August 11th, 2016

New DTAC 115gr Rebated Boat Tail Bullet from David Tubb

DTAC David Tubb 115 grain Sierra Rebated Boat tail bullet 0.620 BC

David Tubb has come out with a new, improved version of his heavyweight 6mm match bullet. David’s new DTAC 115gr 6mm projectile is very slippery — the tested G1 1000-yard BC is 0.620. The DTAC 115 features a Rebated Boat Tail (RBT) design and a factory-pointed tip (what David calls a “closed nose”). This bullet is in production now, priced at $145.00 for 500 bullets. David tell us “the new DTAC 115 has arrived” and his company is currently filling backorders. New orders will be taken at DavidTubb.com starting Monday, August 15th. You can also call 806-323-9488 (8:30 am-4:30 pm CT) to order.

David explained the two main reasons why the Rebated Boat Tail (RBT) design was chosen for the new DTAC 115 bullet:

1. It is easier to precisely hold tolerances when manufacturing the 7 degree boat tail angle. Most conventional boat tails have 9 degree angles (or greater).

2. The RBT more efficiently obturates to the bore of the rifle barrel when fired. (It mimics a flat base bullet design). This will allow the RBT design to extend your accurate barrel life by reducing gas leakage around the bullet when fired in a worn 6mm throat.

NOTE: David does NOT claim the RBT offers a higher BC compared to a conventional boattail design.

DESIGN FEATURES: DTAC 115 Bullet with Rebated Boat Tail

Commentary by David Tubb
In the 1980s we shot 107 grain weight-range 6mm bullets for Silhouette and High Power competitions. Lower recoil and good wind drift were paramount in coming to the 6mm bullet diameter.

DTAC David Tubb 115 grain Sierra Rebated Boat tail bullet 0.620 BCAfter I developed the 6XC case around 2003 I approached Sierra about making me a 6mm bullet in the 115 grain range. Sierra ran prototypes in 112, 115, and 120 grain configurations. I thoroughly tested these and decided on the 115 grain. In 2004 I used these at Camp Perry and the result was a Long Range National Championship Aggregate with a perfect 1450×101 score. Enough said….

In 2007 Sierra had just introduced its plastic-tipped bullets. I had them run a test batch of plastic-tipped 117 grain weights. These didn’t pass my criteria.

We then ran another test batch of 111 grain plastic tip 6mm bullets and they looked great in the Sierra tunnel tests. However when shot them over an Oehler 43 at 1000 yards the results indicated the plastic tips were deformed or nonexistent at the target. These didn’t pass my criteria.

FYI — that plastic tip deformation testing information preceded the Hornady “Plastic tips Are Bad” advertising campaign by more than seven years.

When using a .308 early in my High Power rifle career we shot 190 grain Sierras at the 600-yard stage. When 600-yard accuracy began to fall off a switch to a 185gr Lapua rebated boat tail brought the accuracy back. I remember shooting some very high X-Count scores with 185gr Lapuas. The reason the Lapua worked in a worn barrel is because the rebated boat tail allows the bullet to obturate to fit the worn throat and prevent less gas leakage around the bullet when fired.

I had a bullet-maker friend reform some 6mm 115s with a rebated boat tail (RBT) in 2015 and had excellent results. So it was a natural move to redesign the current DTAC 115 6mm with a RBT and a 7 degree boat tail.

Ballistic Coefficent and Stabilization

High BC Confirmed
David says, “The new DTAC 115 RBT testing is complete and [we] can claim a G1 1000-yard BC of 0.620″.

Required Twist Rate for Stability
David reports: “This bullet stabilized out of true 1:8″ twist or faster barrel at velocities approaching 3000 fps at sea level”.

Permalink Bullets, Brass, Ammo, New Product 7 Comments »
August 11th, 2016

Danger of Defective Primers — Primer Pocket Blow-Through

Primer Blown Gas defect winchester casehead

Think you can “get by” without protective eyewear? This story provides yet another example of why you should wear safety glasses every time you go shooting. You only have one set of eyes — they are much too precious to risk.”

Bad Primer Blasts Gas Through Side of Casehead
Our friend Grant Guess recently had a “close encounter” with a bad primer. An apparently defective primer caused part of the casehead on one of his rounds to blow out. This, in turn, allowed high pressure gas to vent through the damaged primer pocket. Take a good look, boys and girls. This is yet another very good reason to wear safety glasses. The cartridge was a 6.5-06, hand-loaded in necked-down Winchester-headstamp .270 Win brass. Grant reports:

“I had a blow-through between the primer and the primer pocket today. The action was really smoking and I got a face full of gas. This was a reasonably light charge. Thank God for safety glasses.

I should also mention that it appears there is a 3/64 hole that is halfway between the primer and the primer pocket. Like it burned a small jet hole through both of them.”

Could this happen to you? It just might. On seeing this damaged case, one of Grant’s Facebook friends, Chris D., observed: “Search the internet, you will see a lot of these pin hole ‘in the corner’ failures. Obviously Winchester has some issues with the LR primers.”

Careful Examination Reveals Apparent Primer Defect
After this incident, Grant examined the damaged case: “I pinned the flash hole and it is not over-sized or under-sized. The primer clearly has an area where it had a defect. At [50,000 CUP], it doesn’t take much of a defect to cause issues. There was a slight bit of pucker-factor on the next shot….”

Primer Blown Gas defect winchester casehead

Permalink Bullets, Brass, Ammo, Tech Tip 5 Comments »
August 11th, 2016

New Reactive Spinning Diamond Targets from Birchwood Casey

Here are cool new reactive metal targets that spin rapidly when hit (watch video above). Birchwood Casey’s new Diamond Spinning Targets are fun to shoot. And, after each hit, the diamond automatically resets to face the shooter. That’s handy. There are three versions — all feature a durable metal frame that’s easy to place in the ground

Choose the Jack, King, or Ace of Diamonds depending on your intended use (and type of guns):

Jack of Diamonds (for Airguns up to 1000 fps) — $37.00 MSRP ($26.83 from Amazon)
King of Diamonds (for .22 Rimfire pistols and rifles) — $41.00 MSRP ($33.41 from Amazon)
Ace of Diamonds (AR500 Steel for Centerfire pistols and rifles) — $140.00 MSRP ($73.25 from Amazon)

The Ace of Diamonds™ is constructed of ½” AR500 steel. That’s tough enough for centerfire handguns and rifles. The King of Diamonds™ is designed for .22 rimfire pistols and rifles. The least expensive variant, the Jack of Diamonds™, is rated for airguns up to 1000 fps. These Diamond Spinning Targets are made in the USA. For more info, visit www.birchwoodcasey.com or call 800-746-6862.

Permalink New Product, Shooting Skills No Comments »