[atkamano]

I have been looking for subsonic 40 s/w ammo for a while now, and the heaviest bullet I could find is 180g and runs at about 980ft/s at muzzle.

Is there any other bullet in 40 s/w that is heavier and travels slower? Maybe 900 ft/s....?

 

[DanaT]

My question is WHY????

If you want subsonic go with 45ACP.

-Dana

 

[[TASF]Overkill]

Oh, maybe... because he has a .40?!

 

[atkamano]

thank you overkill.

I have an xd-40. I am in the process of obtaining a suppressor for it. I need subsonic bullets to maximize the suppression.

 

[agalindo]

Maybe I'm wrong but isn't the speed of sound about 1100 fps most 180gr factory loads are 970-990 fps that would make them subsonic. You could reload for lower speeds.

 

[DNM]

I'm new to firearms and all... so my stupid question will be... why would you want a round that's heavier and slower??? What's wrong with the 165g at 1150 fps???

 

[[TASF]Overkill]

For use with a suppressor.

 

[87-51]

Like was said, most 180 gr loads are subsonic. There are 200 gr bullets available if you reload.

 

[AresXD40]

Speer Gold Dot 40 S&W 180 Grain Jacketed Hollow Point Travels @ 985FPS with 400FT/LBs of Muzzle Energy.

PMC Gold 40 S&W 180 Grain Starfire Hollow Point Travels @ 985 FPS with 388FT/LBs of Muzzle Energy

Hornady TAP Personal Defense Ammunition 40 S&W 180 Grain Jacketed Hollow Point Travels @ 950FPS with 361FT/LBs of Muzzle Energy.

Hornady Custom Ammunition 40 S&W 180 Grain Jacketed Hollow Point XTP Travels @ 950FPS with 361FT/LBs of Muzzle Energy

I researched for a little bit and found those options for you. I went with all Hollow Points and top quality ones at that, which have been field proven. I personally use the Speer Gold Dot 180 Grains. I believe it travels suffiently slow enough for your purposes.

 

[[TASF]Overkill]

Speer Gold Dot 40 S&W 180 Grain Jacketed Hollow Point Travels @ 985FPS with 400FT/LBs of Muzzle Energy.

PMC Gold 40 S&W 180 Grain Starfire Hollow Point Travels @ 985 FPS with 388FT/LBs of Muzzle Energy

How is it possible for the muzzle velocity to be the same and the weight to be the same, but the muzzle energy different?

 

[AresXD40]

Different company, different powders, different burn rates, different powder loads. Simple as that. Every powder burns differently from different companies.

 

[agalindo]

Powder and burn rates have nothing to do with calculating muzzle energy.
From one site:
Energy = Bullet Weight times Velocity Squared divided by 450395
From another site:
Velocity (in F.P.S.) x Velocity x Bullet Weight (in grains) divided by 450,240
From yet another site:
E=MV2/450400

 

[AresXD40]

OK then agalindo you explain why there is different energy levels for all of those rounds I posted.

If the bullet weight is the same, assuming that the manufactures standard is up to par and isn't producing overweight or underweight rounds. IE 185 on some, and 175 on others.

Why else would there be different levels of muzzle energy?

Also powder DOES have something to do with it. Different amounts of powder produce different pressure levels. Hence the reason why +P rounds have higher pressure levels and more power. The faster the bullet travels it seems the more energy it produces according to your site references you posted.

Just like my M44 Mosin Nagant firing a 180 Grain 7.62x54R Winchester FMJ round produces a Muzzle Velocity of 2579 and a Muzzle Energy of 2658FT/LBs. Why? It has more powder, a longer barrel and the ability to make better use of the burn time of the powder and pressure created by the powder load.

 

[[TASF]Overkill]

OK then agalindo you explain why there is different energy levels for all of those rounds I posted.

I wouldn't have asked the question if it was a simple well known matter of physics.

Powder imparts speed X to the bullet. The bullet weighs Y.

X and Y, I believe, are the only factors in calculating energy. Something weighs so much, and is travelling so fast, for so much energy.

If the speeds are the same, and the weights are the same... how are the energies different?

Saying "It's the powder" doesn't make any sense.

The faster the bullet travels it seems the more energy it produces according to your site references you posted.

Exactly, but the bullets are supposedly the travelling the same speed.

 

[AresXD40]

Hmm... Didn't even notice that. Well powder is part of it, however I believe I'll step down from this one because I tripped over my own information if you know what I mean. Well now I really can't explain it, with the exception of different pistols, different testing gear, who knows. In this particular case I believe the best thing to do would be to aquire your own testing gear, borrow some and do your own tests from the XD. Stepping out now...

 

[Delija]

Overkill]
If the speeds are the same, and the weights are the same... how are the energies different?

Seems like the energies should be identical since the mass and velocity are the only variables.

Powder burn rates, muzzle length, anything else would be irrelevant after the projectile leaves the barrel.

I wondered about the shape of the bullet, but since that is not a part of the formula (formulas) that seems not be a factor. Although it does seem like a needle shaped bullet and a spherical bullet would impact with different degrees of energy. But since the formulas do not take shape into account at all, I suppose what seems and what is must be different.

Good question. It would be interesting to really know for sure. The formulas posted are slightly different. So maybe the shape has some marginal impact on the "impact" (huh?). Perhaps there is a little "wiggle room" for the formulas because of this, and that's why there is a very slight discrepancy in the numbers given.

Peace,
D.

 

[stealthsniper]

Simply stated, mass and velocity are the only contributors to energy. The basic formula is as follows:

• E = m/2 * V^2

Let's compute using the data from the two disparate rounds (180gr, 985f/s). The first step is to convert to standard metric units, otherwise we'll have a ton of base conversions to deal with throughout.

• 180 gr = 0.0116638 kg
  985 f/s = 300.28 m/s

With these figures, we can compute the energy in joules, which can then be converted to foot-pounds.

• E = 0.0116638/2 * 300.28^2
  E = 0.0058319 * 90168.0784
  E = 525.8512164209599 J
  
  J = 0.7375622 lb/ft
  E = 387.8479672 lb/ft

As you can see, Speer is somewhat unrealistic in their figures. It has nothing to do with powder burn rates, bullet shape, the alignment of the planets or even the price of tea in China. It's physics, pure and simple.

 

[manygunner]

Stealthsniper is right, the manufacturers fudged their data to entice buyers. It's the oldest trick in the book. Either that or some flunkie in the ad department said," hmm, so what if I typed the wrong thing, who will know?" The cold hard figures do not lie.

 

[agalindo]

What I was trying to say was that the formulas were slightly different from each other and that would account for the diffence in muzzle energy. The two companies used a differnt formula.

 

[gonzo]

Speed of sound in air at 0 degrees C (32F) = 1085 ft/sec
Speed of sound in air at 100 degrees C (212F) = 1268 ft/sec

c = square root (gamma*R*T)

c = speed of sound in a gas
gamma = gas constant at standard temp and pressure (insert 1.4)
R = 286 (ideal gas constant)
T = absolute temperature in K (degrees C plus 273.15)

(the answer is in meters, and you have to convert to feet)

In short, a round traveling under 1050 ft/sec should be subsonic unless you intend to shoot Santa at the north pole in January. At -50C (-58F) your speed of sound drops to 980 f/sec, and Santa will hear the crack of the bullet (if you miss).

At room temperature, the speed of sound is closer to 1125-1140 ft/sec. General assumptions are made regarding air pressure, so attempts on Santa at sea level may be different than attempts at the top of a mountain. And Santa's elves pack .50BMG, so be careful out there!

(edit to correct and change "square" to "square root")