The general firearms thread!

[Walsingham]

Could maybe just replace his rifle with a shotgun, and leave the sights on? Sounds like he wouldn't notice.

[JFSOCC]

http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

[Azdeus]

http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

 

I've fallen prey to that myself, so, so many times. I'm glad I don't take after my father in that aspect and can accept being wrong when I am.

 

 

It's so much better than the FA-MAS its' not even funny

 

 

 

 

Can you really blame me for not recognizing that it was anything but a modded FAMAS?

 

That said, the FAMAS is a wicked cool looking rifle, as **** as it may be.

Edited September 28, 2013 by Azdeus

[Walsingham]

http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

 

That is interesting. I know from studying composition skills of novices that an inability to perceive and correct mistakes more or less defines them.

[Woldan]

Today I calculated the flight path of my pet load for my precision rifle, converted it to 1/4 MOA clicks (which is the adjustment range of my scope) and made a small chart which I then glued into the scope cover of my rifle. Now If I want to shoot at various distances I simply look at the chart which is just 3 cm above the reticle, dial in the elevation in clicks and I'm good to go. I don't need to make time consuming calculations or give up my shooting position. 
I also added the 150 meters zero so i can zero it back to min range.

 

That chart is EXTREMELY helpful, though its a little off when the weather conditions change, this chart was calculated with 15 degree Celsius and 50% humidity in mind, the bullet drops less in warmer, drier weather. But the difference wouldn't be so big I'd miss the target . Real pros would make charts for winter and summer and switch them out accordingly, but I'm too lazy for that. 

 

Range left, elevation clicks right, with two special indication marks for one+ and three+ complete turns of the elevation turret to avoid confusion. 

 

Edited October 11, 2013 by Woldan

[ShadySands]

You guys make me really miss my rifle

 

The wife and her friend have been asking to go to the range again so maybe I'll get a little hands on time with whatever rifles they have available. I might even find something I like that I'm allowed to own

[Woldan]

What happened to your rifle?

[ShadySands]

the military wouldn't let me keep it and I was going to buy a replacement but I got a job offer in NYC so there was no point

[Woldan]

Whats holding you back from buying a cool rifle in NYC? Yeah, as far as I know the laws are very restrictive there but you can still own surplus rifles which are fun and very effective in the hands of a skilled marksman. Or start with long range shooting with precision rifles?

[ShadySands]

I wanted an AR-15 to replace my M16 and they are not allowed at all and I'd the range situation is weird there. That on top of all the hoops you have to jump through made me abandon the idea while I lived there

 

Then I moved to Denver and while it's not nearly as bad here but AR-15's are still not allowed within the city/county limits. 

[Walsingham]

My considered opinion is that instead of a range table I would entirely empty the scope, and fill it with that weird but delicious red licorice.

[licketysplit]

I've no interest in guns as mechanical things. I used to hunt, enjoyed the ritual if not the actual killing bit. 

[Walsingham]

I've no interest in guns as mechanical things. I used to hunt, enjoyed the ritual if not the actual killing bit. 

 

Do you like other machines, then?

[licketysplit]

 

I've no interest in guns as mechanical things. I used to hunt, enjoyed the ritual if not the actual killing bit. 

 

Do you like other machines, then?

 

 

Just these:

 

Edited October 12, 2013 by licketysplit

[Walsingham]

Hey, Woldan! Your special skills required.

 

 

I believe I've already lost this bet, because I was talking arse generally. But I'd still like the correct answer.

 

This fellah was sounding off about the energy in a can of drink. For the sake of argument, say 300kj. His comment was "That's more than it takes to fire a gun"

 

My immediate response was to say that he was talking balls.

 

I'd like to know how much energy is actually in the propellant for a 7.62x39 FMJ, and (for the sake of interest) in a .50 cal desert eagle round.

 

I am assuming that this is NOT the same as the muzzle energy. Although I would not be surprised if it was.

[Woldan]

Hey, Woldan! Your special skills required.

 

 

I believe I've already lost this bet, because I was talking arse generally. But I'd still like the correct answer.

 

This fellah was sounding off about the energy in a can of drink. For the sake of argument, say 300kj. His comment was "That's more than it takes to fire a gun"

 

My immediate response was to say that he was talking balls.

 

I'd like to know how much energy is actually in the propellant for a 7.62x39 FMJ, and (for the sake of interest) in a .50 cal desert eagle round.

 

I am assuming that this is NOT the same as the muzzle energy. Although I would not be surprised if it was.

Thats quite an...unusual question; I can calculate the muzzle energy of those rounds in joules, but would that be the same joules as in food joules? Thats the question....

Any physicists here?   

 

Lets pretend they're the same unit (I just hope I don't embarrass myself here)

 

7.62 x39 = 125 grains @ 2400 fps = 1598 ft/lbs = 2166 Joules = 2.16 Kj

.50 AE = 300 grains @ 1550 fps = 1600 ft/lbs = 2200 Joules = 2.20 Kj

 

Thats WAY less than 300 KJ, even with a 20x110mm anti aircraft machinecannon round you only get about 57 KJ, 300 would probably be the energy of a main battle tank round. 

 

If its about the energy the powder charge itself contains, well, I have no freaking idea. The problem is powder varies a lot, you'd have to specify what powder is being used in that round. Its impossible to say.

 

In a nutshell: Wals, stop making ridiculous bets while being high on absinthe.

Edited October 18, 2013 by Woldan

[Walsingham]

The guy quoted the energy as being roughly 1.7kj. To which I scoffed. I simply refuse to believe that the energy consumed to throw a bullet hundreds of metres is that small. If so I've probably eaten more energy than was fired off in WW2!

[Woldan]

Wait a second, my ballistics program shows me the specific explosion temperature in KJ per Kg of powder, that would be what you're looking for I guess.

 

For example, lets take Lovex S060 stick powder which is used in a lot of 7.62x39 rounds, it has a specific expl. temp. of 3880 KJ / Kg.

 

1 Kilogram = 15432 grains. Therefore one grain of powder creates 0,25 KJ of energy. A 7.62x39 round would be loaded with approx. 30 grains of that powder, thats 7,5 KJ. Still way short of 300 Kj.

 

Even a .50 BMG round which contains 180 grains of powder with a similar energy would only give you about 45KJ. 300KJ would probably the equivalent of the powder charge of one of the 30mm rounds the GAU-8 fires.

 

Thats very interesting.

 

Though I still don't know if the guy simply means the muzzle energy of a rifle round or the energy the powder charge itself contains. You know, the heat it creates when it burns in KJ.

Edited October 18, 2013 by Woldan

[kgambit]

 

Hey, Woldan! Your special skills required.

 

 

I believe I've already lost this bet, because I was talking arse generally. But I'd still like the correct answer.

 

This fellah was sounding off about the energy in a can of drink. For the sake of argument, say 300kj. His comment was "That's more than it takes to fire a gun"

 

My immediate response was to say that he was talking balls.

 

I'd like to know how much energy is actually in the propellant for a 7.62x39 FMJ, and (for the sake of interest) in a .50 cal desert eagle round.

 

I am assuming that this is NOT the same as the muzzle energy. Although I would not be surprised if it was.

Thats quite an...unusual question; I can calculate the muzzle energy of those rounds in joules, but would that be the same joules as in food joules? Thats the question....

Any physicists here?   

 

Lets pretend they're the same unit (I just hope I don't embarrass myself here)

 

7.62 x39 = 125 grains @ 2400 fps = 1598 ft/lbs = 2166 Joules = 2.16 Kj

.50 AE = 300 grains @ 1550 fps = 1600 ft/lbs = 2200 Joules = 2.20 Kj

 

Thats WAY less than 300 KJ, even with a 20x110mm anti aircraft machinecannon round you only get about 57 KJ, 300 would probably be the energy of a main battle tank round. 

 

If its about the energy the powder charge itself contains, well, I have no freaking idea. The problem is powder varies a lot, you'd have to specify what powder is being used in that round. Its impossible to say.

 

In a nutshell: Wals, stop making ridiculous bets while being high on absinthe.

 

 

Yes, same joules. 

 

1 nutritional Calorie = 4186.8 joules = 4.1868 kj  

 

Amp Energy Overdrive energy drink has 220 Calories = 921.1 kj   so 300kj is probably reasonable for a smaller energy drink. 

 

For the bullet, the total energy is slightly higher than Woldan calculated.  There is some energy loss due to recoil, but the relative mass difference of the bullet versus the gun should make that fairly small.  Maybe 1% +/- of the muzzle velocity energy but that's just ballpark.  There is also probably some energy loss due to imperfect combustion and a bunch of other things I am forgetting. 

 

I don't think you're going to find enough energy loss to make up a gap that big though.

 

You can calculate recoil velocity here:    http://www.jbmballistics.com/cgi-bin/jbmrecoil-5.1.cgi

Edited October 18, 2013 by kgambit

[Woldan]

There is no energy loss, that data is from a fixed test barrel.

 

So its true, my breakfast has more energy than a couple of tank shells. Thats kind of disturbing.

[Azdeus]

Well, your porridge or breakfast cereals are'nt very likely to blow up on you though.

[Woldan]

Well, your porridge or breakfast cereals are'nt very likely to blow up on you though.

True, they usually only cause a series of small comparatively harmless explosions approx. an hour after ingestion.

[Walsingham]

So essentially, the key is the rapidity of the reaction, and the ease of initiation?

 

That is interesting...

 

So if you could somehow improve the ... I'm going to stop before I work out a way to make explosives out of anything.

[kgambit]

There is no energy loss, that data is from a fixed test barrel.

 

So its true, my breakfast has more energy than a couple of tank shells. Thats kind of disturbing.

 

Energy loss factors:

 

 

Heat transmission thru the barrel

Heat lost thru expanding gases

Incomplete combustion of the powder

Barrel friction

Recoil (sorry but conservation of momentum mandates this one - you might not notice the recoil with a weapon fixed to a test bench but it's there)

 

The last three account for less than 5% of the initial energy, but the first two are each comparable to the muzzle velocity energy.

 

You could probably lose up to 70% of the total energy thru all of those.  That fits with your total combustion energy of 7.5 kj and a muzzle velocity energy of 2.2 kj.  That's actually a bit under 30% so you're in the ballpark.  

 

@Wals .... suddenly I am seeing Snap Crackle Pop Rice Krispies in an entirely new light .... 

Edited October 19, 2013 by kgambit

[Walsingham]

I'm particularly glad that this has surprised some of you chaps as well.