which is a bigger fraction of the propellant energy than I would have guessed.

 

But assuming that most of the rest of the propellant energy is heat taken up by the mechanism, that'll be in the neighborhood of 10,000 J per shot.

 

The heat capacity of steel at room temperature is about 455 J per degree C per kilogram, and I could not find the mass of the steel parts in an M14 rifle (I found those for sale at several webplaces, but they didn't list the weight). Hopefully folks here can provide that information. Merely to make progress, though, if the working mechanism is 1 kg of steel, and all that heat stays in the steel and it equilibrates, then at the end of it, the steel is warmer by about 22 degrees C.

 

The heat capacity of steel goes up slowly with temperature; it's about 50% bigger at 1000 degrees C, which doesn't matter much for this exercise.

 

Put a different way: if this is in the right ball park, then firing 7.62mm NATO at the rate of one 20-round clip per minute means you've got roughly a 33 kilowatt heater in your hands as you fire. That tells you the magnitude of the coolant system you'd need to have in the weapon for sustained operation.

 

Resurrecting a long-dead post, I blundered on a relevant reference for this sort of question (while I was trying to come up with a problem for my freshman mechanics final exam :fear:).

 

For a typical modern firearm, the energy from the propellant gets partitioned remarkably close to equally into three bins, with a small (couple of percent) overall loss.  The three bins are (1) bullet KE; (2) heating the mechanism; (3) energy remaining in the expelled gas (heat, KE of the gases, muzzle flash, sound, ...).  A couple of percent goes into friction of bullet in the barrel and a tiny amount of propellant gets expelled rather than burned. 

 

So ... I overestimated the heating in the mechanism by about a factor of 2, since I completely neglected heat in the expelled gas.  Call it astrophysical accuracy.  :rolleyes:

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On 2/14/2022 at 1:42 PM, Christopher R Taylor said:

3 seconds per shot isn't awful, and this is just beginning.  That is a pretty heinous EM field though, that could kill your watch, for example.  And that amperage!!!  I know its seriously subsonic and fairly low power but the sound is quite disappointing as well

 

The EM pulse ... frankly, I'd wouldn't want to have a helmet radio when using that.  Would be interesting to put it on a tabletop, one scattered with staples, straight pins, BBs, or whatnot, and see how those respond during weapon discharge.

 

Also wonder about the weapon's signature in the infrared (since this seems like a night weapon to me) once it gets warm.  But, all that's future considerations.

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On 3/14/2022 at 1:53 AM, Cancer said:

 

The EM pulse ... frankly, I'd wouldn't want to have a helmet radio when using that.  Would be interesting to put it on a tabletop, one scattered with staples, straight pins, BBs, or whatnot, and see how those respond during weapon discharge.

 

Also wonder about the weapon's signature in the infrared (since this seems like a night weapon to me) once it gets warm.  But, all that's future considerations.

Having worked a little with modern capacitors, heat bleed is a thing. If you're going to charge them more than once you're going to get a distinctive heat signature.

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On 4/25/2022 at 3:11 PM, pinecone said:

Well, the Army in it's vast wisdom has chosen the Sig, with the 6.8 x51. So it seems that they went with "Battle Rifle" as x51 is not an intermediate size. Not supposed to be super heavy though....

They want the range of a full-power cartridge while keeping the capacity to carry a reasonable quantity of ammo. Plus, I think the ability to base a light MG off the same platform, with all the advantages that gives for logistics, kicked the SIg bid over the line.

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My understanding is that the military really doesn't care about body armour. Since any actual hit (as opposed to a ricochet or spall) from a rifle will punch straight through any body armour currently available. What's bothered them was the inability of current gen assault rifles to reach targets at long ranges, especially with carbines like the M4.

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On 5/1/2022 at 7:26 AM, Christopher R Taylor said:

I am unsure that there's a need to be fighting beyond a certain range, since after a while you need specialty shooting to be accurate or useful anyway, but whatever.

Army felt the same way. But in Afghanistan they had a number of cases of insurgents using older, full-power rifles being able to engage US troops at ranges where AR-15 based weapons couldn't effectively reply. This was especially the case with troops issued the M4 Carbine, but it also happened with full-length variants.

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