November 1st, 2019

Ogives, Meplats, Boat-Tails and Other Bullet Design Elements

Bullet Design Zediker

Noted gun writer Glen Zediker (author of Top Grade Ammo), regularly contributes tech articles to the Midsouth Shooters Blog. One of Glen’s Midsouth Blog articles covers Bullet Design. We suggest you read the article — even seasoned hand-loaders will learn a few things about projectile properties (and how to choose the right bullet design for your needs). Glen also wrote a recent Blog article on cartridge pressure signs, linked below

Read Zediker Bullet Design Article | Read Zediker Pressure Signs Article

Glen explains: “A ‘match’ bullet’s job is to perforate a piece of paper. A bullet designed for varmint hunting, on the other hand, is designed to produce explosive impact, and one for larger game hunting strives to strike a balance between expansion and penetration. However! No matter how it’s built inside, there are universal elements of any bullet design, and those are found on the outside.”

Bullet Design Zediker

In his article, Glen identifies the key elements of a bullet and explains how they are defined: “Base, that’s the bottom; boat-tail, or not (flat-base); shank, portion of full-caliber diameter; ogive, the sloping ‘nosecone'; tip, either open or closed (open it’s called the ‘meplat’). The shape of the ogive and the first point of ‘major diameter’ are extremely influential elements. The first point of major diameter can vary from barrel brand to barrel brand because it’s the point on the bullet that coincides with land diameter in the barrel — the first point that will actually contact the barrel as the bullet moves forward. When there’s a cartridge sitting in the rifle chamber, the distance or gap between the first point of major diameter and the lands is called ‘jump’, and, usually, the less there is the better.”

Bullet Design Zediker

Ogives Analyzed — Tangent vs. Secant Bullet Designs
Glen notes that bullet designs reflect secant or tangent profiles, or a combination of both: “The two essential profiles a bullet can take are ‘secant’ and ‘tangent’. This refers to the shape of the ogive. A tangent is a more rounded, gradual flow toward the tip, while a secant is a more radical step-in, more like a spike. Secants fly with less resistance (less aerodynamic drag), but tangents are [often] more tolerant of jump [or to put it another way, less sensitive to seating depth variations].”

Glen adds: “Ogives are measured in ‘calibers’. That’s pretty simple: an 8-caliber ogive describes an arc that’s 8 times caliber diameter; a 12-caliber is based on a circle that’s 12 times the caliber. The 8 will be a smaller circle than the 12, so, an 8-caliber ogive is more ‘blunt’ or rounded. Bullets with lower-caliber ogives are more tolerant of jump and (usually) shoot better, easier. Higher-caliber ogives [generally] fly better, farther. This is an important component in the ‘high-BC’ designs.”

Learn More in Zediker Books
Glen has authored a number of excellent books for hand-loaders and competitive shooters. Here are three of his most popular titles, including his latest book, Top Grade Ammo:

zediker book glen top grade ammo zediker book glen top grade ammo zediker book glen top grade ammo

All these titles are available from Midsouth Shooters Supply. Click each cover above to purchase from Midsouth.

Permalink Bullets, Brass, Ammo, Reloading No Comments »
November 1st, 2019

Practical D.O.P.E. Video Offers Tips on Ballistics Data

In this NSSF Video, Ryan Cleckner, a former Sniper Instructor for the 1st Ranger Battalion, explains how to gather and organize D.O.P.E. (Data On Previous Engagements) and how to organize this information to make it readily available in the field. As the term is used by Cleckner, D.O.P.E. includes observed bullet drop information at various distances, as well as the effects of wind, temperature changes, humidity and other environmental variables.

If you know your muzzle velocity, and bullet BC, a modern Ballistics App should be able to calculate bullet drop with great precision at distances from 100-1000 yards — often within a couple 1/4-MOA clicks. However, because a bullet’s BC is actually dynamic (changing with speed), and because ballistics solvers can’t perfectly account for all variables, it’s useful to collect actual, verified bullet drop data.

It’s smart to start with ballistics data from a solver app, but, as Cleckner explains: “Odds are, you’re going to have to fine-tune that data to your gun and your system. Every scope and every rifle and every bullet [type] act differently. Your scope may not track the same from rifle to rifle, so it’s important you get the data that’s unique to you.” Cleckner also explains that the ballistic data supplied with some factory ammo may only give you a crude approximation of how that ammo will actually shoot through your gun.

drop chart scope coverKeeping Your Drop Data with the Rifle
Cleckner also offers some good advice on how to record D.O.P.E. on simple index cards, and how to keep your ballistics data with your rifle. This can be done with a laminated drop chart or data transferred to a scope cover (photo right). CLICK HERE, to learn more about creating handy field data cards.

At the 4:15 mark on the video, Cleckner shows a calibrated tape he has fitted around the turret of his riflescope. The tape shows distance numbers (e.g. “4” for 400 yards, “5” for 500 yards etc.) that correspond with the number of clicks (rotation) required to be zeroed at that particular distance. With that system, you simply “dial your distance” and your point of impact should equal your point of aim. It takes some skill (and the right software) to create these tapes, but the concept is great.

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November 1st, 2019

Tech Tip: Don’t Store Brass and Ammo Near Ammonia Solvents

Ammonia Solvent Brass Cracking MTM

Chances are that many of you have packed away your ammo and shooting supplies for the winter. Maybe you put your brass in a storage bin that might also contain solvents, old rags, or used bore swabs. Well, if you use any ammonia-based solvents, we suggest you separate the brass and ammo and keep it away from potential ammonia vapors. This is because long-term exposure to ammonia fumes can cause cracks to form in your brass. This can lead to case ruptures and possible injury.

This case-cracking phenomenon has been called Season Cracking, a form of stress-corrosion cracking of brass cartridge cases. Season cracking is characterized by deep brittle cracks which penetrate into affected components. If the cracks reach a critical size, the component can suddenly fracture, sometimes with disastrous results. If the concentration of ammonia is very high, then corrosion is much more severe, and damage over all exposed surfaces occurs. The brass cracking is caused by a reaction between ammonia and copper that forms the cuprammonium ion, Cu(NH3)4, a chemical complex which is water-soluble. The problem of cracking can also occur in copper and copper alloys such as bronze.

Season Cracking was originally observed by the British forces in India a century ago. During the monsoon season, military activity was reduced, and ammunition was stored in stables until the dry weather returned. Many brass cartridges were subsequently found to be cracked, especially where the case was crimped to the bullet. In 1921, in the Journal of the Institute of Metals, the phenomenon was explained by Moor, Beckinsale, and Mallinson. Apparently ammonia from horse urine, combined with the residual stress in the cold-drawn metal of the cartridges, was responsible for the cracking.

Ammonia Solvent Brass Cracking MTM
Don’t store ammunition (or brass) for long periods in a box or container holding ammoniated solvents:

The Australia Department of Defense (AUSDOD) has also explored the problem of brass cracking caused, at least in part, by exposure to ammonia. A study was done to see whether the amount of cracking (from ammonia exposure) varied according to the duration and temperature of the annealing process used on the brass. CLICK HERE to read AUSDOD Research Report.

Story idea from Boyd Allen. We welcome reader submissions.
Permalink Bullets, Brass, Ammo, Tech Tip 5 Comments »