Title: Forensic acoustic proof of SECOND shooter in the Las Vegas massacre Source:
[None] URL Source:https://www.youtube.com/watch?v=JxmEFeKy8aI Published:Oct 11, 2017 Author:Mike Adams TheHealthRanger Post Date:2017-10-11 00:40:47 by A K A Stone Keywords:None Views:39264 Comments:148
#73. To: A K A Stone, VXH, buckeroo, tooconservative, cz82, redleghunter, sneakypete, Pinguinite, Vicomte13, Liberator, Deckard (#1)
Found this interesting video.
Adams assumes a shooter using an AR-15 with .223 Remington 55 grain ammo.
He states 20% humidity.
He states a 925 m/s bullet velocity which is ~3034.8 fps.
He specifies a 16.5" barrel, but a 3034.8 fps initial velocity would seem to indicate a 20" barrel or different ammo.
I believe the white board has an error. The flight time should be 0.532s, not 0.528s.
It lists both the 400 yard flight time and the lag time as 0.528s. This would mean the bullet velocity was precisely double the speed of sound, and that double 0.528s, or 1.056s would be the 400 yard travel time for the speed of sound. The time of sound travel for 400 yards at 1130 fps is 1.062.
He cites his use of a gundata ballistics chart for travel time.
gundata indicates for 400 yards, the time of travel is 5.32s, specifying a standard 55gr Remington .223 bullet leaving the barrel at 3,215fps. Adams also specified a 16.5 inch barrel, but it seems an AR-15 with a 16.5 barrel does not achieve 3,215 initial velocity.
Testing with different barrel lengths indicates an AR-15, 16.5" barrel, with Remington .223 ammo, does not achieve 3,034.8 muzzle ("initial") velocity.
With a 20" barrel, the same setup gets 3,071 fps muzzle velocity.
A 25" barrel gets it up to 3,221 fps muzzle velocity.
A 16.5" with Federal M193/55 gets 3,187 fps muzzle velocity.
A ballistics chart indicates that a Remington .223 will not get the stated bullet velocity.
Assuming the shots were fired from room 32135, and that end of the Mandalay Bay Hotel was 1208 feet from the base of the bandstand, and that a bullet struck the pavement at or near the base of the bandstand, the long side a right triangle would be 1208 feet and the short side would be the height of room 32135.
The building claims a height of 480 feet and 44 stories, for an average of 10.91 feet per story. The 32nd floor would be 338.21 feet up. (31 x 10.91, base of floor 1 has zero height).
With sides of 1208 and 338.21, the hypotenuse would be 1254.45 feet.
The actual distance the bullet traveled would be more than that as it would not follow a straight path, but would follow an arc.
Using estimates of distance to striking the venue surface of ~1250 feet, and detected lag times of 0.559 sec and 0.374 sec, the slower bullet made the 0.374 lag time; the faster bullet arrived .559 sec before the muzzle blast.
At 1130 fps, the sound would cover 1250 feet in about 1.106 seconds.
A bullet making the 1250 ft trip .559 sec before the sound, made the trip in .547 sec.
A bullet making the 1250 ft trip .374 sec before the sound, made the trip in .732 sec.
1250 feet in .547 sec is an avg velocity of ~2236 fps.
1250 feet in .732 sec is an avg velocity of ~1708 fps.
This assumes both shots were taken from the same location.
What bullets were used can be ascertained by collecting the bullets. What was left in the room should be inventoried, along with what guns were in the room.
Most mfgs recommend a minimum velocity of 1800 fps for proper expansion. The so called "magic number" associate with elk hunting is 1200 lb ft Energy. Below that is risky and I prefer 1400 lb ft as my personal standard. Although every gun is different the ammo mfg. Will put their tested numbers out for their loads. According to Federal their TBT 165 gr out of a 308 maintains 1939 fps and 1377 lb ft at 500 yards. Mathematically that should do the job as long as the bullet hits it's mark. Federal lists the same weight game King at 1708 FPS and 1069 ft lb at 500 yards. Obviously not the best option. If you keep 400 yards and in either a 150 or 165 gr factory loaded bonded round should work fine on elk. You just need to find the one that goes exactly where you want it to every time you press the trigger.
This would suggest the possibility of the 1708 fps round being a .308 (or whatever else gets around 1708 fps at 400 - 450 yards.
This is a .223 ballistics chart (external) generated using our ballistic trajectory calculator. Based off a standard 55gr bullet leaving the barrel at 3,215fps and follows the bullet trajectory all the way to 1000 yards in steps of 50 yard increments. The charting shows the range, drop (based off a 1.5" scope mount), current velocity, energy, and time in seconds in relation to the bullets movement through space and time. This chart does not account for atmospheric conditions, so if you want to take in to effect these things check out the calculators official page. The Ballistic Coefficient for the .223 Remington, Remington Metal Case, 55gr is 0.202 (in this example) but, but may also range from .185 bc to .257
