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Best Bullet Weight For Your Gun
Cactus Tactical – Long Range Shooting Secrets. This series of Shooting and Gun Smithing Tips is brought to you by Cactus Tactical, an AmmoLand Expert Author

Cactus Tactical

Cactus Tactical - -(AmmoLand.com)- The twist rate of the barrel determines the best bullet weight for your gun and is the single, most important factor for rifle accuracy (see included twist rate chart). 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 proper bullet seating depth. Bullet Depth Gauges are available from Cactus Tactical in all cartridges with .224, 7mm, and .308 diameter bullets. These tools are very easy to use and come with simple instructions. Unfortunately, they are only available for guns with direct in-line chamber access such as a bolt action, single shot, AR-15, etc.

Rifle Twist Rates
Caliber – Twist Rate – Bullet Weight
.172
1:10 all weights
.222 Rim Fire
1:16 all weights, lead bullets

.224 / 5.56mm
1:16 up to 55 grains, 4300 fps or more
1:15 up to 55 grains, 4100 – 4300 fps
1:14 up to 55 grains, less than 4100 fps
1:12 55 – 63 grains
1:9 63 – 70 grains
1:8 70 grains or more

.243 / 6mm
1:15 up to 70 grains
1:14 70 – 75 grains
1:13 75 – 85 grains
1:12 85 – 100 grains
1:10 100 grains or more

.257
1:14 up to 70 grains
1:13 70 – 80 grains
1:12 80 – 90 grains
1:10 90 – 100 grains
1:9 100 grains or more

.264 / 6.5 mm
1:9 up to 130 grains
1:8 130 grains or more

.270
1:10 all weights

.284 / 7mm
1:11 up to 140 grains
1:10 Magnum velocities
1:9.5 140 grains or more

.308 / 7.62mm
1:15 up to 150 grains
1:14 150 – 168 grains
1:12 168 – 170 grains
1:10 170 – 220 grains
1:8 220 grains or more

.311 / 7.65 mm
1:10 all weights

.321
1:16 all weights

.323 / 8mm
1:10 all weights

.338
1:10 all weights

.348
1:12 all weights

.358
1:12 all weights

.375
1:12 all weights

.411
1:14 all weights

.416
1:14 all weights

.429
1:38 all weights

.458
1:20 all weights up to 2000 fps
1:14 all weights above 2000 fps

About Cactus Tactical
Cactus Tactical Supply was formed in 1999 to support Phoenix, AZ customers of various firearms training facilities with their tactical equipment and ammunition supplies. 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 allow law enforcement officers, military personnel, tactical enthusiasts and the armed savvy civilian to buy their equipment at reduced prices. Expansions into mail order and store front customer capabilities have followed over the last few years. Cactus Tactical carries most of the top brands of equipment that are designed for hostile environments. The internet accessible web store currently displays over 3,000 individual items for immediate purchase.

Cactus Tactical is headquartered in Phoenix, Arizona, USA. For more information on Cactus Tactical and Cactus Tactical products, log on to www.cactustactical.com or call 602-441-3924.

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Rifle Chambers Explained
Cactus Tactical – Long Range Shooting Secrets. This series of Shooting and Gun Smithing Tips is brought to you by Cactus Tactical, an AmmoLand Expert Author

Cactus Tactical

Cactus Tactical - -(AmmoLand.com)- The Small Arms and Ammunition Manufacturers Institute (SAAMI) was established to standardize case and chamber specifications. These specifications insure any ammunition produced for a given cartridge will fit and function safely in any firearm chambered for the same cartridge. As with any manufacturing process there are always variations due to tool wear, equipment alignment, and material differences. SAAMI specifications are actually pretty loose, especially for chamber dimensions. All rifle barrels, bar none, have variations in their chambers, even high dollar custom barrels. Even though the barrels are “in SAAMI spec”, the variations can mean the difference of 5 minute of angle (MOA) accuracy with the same ammunition in different guns.

To overcome these variations, shooters have to tailor their own loads. Unfortunately, reloading manuals don’t address chamber variations because they too have to follow SAAMI specs with case dimensions, bullet seating depth, and cartridge overall length. By measuring the rifle’s chamber, reloaders can trim brass for best fit and seat bullets at optimum depth. Bullet seating depth and brass length have a profound impact on accuracy. Most chambers are cut with too much “free bore”. This dimension is the distance from the rifled bore to where the shoulder starts. The free bore is at least .025″ larger than the bullet diameter and up to .100″ deeper than needed. As the bullet jumps from the case to the bore, it has room to move laterally resulting in less than perfect bore alignment. This causes the bullet to strike the bore off center and be deformed. As the deformed bullet travels down range, it actually wobbles a little. The greater the wobble, the worse the accuracy. Compensations for chamber variations can be made in the reloading process.

Case Neck Length Gauge.

First, measure the chamber case neck length using a Case Neck Length Gauge. After you measure the case length, trim your brass .005″ shorter than the measurement. This will allow room for the brass to “grow” when fired. Recommended SAAMI trim length is usually way too short for most chambers.

Bullet Depth Gauge

Second, you need to know the exact bullet seating depth to compensate for forward bullet jump. A long established fact: the less the bullet jump, the better the accuracy. Different bullet styles, shapes, and weights, will require different seating depths. Use a Bullet Depth Gauge to determine the exact bullet seating depth for each different bullet type. The bullet should be .010″ from touching the bore. If the bullet touches the bore, chamber pressure may increase.

Once you have worked up a load, use the above techniques to improve accuracy. Case Neck Length Gauges and Bullet Depth Gauges are available from Cactus Tactical in all cartridges with .224, 7mm, and .308 diameter bullets. These tools are very easy to use and come with simple instructions. Unfortunately, they are only available for guns with direct in-line chamber access such as a bolt action, single shot, AR-15, etc.

About Cactus Tactical
Cactus Tactical Supply was formed in 1999 to support Phoenix, AZ customers of various firearms training facilities with their tactical equipment and ammunition supplies. 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 allow law enforcement officers, military personnel, tactical enthusiasts and the armed savvy civilian to buy their equipment at reduced prices. Expansions into mail order and store front customer capabilities have followed over the last few years. Cactus Tactical carries most of the top brands of equipment that are designed for hostile environments. The internet accessible web store currently displays over 3,000 individual items for immediate purchase.

Cactus Tactical is headquartered in Phoenix, Arizona, USA. For more information on Cactus Tactical and Cactus Tactical products, log on to www.cactustactical.com or call 602-441-3924.

Brought to you by - AMMO LAND.COM – The Free Press Release Service for the Shooting Industry! www.AmmoLand.com .

Submit Gun, Ammo and Shooting Related News at Ammo Land.com .

Filed under: Featured Articles, Firearm News, Shooting Industry News by Ammoland No Comments »