Odd, that’s a long ago industry standard name for any type of milspec or similar flash hider. Here’s copy from a Aero Precision AR15 assembled upper:
"This complete upper includes our ATLAS R-ONE Handguard! The R-ONE handguards are designed with size and weight in mind, while still providing plenty of real-estate to accommodate any attachment needs the end user may have. Our proprietary ATLAS attachment system is a durable and dependable mounting platform, maintaining a slim profile while still providing the strength and stability customers have grown to love from Aero Precision handguards.
M4E1 Threaded Assembled Upper Receiver 12" M-LOK ATLAS R-ONE Handguard 12.5" 5.56 Government Profile CMV Barrel, Carbine Length Low Profile Gas Block and Carbine Length Gas Tube AR15 A2 Birdcage Flash Hider"
From Google Earth I could estimate de distance between the roof vertical line as 0.6m, therefore the distance of 6 horizontal lines is 35’’ that is close to whole gun length.
I re-oriented the image and made no changes to compress it or enlarge any section of it, just to make it easier to measure, and put a virtual tape measure on it for context. The tape measure is obviously not to actual size but gives reference.
My real AR15 buttstock fully extended to the front of the receiver is 18.5" for context.
In this image, the ruler shows 4.25" from buttstock to front of receiver, and 3.75" barrel chamber to tip. That would translate into approximately 17" to 18" in my opinion. Looks more like 17" to me. I think we can narrow it down to 16.5" to 18" with the muzzle device.
However, these are crude measurements and being off by even an inch would throw the entire calculation out.
In my experience, pre-pistol brace era (from which this rifle was apparently purchased circa 2012), gun companies universally built their barrels to at least 16.25" or 16.5" to make ultra certain they were compliant with the law requiring rifle barrels be 16" long.
So the rifle in question might very well be 16.5" barrel with a 1/2 or 1 inch muzzle device.
jesus christ man, okay we’ll say it’s a 16.75inch barrel. sound good??
it’s unreal the lengths people have to go through to verify a basic thing you should be able to gather from just using your eyes, but even with picture evidence staring you in the face you still cannot admit it’s a 16" barrel. even if it’s 16 point whatever number, nobody would call it that except you, everyone else would just call it a 16 inch barrel. do you know why? because a 16 inch barrel AR-15 is the most common kind…
Thanks for doing that, @jmholford. I did some experimenting and found that with the changes that I made to the perceived recorder positions for shot 10, a different adjustment value was needed to put shot 10 on the south barn. The details are shown in the attached PDF file. Adding snick adjustments to shots 9 & 10.pdf (656.0 KB)
To be clear, this does not solve anything. The analysis of shots 9 & 10 continues to confound me.
I made a video this afternoon that others may find interesting. It slows down the shots to 1/10th speed. I wanted to listen closely to the shots to see whether I could distinguish between the shorter “snick” sound of a supersonic snap as opposed to the smoother sound of the rifle’s report. This video plays the sequence of 10 shots twice. The first set is normal audio, and the second set has some digital filtering done to suppress the background noise.
Question: Are you Greg Nichols, and do you find it bizarrely coincidental that one of the suspicious characters is Greg Nicols? I’ve never in my life heard of or met a Greg Nicols and now on the same “case” there’s 2 people with the same very unique name pronunciation?
Chris, thank you for your coverage of this issue and so many others.
Is it possible that the videographer was on the side of the building during the first three shots and for the remainder came around the corner and now had line of sight to the guns?
High frequencies are very directional, much more so than mid and especially low frequencies. Have you ruled out this issue as a contributing factor?
Thanks again.
@pk2019, no I did not realize that. The file I used is called “LEO montage - Cruiser + Why not on roof.mp4”. I downloaded it from a Mega link that someone posted on this forum. It only has one audio stream in it. Where do I get the original video that has all three streams?
You’re right, but bear in mind that (1) they also depend on the strength (amplitude) of the sound; and (2) modern cellphone mics are omnidirectional and pretty good; (3) there were differences as well in the very non-directional bass frequencies.
You’re not going to get much of a difference walking a few meters recording gun blasts, even around a corner. But whether it is enough of a difference is valid, so good point.
Wow, @vt1 . Thanks for doing those calculations. Just to be clear, you use the estimated speed of the bullet to determine the angle of the sonic cone. From what I’ve read, the internal angle of this cone decreases as the bullet’s speed increases past Mach 1.
Let me make sure I understand all the variables in Eq. 12
b = distance from shooter to the closest point of approach to the audio recorder
Vm = muzzle velocity
h = distance from the recorder to the bullet’s path of travel
Vc = speed of sound
