Best Bullet Weight For Your Gun

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.

Bullet Weight
Bullet Weight
Cactus Tactical
Cactus Tactical

USA –  -(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 linked twist rate tool).

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 Weight Bullet Parameters:

Besides weight, there are five measurements that should be considered when selecting a bullet.

  1. 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.
  2. 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.
  3. 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.
  4. 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.
  5. 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.

Bullet Depth Gauge : http://goo.gl/jLkcOH
Bullet Depth Gauge : http://goo.gl/jLkcOH

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 bullets 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 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.

 

  • 6 thoughts on “Best Bullet Weight For Your Gun

    1. The chart above states that .308 cal. with a twist rate of 1-12 should use 168gr-170gr. If this is the best weight of bullet for these specs then why does the Marine Corps use 175gr for the M40A series of rifles? (These rifles have a 1-12 twist also).

      1. I have seen a few articles discussing optimal twist rate for barrels, and not all of them are very clear that the twist rate needed to stabilize a bullet depends on three primary factors: the caliber, the length, and the weight of the bullet. It does not depend on velocity, except that there be a reasonable amount, and it does not depend on the length of the barrel, although increasing barrel length does generally increase velocity and accuracy according to formulas not provided here. If a bullet is lighter, smaller in diameter, or longer, then the twist needs to be faster (fewer inches per twist) for gyroscopic stabilization, and the reverse is of course true for allowing a slower rotation per distance of travel. True, there are other minor factors, but, for example, when air temperature and the air density at different elevations change, that is not something for which you can adjust the twist in your firearm barrel!

        The faster a bullet spins, the more gyroscopically stable it becomes, but of course a faster than necessary rotation may also decrease velocity as energy goes into the spin and the barrel friction increases. The GyroStabilityFactor in the formula below indicates the degree of stability achieved. If GSF is less than 1.0, then the bullet is unstable. 1.0 to 1.5 is fair, 1.5 to 2.0 is good, 2.0 to 2.5 is great, and over 2.5 is high. If the formula is reorganized to deliver the best twist rate for a bullet, then it is usually suitable to plug in a value of 2.0 as the “standard” GSF.

        Here, then, I offer a formula in a format that can be rather easily copied and adapted to a spreadsheet. It is essentially Miller’s formula, slightly simplified to eliminate temperature and elevation. If you supply only three values and have the formula pick them up, then I believe you can throw away the various tables you may have seen and make your own if you wish, or just check the barrels that you are curious about for the bullets that you would like to use in them.

        GyroStabilityFactor=30*BulletGrains/(Caliber^3*(BulletLength/Caliber)*(1+(BulletLength/Caliber)^2)*(TwistLength/Caliber)^2)

        BulletGrains is the weight of the bullet in grains.

        BulletLength is the length of the bullet in inches.

        Caliber is the inch decimal diameter of the bullet. E.g., a 30-06 uses a .308 bullet.

    2. Don’t know were you plagiarized the twist rate info, and I have saw it on other sights. The rates are wrong plain and simple. That’s all I’ve got, except I would do a little bit better checking of ballistics, tables, charts, and plain old hard data before publishing any more of this rubbish!

      1. I agree, this is a load of crap.

        I have a .308 WIN with a 1:12. I use 155gr Nosler Custom Competition heads which I buy by the 1000s. I throw them out at 2500fps and they group 1/2 MOA consistently no questions asked.

        Please back your statements up with mathematical proof. Give me a formula which determines the figures you blurt out.

    3. I have a Ruger Mark 2 in a 223 with a 1:14 twist 22″ barrel . Trying to find a Copper bullet that will group well at 100 yards . 52gr lead shoots ok 1″ groups 100 yards but copper is another story I’ve tried 55gr Barns Vortex and 35 gr Nosler BTLF Trophy Grade Varmint 3″ groups 100 yards . A hand load will work send info Please help before the gun gets melted .

    4. Hi Mr!
      I am Bill from Greece and I have the Ruger American Compact rifle cal 308 win(length barell 18” and twist 1:10)
      What supersonic and subsonic cartridges(how grains?) should be used for I have very good accuracy?

      Regards from Greece
      Bill

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