Author Archives: David Bookstaber

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!

Everyday Carry Knives: Kershaw SpeedSafe

I’ve had a Kershaw Cryo G10 for two years, and during that time I’ve pretty much stopped carrying any other knife. It clips and rides more comfortably in the corner of my pocket than any other. I love the SpeedSafe assisted opening feature. I haven’t abused it, but I can at least tell that the steel will take and hold a decent edge. And since it can be replaced for under $30 I don’t feel the need to baby it.

I took advantage of a sale this week to add three more SpeedSafes to my collection. Top to bottom is a Filter, Brawler, Cryo 155Ti, and my two-year-old Cryo:

Subsonic .22 caliber

Following some renewed interest in my old post on The Missing Subsonic .22LR Market, I figured it would be worth posting some of the notes I made during my last journey through that topic. The purpose of that post was to wonder why Aguila is the only manufacturer in the world making .22LR bullets significantly heavier than 40gr. To explain why that’s of any interest let’s take a few steps back.

Why the obsession with subsonic bullets? The answer is, “Peace and quiet.” A typical center-fire rifle shot meters about 165 dB a few feet from the muzzle. A good silencer reduces that by 30-35 dB, making it hearing-safe to shoot, but by no means “silent,” nor even quiet. The largest component of the sound signature of a silenced rifle shot is the bullet’s “sonic crack”: A supersonic projectile creates pressure waves that reverberate along its entire flight path, and in the case of a rifle bullet these create roughly as much sound as an unsuppressed .22 rimfire shot. In fact, people working in the target pits hundreds of yards downrange from a firing line are generally required to wear hearing protection because the sonic crack of bullets passing close overhead can still cause hearing damage.

So at some point after one buys a rifle silencer one begins to wonder how to make it even quieter. Having absorbed most of the muzzle blast in the silencer itself the next step would be to eliminate the sonic crack. This requires changing the rifle load so that the bullet’s velocity is reduced from its usual 2500-3200fps to a subsonic velocity — 1100fps under standard atmospheric conditions.

“No problem. Let’s just double or triple the bullet weight,” one might naively say. Unfortunately it’s not that easy. A 55gr .223 lead bullet, which shoots about 3000fps, is typically 3/4″ long. A 150gr bullet driven by the same load would be subsonic, but to be reasonably aerodynamic it would also be almost 2″ long, and this is where we run into some inconvenient facts about ballistics. We’re talking about rifles, and why are they rifled? In short: to keep the bullet pointed in the right direction. Rifling imparts spin to bullets fired through a barrel, and it turns out that the twist rate of the rifling is somewhat particular to the bullets a gun is designed to shoot. A bullet has to spin at a certain minimal rate to maintain stability throughout its flight. If it doesn’t spin fast enough then aerodynamic forces will cause it to yaw or even tumble, which disrupts all of the careful work that went into making a rifle that could send a bullet over a long and accurate flight path.

Spin Stability

One of the most accessible spin models for small caliber bullets is the “Miller Stability Formula” which estimates gyroscopic stability based on four parameters:

  1. Rifle twist rate
  2. Muzzle velocity
  3. Bullet length
  4. Bullet weight

Holding all else constant, bullet flight stability increases with higher muzzle velocity or twist rate (either of which cause it to spin faster), and decreases with shorter or lighter bullets (both of which require the bullets to spin faster to sustain stability).

According to the Miller formula a 2″ .223 bullet weighing 150gr and shooting 1000fps would require 1:4″ rifling (that’s one full turn in just 4″ of barrel length!) to stabilize. Neither bullets nor barrels are made anywhere near those specifications. The fastest rifling you can find in .22″ barrels is a sharp 1:6.5″, which at subsonic speeds is barely sufficient to stabilize the heaviest .22″ rifle bullets on the market, which are 1.16″ long 90gr boat-tail target bullets.

Granted, at subsonic velocities aerodynamic profile isn’t as important. So what are the heaviest bullets we can shoot with a .22 rifle? Lead has a specific gravity of 11, which means that for a given volume it weighs 11 times as much as water. Water weighs 253gr per cubic inch, so a .22″ diameter slug of lead (which has a volume of .038 cubic inches per inch of length) weighs 106gr per inch. If we are willing to fire a ballistically inefficient flat-nosed, flat-base, unjacketed lead slug then, according to the Miller Formula, a standard 1:9″ barrel can just barely stabilize about a 90gr (.9″ long) bullet at 1000fps.

Extreme Shock makes pricey 100gr tungsten-powder slugs that are slightly denser than lead and will stabilize in 1:7″ barrels at subsonic velocities. If you don’t mind spending over $1/round that could be a decent route to go. But if you try lighter or pointier bullets you run into other problems related to case volume: Hodgdon has published two subsonic loads for .223 Remington. One of them uses a tiny amount of fast-burning powder, which turns out to be very problematic. After two out of six test loads I made fizzled and left the bullet stuck in the barrel Hodgdon techs noted that their TiteGroup subsonic recipes are very sensitive to variation. They now recommend only using the exceptionally bulky TrailBoss powder, which will reliably get the bullet out of the barrel, but (at least in my experience) not at very consistent velocities.

My conclusion: Why bother? Due to the stability constraints in .22 caliber with conventional bullets you can’t go much past 70gr anyway. Forget trying to get a .223 autoloader to cycle on such light loads. Meanwhile, for a fraction of the price you could be shooting Aguila’s 60gr .22LR, or any number of grades of 40gr .22LR.

.22 diameter bullets

10/22 Precision Rematch

KIDD 10/22 in Archangel stock, Ruger 10/22 with Feddersen barrel in Vantage stock

These are both Ruger 10/22 style semi-automatic rifles built for shooting .22LR with maximum accuracy. On top is an $860 rifle built entirely by KIDD Innovative Design. The receiver and trigger are milled from aluminum, and the bolt from hardened steel. The single-stage trigger is also a crisply machined assembly that adjusts down to a pull of just 1.5 pounds. The lightweight barrel is guaranteed to group inside of half an inch at 50 yards. The gun here is screwed into a comfortable $100 ProMag Archangel Target stock

Do you have to spend $1000 to get an accurate .22 rifle? Expert barrel maker Fred Feddersen says one of his $170 barrels will turn an off-the-rack Ruger into a gun that can compete with any custom autoloader. So the second gun shown is a standard Ruger 10/22 receiver and bolt onto which I swapped Feddersen’s barrel. Of course I don’t think I can really shoot that well with a standard trigger, so to be fair I bought another $200 KIDD trigger assembly for it. The gun is shown here screwed into a beautiful $175 Tactical Solutions Vantage laminated stock.

I tested these for precision last year. This time, with a few more ammo types, I also tested all ammo both with and without a suppressor.


Both guns were cleaned and then shot through the following sequence of 40gr subsonic target loads:

  1. 30 rounds SK Plus
  2. 25 rounds SK Match
  3. 15 rounds Eley Match
  4. 40 rounds CCI SV
  5. 40 rounds Aguila SuperExtra

All rounds were fed from the same transparent Ruger 10-round box magazine. This time the KIDD ran with no hiccups whatsoever. The Feddersen-barreled Ruger, shot second, had one failure to feed with the CCI and one with the Aguila.

The raw data and calculations can be downloaded here. The targets are shown at the end of this post. Summary analysis:

Precision of KIDD vs Feddersen rifles on different ammunition
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XCR Short-barrel Precision

XCR equipped with a precision stainless 11

A precision-obsessed friend was lamenting the apparent inability of his Robinson XCR to shoot tight groups. Although it was not designed specifically for precision, I am a fan of the gun’s design. Particularly given its ease of changing barrels, I began to wonder how much we could improve on the standard chrome-lined light-contour barrels. So I sent two Lothar-Walther match-grade 1:8 rifled stainless steel blanks to Robinson and waited (seven months) for them to return as heavy-contour 11″ 5.56mm XCR barrels.

This is not a gun that is easy to shoot precisely: It is light, and its single-stage trigger breaks at over 4 pounds, which I know robs me of accuracy. In order to remove shooter dispersion from the equation I tested various configurations in a custom machine rest. I ran a range of ammunition through two standard 11″ barrels and, sure enough, 10-round groups would typically exhibit a mean radius in the vicinity of 1.5MOA. The standard 16″ light barrel, interestingly, printed 10-round groups with MR just above 1.0MOA shooting light bullets (both XM-193 and Wolf Classic!), but didn’t do as well with heavier bullets in match-grade loads (despite its 1:9 twist).

With the new precision barrels the rifle prints 10-round groups with mean radius consistently below 1.0MOA, like these:

XCR Precision 11

Note that from the short barrel 75gr .223 loads run about 2260fps. On the high end, 55gr 5.56mm clocked 2775fps.

There is some vertical stringing evident, which varies with the upper, and which suggests there is further room to tighten the design. And, as mentioned above, these groups were achieved with a machine rest. When I shoot off of bags 10-round groups open up by roughly another 0.5MOA. Suffice it to say that with a good barrel and shooter this gun is capable of respectable accuracy.


I recently supplemented my 6-year-old Sony Alpha-300 DSLR camera body with a mid-grade Sony A-77II SLT: a clever body that uses a fixed semi-reflective mirror instead of the moving mirror that dominated the field until the recent advent of mirrorless digital cameras. Though still stuck with the APS-C format this was an upgrade to a much more sensitive and higher resolution 24Mpx sensor (from the 300’s 10Mpx sensor). The other salient features are vastly improved auto-focus, imperceptible shutter lag, and a machine-gun fast 12fps continuous shooting rate.

The other upgrade I just made was to my lighting kit. Until now I have relied on natural light, reflectors, and a lone Sony 43GN speedlight. For this shoot I added two $60 Neewer TT 660 flashes, which despite their low price are fully featured for manual lighting and sport a Guide Number of 58. I also bought a cheap radio trigger system that is able to sync all three flashes up to 1/200s. The Neewers take two seconds for a full recharge from batteries, but dialing them back to 1/16 power they can keep up with full-speed shooting bursts.

For this shoot I relied almost entirely on the light from these three flashes on a 10′ x 6′ stage. At 1/4 power I could shoot 100 ISO f/6 at 1/200s. For the action sequences I had to reduce the flash power to keep up with the shooting rate, but that revealed another strength of the speedlights: lower power means faster discharge rates, so even leaving my shutter about 1/200s the effective exposure was in the neighborhood of a motion-freezing 1/1000s.
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Products I’m Looking For: 2015 Edition

Here’s my annual gift to entrepreneurs: If you want to make money, bring any one of these items to market and I guarantee you success!

More heavy subsonic .22LR ammunition. The market above 40gr is still limited to the Aguila 60gr load!

Gapless revolvers. The Nagant 1895 Revolver goes into battery when cocked to seal the cylinder gap. Revolver manufacturers pride themselves on their lockwork but the biggest innovation in revolvers in the 120 years since the Nagant went into service has probably been the shift of the barrel to the bottom of the cylinder with the Chiappa Rhino line. How about a revolver that is normally in battery and only cams out of battery to open or rotate the cylinder? Eliminating that loud, dangerous gap would be very cool, and doing it with a nice trigger pull would be a worthy achievement for a revolver engineer.

3-mode single/autoloaders. Historically automatic rifles have had a three-mode selector that toggles between Safe, Semi-automatic (one shot per trigger pull), and Automatic (typically either a 3-round burst or continuous fire while the trigger is depressed). For the civilian market that third mode has been eliminated. But there is another mode that would not be restricted that I would appreciate having in its place: Call it Manual, which would fire a loaded round but not cycle the action. The biggest benefit would be found shooting suppressed, where the option of keeping the action locked up would result in quieter shots and less fouling. The Manual mode would also be a useful tool for training. Granted, it is possible to run some piston guns in manual mode: the Ruger SR-556 and the XCR have gas selectors that can close the gas system completely. But they aren’t designed to be easily toggled the way fire control switches are.

Faster, cheaper, higher-resolution video cameras. As of now there is a gap between the $5500 Edgertronic, which can shoot 720p at 700fps and lower resolutions up to 18kfps, and (of all things) the $900 iPhone 6 which maxes out at 240fps in 720p. No camera in the consumer price range offers sustained video above 240fps!

Barrett REC7 Precision

Barrett REC7 with NF-F1 and LAR

We’ve been questioning what sort of precision we can expect from a piston-driven rifle with a chrome-lined bore. Those are both features believed to reduce accuracy (vs direct-impingement and an unchromed bore). We tested our Ruger SR-556 shooting ten-round groups using the same suite of ammo as in our Savage .223 Precision test and got CEP across the board about 1 MOA (with the exception of the bottom-of-the-barrel Wolf Classic, which produced CEP of 1.5 MOA).

This weekend we got a chance to try a little harder with a Barrett REC7, a premium rifle. Shown above, we fitted it for this test with an LRA bipod and NightForce F1 scope. Five shooters took 10 shots each with two different types of ammo. Given the conditions the shooter variation was minimal. The ammo makes the difference, and this gun sets a new precision benchmark for its type:

Load CEP (MOA) 90% Confidence
Federal Gold Medal Match 77gr 0.50 (0.45, 0.57)
American Eagle XM193 0.96 (0.86, 1.13)

Flash Rounds: Tracers Fired Backwards

Tracers loaded forwards and backwardsA traditional tracer bullet like the M62 carries an incendiary payload in its base. We’ve done a lot of experimenting with bullets fired “backwards” (i.e., base first), and found them to be both accurate and effective, even if their blunt shape produces excessive long-range drag.

TracerExplosionSo what happens when you fire a tracer base first? First of all, the tracer doesn’t ignite in flight. But if it hits something hard, like a rock or steel target, the jacket ruptures and the impact energy usually ignites the tracer compound all at once, producing a satisfying flash and puff of smoke, leading us to call them “flash rounds” or “smoke rounds.”

Once again our friends at Aimed Research provided a high-speed video of a flash round hitting a metal target:

Granted, these are nothing like a “true” incendiary round, which sounds like a cherry bomb exploding. Following is a video of a real incendiary bullet hitting the same metal target. It has a larger payload of fuel (magnesium and/or aluminum) and oxidizer (barium nitrate).