Designer SSK Industries
Case type Rimless, bottleneck
|Place of origin USA|
Parent case .338 Lapua Magnum
Bullet diameter .510 in (13.0 mm)
The .510 Whisper is a subsonic rifle cartridge developed by SSK Industries for use in suppressed rifles. It fires a .51-caliber bullet weighing 750 gr (49 g) at roughly 1,050 ft/s (320 m/s).
Despite the large bullet, this round is very quiet, similar to the noise from a .22 Short when used with a suppressor. When used with a very high ballistic coefficient bullet, the round only loses about 100 ft/s (30 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 and .300 Winchester Magnum. SAKO TRG-S test rifles have achieved MOA 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. Necessary components such as barrels, reloading dies, etc. are available from SSK. Sako 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-grain (62 g) bullets.
The case of the .510 Whisper is based on the .338 Lapua Magnum that has been trimmed down to a length of 1.875 in (47.6 mm) and necked-down to accept a .510 in (13.0 mm) diameter bullet. Neck wall thickness is reduced to 0.013 in (0.33 mm) and a small shoulder is cut into the body for headspacing. Overall length of the loaded round is about 3.34 in (85 mm).