July 23rd, 2013

Over-Stabilization of Bullets — Why Is Too Much Spin a Problem?

spinning bullet stabilizationOn the Applied Ballistics Facebook page, Ballistician Bryan Litz regularly offers a “Tuesday Trivia” question about ballistics. Today’s brain-teaser is a true/false question about bullet stabilization. On shooting forums you often find heated arguments about “over-stabilization”. Bryan wants readers to consider the issue of over-stabilization and answer a challenge question…

Is This Statement TRUE or FALSE?

“The problem with ‘over-stabilizing’ a bullet (by shooting it from an excessively fast twist rate) is that the bullet will fly ‘nose high’ on a long range shot. The nose-high orientation induces extra drag and reduces the effective BC of the bullet.”

True or False, and WHY?

Click the “Post Comment” link below to post your reply (and explain your reasoning).

Bullet Movement in Flight — More Complicated Than You May Think
Bullets do not follow a laser beam-like, perfectly straight line to the target, nor does the nose of the bullet always point exactly at the point of aim. Multiple forces are in effect that may cause the bullet to yaw (rotate side to side around its axis), tilt nose-up (pitch), or precess (like a spinning top) in flight. These effects (in exaggerated form) are shown below:

spinning bullet stabilization

Yaw refers to movement of the nose of the bullet away from the line of flight. Precession is a change in the orientation of the rotational axis of a rotating body. It can be defined as a change in direction of the rotation axis in which the second Euler angle (nutation) is constant. In physics, there are two types of precession: torque-free and torque-induced. Nutation refers to small circular movement at the bullet tip.

Diagram from the University of Utah Health Sciences Library Firearm Ballistics Tutorial
Permalink Bullets, Brass, Ammo 26 Comments »
July 23rd, 2013

Airglide Drop-In Rifle Cases on Sale with Free Shipping

The popular vertical-loading Airglide rifle case from Plano is on sale again. You may want to strike while the price is right. Amazon.com is offering the Plano Airglide for $42.95 with FREE shipping. Free shipping is important as transport fees add $10-15 to the price with many vendors. CLICK HERE to order from Amazon with FREE shipping.

Among injection-molded rifle cases, Plano’s AirGlideā„¢ case is unique in holding a rifle vertically, in foam cradles. This allows ample room for the 3″-wide fore-ends on BR and Varmint rifles. The foam blocks front and rear can even be trimmed for a custom fit, and velcro webbing straps hold the rifle securely.

Plano Air-Glide Rifle Case

Airglide Will Hold a Benchrest Rifle with Wide Fore-end and 28″ Barrel
Measuring 51 1/2″L x 7 3/4″W x 12 1/4″H, the AirGlide can easily handle rifles up to 50″ in length. That should hold BR rifles with barrels up to 28.5″ (or 28″ if you have a thick recoil pad). With its 27.5″ barrel, my 6BR is exactly 49″ long (including pad) and there is about 1.3 inches to spare in an Airglide. My 6BRDX (in a Tracker ST-1000 stock with a thin metal buttplate) has a 29″ barrel and it fits. If you have a real long barrel or extended buttpad, measure the gun first. The AirGlide has proven very popular with Varmint shooters and BR competitors. Lockable and airline-approved, the AirGlide is a unique product at an affordable price. This Editor owns three Airglides and they are my favorite cases for transporting wide-stocked rifles to the range. (For airline transport, I do prefer a heavy-duty, wheeled aluminum safari case with recessed locks.)

Plano Air-Glide Rifle Case
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July 23rd, 2013

Store Ammo (and More) Underground in MTM Survivor Container

Survivor underground ammo container can MTMIn-Ground Storage
With the price of ammo at all-time highs, folks are looking for ways they can stash ammo reserves securely, without using up precious space in their gunsafes. Additionally, there are important reasons why a locked, steel-walled gunsafe is not recommended for long-term ammo storage (see local fire regulations on the subject of ammo storage). MTM CaseGard now offers a heavy-duty, drum-style PVC container for underground storage of ammunition or other important items.

MTM’s Survivor Ammo Container features a rugged, bucket-style body with a double-O-Ring sealed lid and protective outer cap. The inner lid is held down with multiple screws to provide a secure seal. Then the larger “mushroom head” top fits in place over the whole assembly. Each container includes a heavy-duty Vapor Corrosion Inhibitor (VCI) plastic bag plus a moisture-absorbing desiccant pack. The 13.5″ x 10″ drum costs $22.10 at Midsouth Shooter’s Supply. That’s less than the cost of a box of bullets these days. Internal capacity is equivalent to a .50-Cal metal ammo can. The MTM Survivor will hold up to 600 rounds of .45 ACP or 223 ammo. It can also hold about 15-20 AR-15 magazines.

Survivor underground ammo container can MTM

Outside Dimensions: 13.5″ (H) x 10″ (D) | Inside Dimensions: 12.4″ (D) x 7″ (H)

This is a convenient way to hide ammunition, bullets, copies of important documents, emergency money, coins and other small items. Just make sure of two things. First, remember exactly where you buried your Survivor container. You may want to include a small notation on a site plot that you place in a safe-deposit box or give to trusted family members. Second, don’t just dig a hole, drop the unit in the ground and shovel some fresh dirt over the top. Restore a “natural look” to the vegetation or ground cover over the hole. Otherwise your prominent round dirt pile may attract unwanted attention.

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