Is 5.56mm “enough” bullet?

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Interesting suggestion here that the NATO-standard 5.56x45mm infantry cartridge was selected based on short-range engagements that prevailed prior to the proliferation of rugged magnified optics. I.e., since it was hard to see and hit an enemy more than a couple hundred yards away, the 5.56mm cartridge was considered adequate.

Ever since its adoption field reports have complained about its marginal stopping power. In recent years our military has spent a lot more time in wide battlefields with optics good enough to reach out to and beyond the nominal 400-yard “effective range” of the 5.56mm. It may weigh twice as much, but nobody questions the ability of 7.62 NATO to stop human targets out to 800 yards. (Beyond that is the realm of trained snipers, who may step up to .300 Win Mag or .338 Lapua Mag cartridges with effective ranges beyond a mile.) There has also been a lot of recent work on other cartridges that fit within the 5.56x45mm profile but provide better ballistics and stopping power, 6.8SPC being the most widely adopted of that family.

Update: As further evidence of 5.56 inadequacy at longer distances: One range I frequent hung steel plates at 600 yards using fire hose. One day I noticed several .223 bullets stuck in the hose nose first: After 600 yards of flight they retained so little speed they stopped in the first layer of rubber!

Steal This Gun Design!

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This is a photo of the Kel-Tec KSG: A brilliant bullpup pump-action shotgun with dual selectable magazines and capacity for 14 rounds. It was just announced in January 2011. Because it’s a bullpup it will be easier to handle than any conventional shotgun. The parallel magazine tubes make a “switch-to-slug” operation as easy as flicking the magazine selector. Everybody who wants a pump-action 12-gauge and can afford it will buy at least one of these.

I hope a company with more manufacturing capacity copies this design. Kel-Tec produces several ingenious guns but they have never been able to meet demand. I know dealers who have been on waiting lists for guns like the Sub2000 and RFB for years. Demand for the KSG will certainly be orders of magnitude greater than anything they have yet produced. Freedom Group, please steal this design!

[March Update: Never mind! UTAS has announced they will begin domestic production this year of the UTS-15, a bullpup shotgun very similar to the KSG. Advantages over the KSG apparently include locating the magazine tubes above the barrel (for better recoil control), round-count indicators, and the ability to automatically alternate tubes with each shot (to keep it balanced). A disadvantage appears to be that it ejects sideways. The South African NEOSTEAD is another similar bullpup pump-action shotgun, and the only thing keeping it out of the U.S. is the silly BATFE restriction on importing shotguns that are not sufficiently suited to “sporting purposes.”]

Corner Protectors

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Corner protectors aren’t just for homes with little kids running around constantly bumping into things: I have learned through painful experience that the sharp corners on melamine-coated fiberboard easily rip through fabric and skin.

I run a round-off router bit over all my exposed woodwork edges whenever possible, but with glued melamine and some finished furniture you can’t do that. A few years ago I found some soft plastic corner cushions that unobtrusively provided excellent protection against scrapes and dented foreheads.



Recently I built a bunch of new shelves with exposed corners that I wanted to soften and I spent weeks looking for the same corner protectors. It turns out that my preferred solution is also by far the cheapest of the many competing products ($3.50 for eight), and that these are available only at Babies R Us.
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Kohler BubbleMassage Bathtub Review

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I just remodeled two 18-year-old bathrooms. In one I replaced a cracking fiberglass tub with an American Standard Princeton “Americast” tub. I considered cast iron, but Americast is a durable porcelain-coated composite offering much better insulation against temperature and noise — not to mention being significantly lighter than cast iron.

The bigger project was our master bathroom, and when it came to finding a new bathtub I had several goals. I wanted something big enough for my 5’9″ wife to stretch out in, but not so big that it would never get used. I wanted a massage feature that didn’t use waterjets because of all the cleaning and hygiene problems associated with running bathwater through an enclosed pump system.

Kohler’s BubbleMassage line sounded like a good solution: These are acrylic tubs with 120 little holes around the base perimeter through which a motor blows heated air. After the bath is drained the motor blows any residual moisture out of the system to prevent mold growth.

A 6’x3′ drop-in looked like it would be the right size so I bought and installed a Kohler Mariposa BubbleMassage tub (just over $2000 from Home Depot). At 72 gallons to the overflow I thought that would be ample capacity for a luxurious bath.

It turns out things aren’t so simple.
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Not the Best Place for a Laser Sight

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Streamlight’s TLR weapon lights have long been popular handgun accessories. Indeed, a tactical gun should always be carried with a light source, and strapping a flashlight right to the gun makes sure you’ll never be armed but unable to positively identify a threat due to darkness.

I’ve raved before about the utility of laser sights, so I thought when manufacturers started combining lights with lasers it would be a synergistic win.

Glock with Streamlight TLR-2 light/laser-sightThe problem is that Streamlight and its competitors all went about this by tacking laser sights onto the bottom of their weapon lights. This is less than ideal because the light is already mounted under the barrel, so the laser ends up almost 2.5 inches from the bore of the gun it’s supposed to sight.

Granted, if you follow my instructions to always sight a laser parallel to the bore this just means that the bullet will hit 2.5″ above the laser at point-blank range, and that the Point-of-Impact (POI) will gradually converge on the laser before crossing below it. But I’m afraid many people are still tempted to zero their lasers for a specific range — say, 21 feet for a defensive handgun — and in that case the distance between bore and laser can cause very bad POI shifts for any other distance.

The following chart shows the Point of Impact relative to the laser for a bullet fired from the gun shown above. If the laser is sighted parallel to the bore then POI is within 2.5″ of the laser out to 50 yards. However if the laser was zeroed to match POI at 7 yards you can see that it is way off for longer ranges. For example, on a 30-yard target the bullet will already strike 10 inches below the laser indicator, and it goes rapidly downhill from there!

DirtFill.com

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I wanted to do some significant regrading of my lot. I calculated I would need about 700 cubic yards of additional earth to achieve my desired landscape. But going out and contracting for a company to haul and spread that amount of dirt would have run into the five figures.

Not only did I not have the budget for that, but I know that there are a lot of construction projects where contractors are paying sites to take dirt that they excavate. If you put out the word and wait long enough eventually you can make a mutually beneficial connection. One contractor pointed me to the information-age solution: DirtFill.com, an exchange where people trying to get rid of dirt can find others looking to take it.

I put a listing up there two months ago. Last week I got a call from a contractor who had done major excavations on a project just a few miles from me. I drove out to look at the dirt and found mounds of beautiful, clean fill. Their foreman followed me back to my site to look at the feasibility of disposing it. Two days later they drove a John Deere 410E into my back yard to spread and level the dirt as two tri-axles ran back and forth all day for the next three days.

My only expense was tipping the tractor operator to rip up some stumps and grade it just the way I wanted it. It was a win for them too because the next closest places for dumping were not only at least twice as far but were also charging to take fill.

Grout I Can Live With

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I have been busy renovating a house I recently bought. One of my biggest challenges has been coming up with bathroom surfaces that are impermeable and impervious to water and stains. Porcelain and ceramic tiles are a good start, but traditional tile grout absorbs water. Sealers can temporarily prevent that, but eventually grout lines are going to form a breeding ground for mold and mildew. My goal with all my construction is zero maintenance, maximum durability, and minimal effort to keep things clean.

For bathroom walls acrylic solid-surfaces are a good solution. The cheapest I could find are Swanstone and U.S. Marble, but those are still at least $20/sq.ft.

I was getting ready to go with vinyl for the floors when I started hearing mention of epoxy grouts, which are truly impermeable and never need sealing. Combining that with the $.77 square-foot porcelain tiles Home Depot was selling sounded like a winning combination. It took some research but here’s what I found:

Laticrete makes a patented epoxy grout called SpectraLOCK, which consists of a two-part epoxy cement (“Parts A and B”) and a third “Part C” sanded filler. Lowes is apparently the only retailer that carries SpectraLOCK, and they only stock the smallest “Mini” containers. A Mini is good for about 25 sq.ft. of tile but costs $23. For anything bigger it is better to go online and buy “Full” A-B units, which are equal to four Minis. The epoxy is the expensive part but it’s very light. StoneTooling.com delivers Full A-B units for $50. You can then go to Lowes and get 4 Part C containers in whatever color you want for $12.

Laticrete sells “Commercial” units of SpectrLOCK which are equal to 4 Full units. StoneTooling.com delivers Commercial A-B units for $150. Lowes doesn’t usually stock the 16 Part C containers you would need in a single color, so at that point you would either have to special order or pay to ship them.

Time to leverage real estate equity

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Bubbles and crashes in real estate over the last few years taught homeowners a few lessons: For one thing, don’t expose yourself to interest-rate or credit risks with exotic mortgages on your primary residence, unless you have liquid reserves to cover that debt if things go against you. For example, interest rates really can cause the cost of an ARM to go up. Balloon mortgages really do have to be paid off, regardless of how difficult it is to refinance when that time comes. And not only can the value of a home decrease, but there may even be periods when it’s impossible to sell for any reasonable price.

Lenders and owners of mortgage-backed securities learned a few lessons of their own, which for a time made it more difficult and expensive to take equity out of a home. However, most of them have by now taken their lumps and learned their lessons: No more liar loans, and no more rigged appraisals. The mortgage origination market is once again hot, and loans are being made at record low interest rates.

Government, the one entity that never seems to learn, is still out there subsidizing loans: not only via the tax credit for mortgage interest, but also through its patrons Fannie Mae and Freddie Mac (can you believe those are still around?). Consequently, if you have good credit this is the best time to leverage your home equity. Today’s WSJ article on the subject notes:

[P]eople who have a potentially profitable use for that money—preferably an investment—could come out ahead using this strategy. A borrower who takes out a mortgage at 4.5% is essentially borrowing money for free on an after-tax, after-inflation basis, assuming he is in the 33% marginal tax bracket and inflation returns to its long-term average 3% or more.

If you were thinking of moving to a better house this may be a doubly excellent time to do so: The higher end of the market was hit hardest and has been slowest to show signs of recovery. I am trading up to a better house that is selling below its build cost and, thanks to some aggressive mortgage shopping, I am financing the purchase with a 3.5%, zero-point, 5/1 conforming ARM.

Heavy Metals for Bullets

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As a preface to an upcoming series on subsonic rifles, I have compiled the following information regarding metals for bullets.

To produce good ballistics a bullet needs several characteristics.

  1. Internal: It has to remain solid at the temperature and pressures of firing, to avoid melting in the gun. It also must be softer than the barrel through which it is fired so that it conforms to the rifling of the barrel (which is critical to ballistic stability) and so that the barrel can be shot repeatedly without degrading.
  2. External: It should be as dense as possible, since density not only increases stability but also reduces the energy lost to air resistance during flight.
  3. Terminal: It needs to be tailored for some terminal objective. Depending on the target, we may want a bullet to explode, expand, penetrate, stop, or do some combination of those things.

Following is a list of elements that are of interest in meeting these objectives, ordered by density and noting their rough current cost:
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Sight in your Suppressor

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Summary: The most efficient baffle suppressors have internal asymmetries that can affect the flight path, and hence point of impact (POI) of bullets fired through them. Asymmetric suppressors can be “sighted in” to find the index that produces the most benign POI shift.

My first full-power rifle suppressor was Gemtech’s M4-02. I was baffled by its persistent tendency to not only double the size of my groups but also to drop them more than 3MOA from zero.

I have since learned that changes in point-of-impact (POI) when attaching a silencer to a rifle are considered normal. My first assumption was that POI shift was primarily due to changes in the barrel’s harmonics. So I spent a day trying to work up a load on my precision .223 bolt gun that would give me the same POI as my unsuppressed groups. I found loads that gave better groups with the suppressor, but they were still consistently 3MOA low. After some discussion with experts I concluded that harmonic changes are probably not the dominant source of POI shift, especially with thicker barrels.

Then I heard about AAC’s M.I.T.E.R. (Multi-Indexing for Targeting at Extended Range) System: A patent-pending suppressor and mount that allows the user to quickly change the index of the can in increments of 1/5th of a turn. AAC’s manual for the SPR silencer, which uses the MITER mount, has a helpful chart showing how rotating the can’s position can change the POI of groups. A review of this silencer even noted that POI shifts exceed 3MOA in some positions.

Asymmetric Blast BaffleWhy would changing the suppressor’s index reliably change the point of impact? It turns out that the most efficient baffle suppressor designs require asymmetries in the baffles to encourage the muzzle blast to redirect itself away from the bore line and into the baffles, instead of straight out the end of the can. If you look at the first “blast baffle” in such a can you will often see something like the divot shown in this photo. It is well known that the bullet isn’t the first thing out of the muzzle: The bullet pushes a column of air ahead of it, and as it leaves the muzzle the bullet is even overtaken briefly by the high pressure propellant gases behind it. As you sight in a silencer with an asymmetric blast baffle you will probably notice that the orientation of the divot correlates with the POI shift. So it appears that the divot is causing some of the propellant to nudge the bullet in a consistent direction.

How can you “sight in” your asymmetric suppressor? Essentially you want to shoot groups as you slowly change the orientation of the can around a full 360 degrees. But you should never shoot a silencer that isn’t fully tightened down. For sighting in my 1/2″-28TPI suppressors I bought this bag of very thin steel washers to allow me to shim it out roughly a fifth of a turn at a time. After zeroing I shot five-shot groups at each orientation, using two different types of bullets: flat-based 55gr, and boat-tailed 69gr. The resulting group centers and sizes are depicted in the following chart (which links to a spreadsheet with the raw data).

Obviously with my heavy barrel the orientation of this silencer is a critical factor in POI shift. Adding two shims before screwing on the can gives me groups that are only half an MOA from the bare barrel’s zero, with impacts just a little high. (With no shims this can produces the 3-4MOA drop shown on the chart.)
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