Welcome to the Boards, Sleepy Weasel.
That’s exactly what I was trying to say. Sometimes I have to be too brief when I’m trying to post something from work.
Me too. Ever have to use code?
Boss is coming… the duck is in the henhouse… I repeat, the duck is in the henhouse!
KVAK!
No, I have nothing to add.
Thank you for your time.
Not quite. There is a difference between an explosion and a burn, or a detonation and a deflagration.
(note: most of the following was in another post I made last week that not one person read…so I’m anxious to use it again)
For example, if we want to compare detonation (explosion) and deflagration (burning), we can look at this simplified example which takes a close-up view of the flame front region:
Try to visualize a one-dimensional stationary combustion wave of a flammable gas and air mixture in a tube. We will assume this is a premixed flame, which is defined as one where the reactants are mixed perfectly before the chemical reaction. (as opposed to a diffusion flame, where the reactants diffuse into each other during the chemical reaction). Wood burning generates a diffusion flame, as opposed to a torch or gas burner which generates a premixed flame.
___________________________________________________________
|
(Unburned gas) |F (Burned Gas Products)
|l
U1-------> |a U2--------->
|m
|e
p1, T1, P1 | p2, T2, P2
_____________________________|______________________________
Where U is the velocity of the gas, p is the density, T is the temperature, and P is the pressure, and C is the local sonic velocity. By looking at these variables, we can express relations between the two sides of the flame front to say whether what we have is either:
-
deflagration - where the combustion wave propagates at subsonic speed (controlled burning, in other words). These are found in Region III of the Hugonoit curve (and yes, technically, Region IV, except it is very hard to get anything into region IV since it is very hard to get combustion products to depart from the combustion wave at supersonic speeds), or
-
detonation - where the combustion wave propagates at supersonic speed (an uncontrolled burning). These are found in Regions I and Regions II of the Hugonoit curve, with said regions being seperated by the Upper Chapman-Jouget point, which divide them into Strong and Weak detonation points.
Deflagration and detonation are divided by Region V of the Hugonoit curve, which is an imaginary region since the Rayleigh-line expression implies that U1 (see below) is imaginary, and thus it is a physically impossible region.
But I digress.
For these cases, we have the following relationships:
Property Detonation Deflagration
------------------------------------------------------
U1/C 5-10 (supersonic) 0.0001 - 0.03 (subsonic)
U2/U1 0.4-0.7 (deceleration) 4-6 (acceleration)
P2/P2 13-55 (compression) 0.98 (explansion)
T2/T1 8-21 (heating) 4-16 (heating)
p2/p1 1.7-2.6 0.06-0.25
Which just tells us in a stable flame, we have a subsonic flame front, acceleration of hot exhaust gases away from the flame, a slight expansion of the exhaust gases due to lower pressure, a large heat addition (duh!), and a decrease in density. As opposed to detonation, where the supersonic flame front causes a large spike in pressure and density, casuing the “knock” one hears in car engines, for example.
Err…the property in the table listed as “P2/P2” should read “P2/P1”, should anyone care.
Una
Can someone give me an Anthracite to English translation please?
I got the difference between uncontrolled and controlled burning, but what does that have to do with the speed of sound?? I’m really missing something here.
Thanks for that physics lesson, Anthracite (whew, now that’s a hard core answer).
My experience is from the EOD side, where munitions, etc., are involved, thus everything is a burn.
Ok, Anthracite, here’s the over-simplified kiddie version of what I got from your explanation of the difference between a detonation (explosion) and a deflagration (burn).
When stuff combusts there is a wave of hot gas and combustion materials (the combustion wave) that passes along and from the burning stuff.
When that wave moves along at less than the speed of sound (for the location where the combustion is happening, because the speed of sound varies with local conditions), we have a deflagration (burn). When that combusion wave spreads at more than the speed of sound, we have a detonation (explosion).
So, did I get the basic concept?
Not to nitpick, well, ok, I’m nitpicking, but doesn’t a wave require at least 2 dimensions?
Really not nitpicking this time, I promise. I was curious how you’re defining the terms “controlled burn” and “uncontrolled burn” in these examples.
Okay,
So what’s the deal with the energy of the round? I know these things have kinetic energy, and my 5.56 55gr FMJ has a hell of a lot more KE than my .40SW 165gr . . . Just how do they measure this? And what’s the equation based on speed and weight? I’ve tried to find it, but there’s something more detailed than my college book’ll tell me. . .
I’m an Electrical Engineer. I slept through freshman physics.
Tripler
I love my AR. Bought it on the 3rd of July, shot it on the 4th.
The “deal” depends on what’s important to you. If you want to punch holes in paper, both will do it, but the .223 will do it a lot further away.
If you want to punch holes in large unwanted household visitors, there are a number of other factors. For example, are you shooting the .40 from a handgun or from a carbine like Ruger’s PC? If you’ve got the maneuvering room to use a carbine, the extra energy of the .223 would make me feel a lot more secure.
On the other hand, I carry a .40 with a 6 inch barrel as a backup for hog hunting, and know that at close range it will stop a hog faster than a .223 will, mostly because the fat heavy .40 with the right ammo will punch through parts of a hog that would stop a .223 round.
In the “live target” scenarios, the muzzle energy isn’t always necessarily as important as the amount of that energy you can actually transfer to the target. It doesn’t take much to put holes in paper, but live targets are another thing. In cases of over-penetration, the energy retained by a bullet leaving the target is wasted. I know of agencies that use .223’s loaded with ballistic tips because they offer the flight & functional characteristics of the FMJ, while developing dramatic expansion and energy transfer on soft targets, and reduce the chance of over-penetration injuring hostages and bystanders. Because they can transfer the total energy of the projectile, they can take advantage of the increased capability of the round, rather than resort to pistol caliber submachine guns and carbines.
No, maybe I didn’t really explain enough . …
I realize the difference in energy, and I realize that for CQB, I’d carry a 9mm or .40SW. While I like the .45 for knocking Communists down, it’s just got no range.
What I meant was, as a full fledged geek, how do I put the kinetic energy into numbers? Is it measured in foot-lbs, oz-ft sq? Get my drift? I know which caliber is big, and what’s good for like you said “punching holes in paper”. Just curious how the industry measures it. . .
Tripler
Much obliged. I am a true geek.
Maybe you gun nuts can help me:
I’ve been having a problem with defining a weapon. Back in the IDF, we had two major infantry weapons, which we called the “M-16 Long” and “M-16 Short”. Now, the “long” was your standard M-16A1, I believe; however, I’ve been having a problem finding out the real name of the “short”. It had a black, metal “folding” (actually telescoping) stock, and short, rounded foregrips; the barrel length after the front sights was as long as that of the “long”, and it was capable of select fire (although we were tought to use automatic fireonly in extreme circumstances). Was it the AR-15? M-4?
Sounds like an M-4 Carbine. Special forces use it, and lately at my base, the Dept of Energy carries them (along with a lot of other cool toys). I’ve seen 'em in gun shows, but couldn’t cough up the $3,000 to pick it up.
Sorry, my bad… In answer to your amended question:
- Care
- See #1
Alessan, the firearm you’re referring to is the CAR-15. This was an M-16 with a short (14.5") barrel and a telescoping stock. Some CAR-15s had the standard, fixed M-16 stock. Other variants were the XM-177E1 and XM-177E2. These had shorter barrels, 10.5" and 11.5", respectively, and can be identified by a long flash supressor. I’ve read that the flash supressor also modified or attenuated the sound in some way, but it’s hollow (no baffles inside) so I don’t know how much effect it had.
The differences between the M-16 and the M-16A1 were: M-16 had a swiveling rear swivel; the A-1’s was fixed. The M-16A1 had a forward-assist plunger. Early M-16s had shiny, not parkerized bolt carriers. The A-1 had a closed flash supressor and the M-16 had a three-prong open flash supressor. I’m sure there are other mods, but I’ll leave that to someone who knows more than I do (or has a reference book handy).
The latest version is, I believe, the M-4. I’m sure someone will be along presently to correct me if I’m wrong.
I’d hardly say you were wrong, but from the A1 there have been advancements, including the imporved rear sights of the A2, the flat-top A3, etc. It’s hard to say what’s the “latest” since there are so many companies making their own versions. I went with the Bushmaster but avoided the M4 type barrel in favor of a HB model. Tripler, if someone wanted $3000 for something they passed off as an M4, you must be in California. My carbine ran around $700, for the flat-top with a removable carrying handle, but this is TX where we don’t ban much.
BTW, Alessan, how do you define “gun nut” anyway?
Trip, this is coming from the rec.guns FAQ, specifically, the terminology and acronyms section:
A “grain”, for those interested, is 1/7000th of 1 pound.
Thanks, guys. They’re definately the CAR-15 and M-16A1, respectively. The CAR-15 is a great weapon - light, short and accurate, especially with “red dot” optical sights.
BTW - what’s a “flat-top” M-16? Did they take away the “handle”?
Oh, and -
The same way as I define a “hiking nut”, a “golf nut” or a “science fiction nut” - someone who has a hobby he is passionate about. Why?