Category Archives: Tech

Improved Ballistic Calculator

Graphic by David Bookstaber illustrating the trigonometry behind sight lines and ballistic trajectories.
Graphic I made to illustrate some of the concepts incorporated into the latest ballistic calculator.

While working on my ballistics book I got sidetracked building a ballistic calculator. I wanted to programmatically generate some examples, so 6 months ago I went to see what was available in open source. As I have noted previously, Python is preferred for this sort of hacking. I found this recently active Python project that looked promising and began to play with it. I encountered some bugs, noted them on GitHub, and was soon collaborating with the Ukrainian developer behind the project. Since then I have sporadically worked on adding features and improving the code in my fork here. These became quite extensive, and today we merged all of my work into his repository as a version 2 release!

One valuable feature set I added was to clearly handle non-zero look angles – i.e., when the shooter is sighting above or below the horizon. All useful ballistic calculators accept look angle as an optional parameter, but none that I have seen make it clear in their output if/when their distance and drop values are relative to the sight line or to the horizon.

One of the plots generated by the calculator, highlighting danger space for a specific target and trajectory.

Technical details: The calculator simulates a ballistic trajectory using standard aerodynamic drag models together with a point-mass model of motion, sometimes referred to as 3 degree-of-freedom (3 DoF). It incorporates atmospheric variables, including multiple wind readings, as well as models of the change in air density by altitude over a trajectory. It adds Litz’s spin-drift approximation to windage, so I like to call it 3DoF+ since spin is another degree of freedom. (I don’t claim 4 degrees of freedom because the spin isn’t fully modelled. Amusingly, Hornady published a calculator under the trademark 4DOF® even though theirs likewise provides only auxiliary approximations of spin effects.)

LED lightbulbs can jam garage door opener RF signals

This was a strange one to debug: I upgraded the LED bulbs in my garage door openers from 60W to 100W (equivalents). My wife’s garage door uses a track-mounted motor head with a lightbulb on each side. She began reporting that she couldn’t close the garage door after she pulled out. After some investigation using multiple transmitters we confirmed that it would reliably open from up to 100 feet away, but it would only close using the remote transmitters if they were within about 15 feet of the receiver, which is in the motor head … next to the lightbulbs … which are turned on by default when someone is in the garage or crosses the threshold, but usually off when approaching the garage from the outside with the door closed.

Sure enough: some (but not all) LEDs emit RF energy at the same frequency as garage door openers!

So the newer LED bulbs I installed were unintentionally serving as garage door opener jammers!

Chronos High Speed Video Camera for Shooting Analysis

Frequent readers know that I have been looking for high-speed video to go mainstream for years – ever since Casio dipped its foot into the consumer market with its F1 camera in 2008.

The sort of bullet-freezing high-speed video that has become familiar to YouTube audiences still requires a Phantom or Photron camera that runs well into five figures. However, there is finally a “pro-sumer” level high-speed video camera that fills the niche between 3-figure “action cameras” and those 5-figure professional cameras: The self-contained Chronos 1.4 is launching at $3,000 and offers 1.4Gpx/s throughput on a rolling 4-second buffer, which ranges from 1280×1024 @ 1,057fps to 640×96 @ 21,649fps! Aimed Research recently gave me an opportunity to test the beta version of this camera. I’ll show some of the cool things this camera can do over the next few posts.

Note that this was a beta device, and I didn’t have enough time to learn to optimize the camera at its limits. For example, here’s a 60gr .22 bullet leaving a barrel recorded at 9,000fps. With some more tweaking I expect I could have gotten the shutter speed low enough to show the bullet as a solid in each frame instead of a blur:

Subsonic 22 leaving barrel recorded at 8923fps

With time resolution in the thousands of frames per second we can see a lot of hidden phenomena. The following video of the same 10/22 rifle shooting the same 60gr .22LR bullet was recorded at 2,356fps. One surprising thing we can clearly see here is that the bolt bounces off of the breech when returning to battery.

Another thing we can see is something we heard during recent sound level testing: The unusual 60gr .22LR load is 50% heavier than the bullets for which this action was designed, and the case is 0.2″ shorter. As a result, the case clears the chamber less than 1ms after the bullet leaves the barrel, which causes a significant amount of pressure (and sound) to vent out the breech of the barrel. (A standard 40gr round doesn’t open the breech until 3ms after the bullet leaves the barrel.) If we wanted to tune this gun for this unusual cartridge, video like this would really help us confirm how changing bolt mass and spring rates affects the action.

2017 Product watch

Either I’ve stopped thinking ahead or markets are finally catching up: I’ve found existing or possibly imminent sources for most of the innovative products on my wish list:

High speed video is creeping into the mainstream: The just-under-$1000 Sony RX100MV can record a few seconds of HD (sort of) resolution at up to 1000fps.

Usable thermal imaging is widely available under $1000, and digital “night vision” is getting close to supplanting perpetually too-pricey image intensifiers. I found enough businesses working in this space that I’ve decided to wait to see what comes to market, rather than pushing for the particular integrated consumer product I have in mind.

In the consumer gun industry:

I haven’t written about them, but Flat Line bullets have brought revolutionary monolithic projectiles for long-range shooting to the masses.

Two years ago I asked for a three-mode trigger. I still haven’t seen what I specified, but the Echo trigger is a clever variant I hope to try soon.

Mantis has promised a second generation of their IMU that mounts to gun rails and interfaces with smartphones, allowing us for the first time to conveniently quantify and analyze recoil effects on firearms.

Bullpups continue to storm the mainstream. If you don’t like any of the increasing number of native bullpup autoloaders (AUG, Tavor, RDB, RFB, PS90 etc.) you can find conversion stocks for many popular platforms like the M1A, Ruger 10/22, Saiga, et. al. The KSG pump-action shotgun can actually be found at retail. From Europe we have clever single- and double-shot bullpups that should eventually be available at reasonable prices in America.

I don’t know that it’s in development, but at least someone thought it was worth patenting a new sealed-gap revolver.

Inexplicably, however, I’m still waiting for more heavy subsonic .22LR ammunition!

Curious Prices in the PC RAM Markets

A year ago I bought 8GB of DDR3 RAM for $45. I just bought another pair of DIMMs with identical specs and paid $77. Prices spiked to this level during 2013 Q1 and have not retreated, in what seems a blatant market violation of Moore’s Law. Some commentary on this situation notes that historically DRAM producers have whipsawed between cutthroat competition and nearly (if not explicitly) collusive pricing power.

Products I’m looking for in 2014


  • Supply in the firearms industry is finally starting to converge on demand. But reloaders are still grasping for powder, and .22LR is still absurdly scarce. We’re looking for both of those shortages to end by the middle of this year.
  • Expanding subsonic rifle bullets: Looks like this is finally the year for these to hit the mainstream market. Outlaw State Bullets and Lehigh Bullets have had some expensive offerings. But this year Norma is supposed to begin importing their Plastic Points, and Remington should finally have an offering tailored for their 300BLK.
  • .38 Supercomp Sig and Glock conversions. The caliber offers the ballistics of .357 Sig in the diameter of 9mm, which translates to more magazine capacity. Also, as a straight-walled cartridge it’s easier to reload.
  • Laser Doppler Anemometers: Solid-state devices for shooters, similar to laser rangefinders, that can measure downrange winds. Winds are the last primary ballistic factor that can’t be measured outside instrumented ranges. Even the most skilled long-range marksmen in the field have limited indicators from which to read and compensate for windage. Admittedly this technology is still some years off from commercialization.
  • Chemical laser guns. Well maybe not this year, but the technology is there for it.



  • High-speed consumer video cameras: GoPro may be inching back into this niche left by Casio four years ago. Their top offerings can now sustain 240fps at 480p, but I’m still looking for thousands of frames per second in a sub-$1000 camera, which is no stretch given the state of the art.
  • Reasonably-priced HD IP security cameras: For some reason these persist at over $200 when the state of the art should have them closer to $100.
  • Digital thermal and night-vision gear: No manufacturer seems to want to lunge for the tipping point. Equipment that is currently produced at a small scale, and therefore costs 4- or 5-figures, could be profitably mass-produced and sold for 3-figures to the sport and non-military security markets.

Carbonite Update

I’ve been using Carbonite Home Backup for active offsite backup since I recommended it over five years ago. My current backup consists of almost 300,000 files and 300GB of data.

I schedule full system backups to my NAS, but I count on Carbonite for both extreme disaster recovery and for intraday backup and changes. Although I’ve only used it a few times, the fact that Carbonite takes snapshots of files and maintains them for up to 30 days is helpful to recover accidental changes or deletions.

Recently I’ve discovered some shortcomings. Carbonite’s exceptional Tier 2 technicians (based at a call center in Maine) told me they have forwarded my suggested fixes for these to engineering as feature requests, but no changes have been promised.

The first batch of problems occurred when my primary disk failed last month. I restored from a local backup, and then wanted to use Carbonite to recover the most recent files and changes that were missing from that local backup. After some turmoil we determined:

  1. Carbonite doesn’t deal gracefully with being restored as part of a system image. It has to be reinstalled in order to recognize that its local cache doesn’t reflect the offsite backup.
  2. Carbonite doesn’t efficiently perform automatic recovery. Instead of first checking to see what files are already restored and up to date it queues the entire backup for recovery and then iterates through every file, taking 1-2 seconds per file just just to recognize it’s already there and up to date. Consequently, even though I was only missing a few hundred files it took 3 days for Carbonite to finish its automated recovery.
  3. Carbonite doesn’t distinguish between deleted and current files. So my automated restoration included every backed-up file I had deleted in the last 30 days, which I then had to hunt down and re-delete!
  4. Carbonite doesn’t provide enough tools for a user to work around these problems. If, for example, you could search or sort your backup based on file times and other standard metadata you could manually restore what you want. Presently you can only run restoration based on file locations.

Another shortcoming was revealed after I migrated my system to a SSD, which caused all my user data to change from local drive “C” to “D.” There is no way to tell Carbonite that my 300GB backup has simply changed drive letter. As far as it’s concerned, I deleted 300GB from C and have 300GB in new data to backup from D. Which is irritating, because for the less expensive plans Carbonite throttles the data upload speed based on how much is in your backup:

  • Up to 35GB it backs up at 2Mbps
  • Up to 200GB it backs up at 512kbps
  • Beyond 200GB is backs up at 100kbps

So if I don’t want to immediately purge my backup and start from scratch it will actually take 9 months to bring my backup up to date. If I do purge my existing backup it will still take 4 months to return to my backup to its current state!

New Computer: and Upgrade to SSD

In past months I bought two laptops for work. One had a SSD and I was blown away by its performance. The other had Windows 8 and I was blown away by how bad it was. Maybe Windows 8 shines on tablets and smartphones, but for now I’m sticking to Windows 7. Meanwhile, I’m eager to get SSDs onto my machines.

Amazon just had an amazing sale on Intel’s top-of-the-line 520 Series SSD: $130 for a 180GB SATA-6 drive rated at 550/520MBps sequential read/write and 50k/80k random read/write IOPS.

My existing primary desktop didn’t have SATA-6 support — essential to fully exploit that SSD performance — and my secondary desktop was becoming so unreliable I dedicated this weekend to upgrades. Since my primary desktop was over 3 years old this meant a new motherboard and CPU. I’ve been assembling AMD-based desktops for at least the last six years. But researching current offerings it looks like Intel has really reclaimed its technical superiority over AMD. (Aside from its graphics innovations for gaming, the last triumph I remember for AMD was when it launched its 64-bit Opteron server processors in 2005. I bought a pair for a research server as soon as they hit the market at $860 apiece.) I don’t play games and I don’t overclock, which tends to leave me looking for efficient hardware that contributes to a quiet, cool computer. Intel’s i3-3225 won this bid with its preponderance of associated innovations, including cutting-edge 22nm construction, two multi-threading processing cores, and Intel’s top-of-the-line HD-4000 integrated graphics — all provided with a peak consumption of only 65W. The CPU was $130, Gigabyte GA-H77M-D3H motherboard was $95, and 8GB of dual-channel DDR3-1600 CAS-9 RAM was $45.

The trickiest part of this hardware-only upgrade was splitting the “operating” portion of my primary 1 TB HDD out to clone to the SSD. In order to do this I first cloned the drive to another 1 TB HDD, and then deleted bulk data until I was left with a small enough set of operating system and program files to fit on the SSD with at least 20% room to spare. Complicating this process is the fact that Windows is tightly coupled to the “User” folders, so even though most of those were bulk data that doesn’t belong on the SSD I couldn’t just outright delete them (as I learned the hard way). Instead I had to pare them down and then, once running from the SSD as Drive “C” redirect the locations of reserved Windows User Folders to their copies on my original drive, which is now running as “D.”

End result? Awesome: The operating drive’s speed has always been the biggest bottleneck in booting and loading programs. With a SSD (and Windows 7’s native support for that hardware) those now occur with minimal delay, and without the drama of a spinning disk’s read head fluttering back and forth over the platters to pick up scattered data blocks.

Hey Verizon, What century is it?

Among the many telecom services I use is Verizon FIOS. I was checking rates today and discovered that unless a Verizon landline customer purchases an international calling plan they will pay $3.41/minute on any international calls!

Is gouging the unsuspecting, uninformed, or desperate consumer really a good business practice for a large, regulated, or brand-name franchise?