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Sunday, March 04, 2007

The Tactical Blog from Cactus Tactical

Long Range Shooting Secrets: Bullet Tips

The twist rate of the barrel determines the best bullet weight for your gun and is the single, most important factor for rifle accuracy . The manufacturer cuts the rifling to a twist rate that will stabilize the bullet designed and tested for that cartridge. The smaller the bore diameter, the more difficult it is to stabilize a bullet.  Heavy bullets cannot be driven to the same velocities as lighter bullets in the same barrel, so they are also not spinning as fast leaving the muzzle and may not stabilize down range.  Bullet spin is a product of twist rate and velocity.  A sure sign of a bullet not spinning fast enough is a target with oval or keyhole hits.  Using a light bullet in a fast twist rate barrel may cause the bullet to skip across the rifling and literally file itself, thus larger groups.  Excess copper residue in the barrel is a clue.  Try to duplicate factory loads.  They have been extensively tested for best results.  Matching the bullet weight to the twist rate and velocity is essential for accuracy.  If you need a heavier bullet than your twist rate will handle, you are probably using the wrong rifle. 

Bullet parameters: 
Besides weight, there are five measurements that should be considered when
selecting a bullet.  Sectional Density:  A weight to length ratio
measurement.  The longer and heavier the bullet, the higher the sectional
density thus the deeper it will penetrate.  This parameter is not important for
target and varmint loads but is very important for game hunting loads. 
Ballistic Coefficient
(BC):  The higher the BC, the more aerodynamic the
bullet, thus it will drop less at long ranges and will be less affected by cross
winds.  Due to air density, small diameter bullets such as a .224” typically
have poor BCs.  6mm bullets and larger start getting higher BCs.  A BC of .400 is considered very good, .500 and higher is excellent.  Balance:  All rifle bullets are heavier in the rear than the front and therefore are naturally unstable.  The more balanced, the more stable it will be.  Bore Surface is the length of the bullet that actually touches the bore.  The longer the bore surface, the more it dampens effects from bullet jump shock and the more stable the bullet will be going down the barrel.  This parameter is very important for accuracy.  Ogive is the point on the nose where the bullet first measures full diameter.  This important parameter will dictate bullet seating depth, bullet jump and cartridge overall length.  All bullets must be seated at optimum depth for best accuracy.  This usually occurs where the ogive is .010” from the rifled bore.

Conclusion: Analyze before loading.  Always stay within the bullet weight intended for your twist rate. Try to select a bullet with the longest bore surface, best balanced, shortest ogive to tip measurement, highest ballistic coefficient, and best sectional density, in that order. A good place to start is a boat tail with a blunt nose or hollow point. Most reloading manuals list BC, sectional density, and have pictures of bullets so you can compare important parameters. Don’t skimp on bullets; buy the best quality you can find.  Most bullets sold in bulk packs are not uniform weight. Stay with boxes of 100. Use a Bullet Depth Gauge to determine the exact bullet seating depth for each different bullet type. Bullet Depth Gauges are available from Cactus Tactical for all cartridges using .224, 7mm, and .308 diameter bullets.  These tools are very easy to use and come with simple instructions. Currently they are available for guns with direct in-line chamber access such as a bolt action, single shot, AR-15, etc.

This article is one in a series written by Gary Bunker,
Cactus Tactical's Master Gunsmith and rifle tuner.

About Cactus Tactical:

Cactus Tactical Supply
was formed in 1999 to support Phoenix, AZ customers with their tactical gear, CQB equipment, assault supplies and ammunition needs. They soon began serving local law enforcements agencies and military organizations as a natural extension of the original business charter. It was a small step after that to go nationwide via the Internet and provide a 24 hour web store to provide law enforcement officers, military personnel, tactical enthusiasts and the armed savvy civilian with a place to buy their tactical gear and equipment at reduced prices. Cactus Tactical carries many of the top brands of equipment designed to function effectively in hostile environments. The 24 hour Internet accessible web store currently displays over 3,000 individual items for immediate purchase.

The company is headquartered in Phoenix, Arizona, USA. For more information, log on to or call 877-9-CACTUS.

Shawn in the Korengal Valley, Kunar Province, Afghanistan.

For more info on these and other weapons
Technical specs compiled from:

"The appearance of U.S. Department of Defense (DoD) visual information does not imply or constitute DoD endorsement."


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