The .510 Whisper was developed by SSK Industries to shoot .510 (.50 BMG

.50 BMG

The .50 Browning Machine Gun or 12.7×99mm NATO is a cartridge developed for the Browning .50 caliber machine gun in the late 1910s. Entering service officially in 1921, the round is based on a greatly scaled-up .30-06 cartridge...

) bullets in a suppressed rifle. The case is based on the .338 Lapua Magnum cut down to 1.885 inches (47.9 mm). Neck wall thickness is reduced to 0.013 inch (0.3302 mm) and a small shoulder is cut into the body for head spacing. Over all length of the loaded round is about 3.34 inches (84.8 mm) when using surplus bullets.

Overview

Despite the large bullet, this round is very quiet, similar to the noise from a .22 Short

.22 Short

.22 Short is a variety of .22 caliber rimfire ammunition. Developed in 1857 for the first Smith and Wesson revolver, the .22 rimfire was the first American metallic cartridge....

 when used with a suppressor

Suppressor

A suppressor, sound suppressor, sound moderator, or silencer, is a device attached to or part of the barrel of a firearm which reduces the amount of noise and flash generated by firing the weapon....

. And with a very high ballistic coefficient, the round has only lost about 100 ft/s (30.5 m/s) out to over 500 yards. This gives it more downrange energy at that distance than traditional .30 caliber rounds such as the .308 Winchester

.308 Winchester

The .308 Winchester is a rifle cartridge and is the commercial cartridge upon which the military 7.62x51mm NATO centerfire cartridge is based. The .308 Winchester was introduced in 1952, two years prior to the NATO adoption of the 7.62x51mm NATO T65...

 and .300 Winchester Magnum

.300 Winchester Magnum

The .300 Winchester Magnum is a popular, belted, bottlenecked magnum rifle cartridge that was introduced by Winchester Repeating Arms Company in 1963 as a member of the family of Winchester Magnum cartridges. The .300 Winchester Magnum is a magnum cartridge designed to fit in a standard length...

. SAKO TRG-S test rifles have achieved MOA

Minute of Angle

Minute of angle is the measurement of a ballistic round's deviation from its initial heading due to gravity and/or the effect of air resistance on velocity. Informally known as a "Bullet's Trajectory" or "the rainbow effect". Long range weapons must account for this effect because a fired round...

 and better accuracy with this cartridge at 600 yards.

Powders such as H110, 4227 or surplus WC820 are well suited for subsonic loads and give a low standard deviation

Standard deviation

Standard deviation is a widely used measure of variability or diversity used in statistics and probability theory. It shows how much variation or "dispersion" there is from the average...

. Necessary components such as barrels, reloading dies, etc are available from SSK. Sako

SAKO

SAKO, Limited is a Finnish firearm manufacturer located in Riihimäki....

 TRG-S actions are most often converted to this caliber. The Thompson Center Encore is also suitable, but is rather lightweight for shooting this heavy recoiling cartridge, especially when using 950 gr bullets.

See also

• Whisper Family of Firearm Cartridges
  Whisper Family of Firearm Cartridges
  The Whisper family of firearm cartridges is a group of wildcat cartridges developed in the early 1990s by J.D. Jones of SSK Industries. The Whisper Family was developed as a line of accurate, multi-purpose cartridges using relatively heavy rifle bullets for a given caliber in subsonic loads...
  
  
• List of rifle cartridges
• 12 mm caliber
  12 mm caliber
  This article lists firearm cartridges which have a bullet in the to caliber range.*Length refers to the cartridge case length.*OAL refers to the overall length of the cartridge.*Bullet refers to the diameter of the bullet....