June 21st, 2008

New Tubb 111gr 6mm Bullets to Ship

Many readers have been asking: “When are the new 6mm plastic-tipped 111gr Tubb bullets going to be available?” Well, we talked to David Tubb, and he indicated the new DTAC 111-grain MJPT (Match Jacket Plastic Tip) bullets should start shipping next month. These bullets have a shorter bearing surface than the older DTAC 115s, so they should be more versatile, and not require rifles to be chambered with such a long throat. The Ballistic Coefficient, calculated on the bullet design, should be around 0.575. However, David notes that, as with all bullets, the exact BC is velocity-dependent.

CLICK HERE for DTAC 111 Information Sheet (.pdf file)

DTAC Tubb 111 bulletDavid predicts that this new bullet will be more accurate than the DTAC 115 — David’s testing showed superior overall performance from the slightly lighter-weight projectile. The 111 should also be easier to tune than the 115. The 111-grainer’s bearing surface is .015″ shorter than the 115. The jacket draw on the 111 is shorter than a 107 SMK. David says: “Shorter draw translates to better jacket consistency.”

The new 111gr bullet features a plastic tip. This, David believes, provides more consistent bullet-to-bullet BC — and tests by others support that view, so long as the tips themselves are uniform and properly attached. David says: “The typical out-of-the-box bullet could have a spread of 10% in true BC, from bullet to bullet. With the plastic tips you cut down the BC variance considerably. What we’ve seen in field testing is a spread of only 2% in actual bullet BC. This has reduced the shot-to-shot velocity spread as actually measured at long range.” When bullets maintain more uniform speed over the course of flight, you may see tighter groups with reduced vertical spread, all other factors being equal.

This new DTAC 111 MJPT will be available either “naked” or coated with Boron Nitride (BN). Call (806) 323-9488 for current pricing and to place an order. Visit www.DavidTubb.com for more details.

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June 21st, 2008

Timex Altimeter, Barometer, Thermometer Watch

Temperature, Atmospheric Pressure, and Altitude — all these things can and do affect bullet ballistics. Moreover, temperature changes can alter powder performance and chamber pressures. The smart reloader takes the predicted ambient temperature into account. And when calculating your come-ups and windage click values, you need to factor in Temperature, Air Pressure, AND Altitude.

Kestrel 4000 Weather TrackerHow do you keep track of these important variables when you’re shooting? The Kestrel 4000 Pocket Weather Tracker®, is compact and provides a wealth of information: atmospheric pressure, altitude, density altitude, temperature, humidity, wind speed, wind chill, dew point, and heat index. We like the Kestrels and recommend them. But at $279.00, a Kestrel 4000 is too expensive for many shooters.

Timex now offers a solution. For about $56.00-$80.00 street price, the Timex Expedition® Adventure Tech™ watch (item T41501EA) displays Altitude, Barometric Pressure, and Temperature (ABT). The thermometer function records temps from 14° F to 140° F. The Altimeter reads from -2,296 feet to +29,520 feet with 10-foot resolution. The Barometer tracks current and sea level pressure, and provides a graph of pressure changes over time.

Timex Altimeter Watch

Encased in a stainless housing with a resin band, the Timex watch is water resistant to 50 meters, and offers many other nice features, including dual time zones, countdown timer, alarm, and backlit nightlight (very handy).

There are other quality watches, such as the Suunto Core, that provide Altitude, Atmospheric Pressure, and Temperature read-outs. But, at under $70 street price, the Timex costs one-fourth the price of the Suunto. Amazon.com is currently offering the Timex Temp/Altitude/Barometer watch for $55.97 – $79.95 (depending on source). It is offered with a silver band as well as the black shown above.

Useful Tool or Just Another Gadget?
Is this watch really useful or just another piece of male jewelry? Well just last week a friend was developing loads for his PPC. While chronographing his loads he wanted to input the ambient temperature, and current air pressure in his log. We just had to guess on those numbers. It felt like 90°+, but it may have been in the mid-eighties. With the Timex we’d have had reliable data (Note: it’s best to take the watch off your arm when gauging air temp). For this editor, the Timex ABT watch is a useful tool. I bought one and will be using it during load development and when shooting competitively.

Here’s an owner’s review: “I have been through a Nike ABT, a Swiss Army ABT, and a High Gear ABT watch this year alone. None of them, which cost quite a bit more, have been as accurate and durable as this Timex. It has a better fit, was easy to use and read and just plain ‘on the money’ as far as forecasting weather and altitude. Also, I have not had to take it off my arm for 10-15 mins to get a decent temperature rating. It has always been within 1-3 degrees of actual temp. And I live in the Carribean in a tropical climate… so, for it to be this accurate is a statement in itself.”

And here’s an interesting comment from one purchaser: “I bought this watch to set the jetting on my racing go kart. I needed to know field elevation, and temperature. Plus changes in barometric pressure as the day went on. Most teams use a weather station and computer that cost over $700 for this purpose. My watch and accompanying chart (for the motor) has given me the same results.” If this watch works for racers, it can work for our “internal combustion” precision bullet-launching machines as well.

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