I saw a barrel for my Encore. What's this round used for and is it worth fooling with? Seems like a likly subsonic round. Any thoughts are appreciated.

It was designed by SSK as a subsonic round to function in suppressed AR-15s as well as Contenders. Original loading was the 240 gr matchking at slightly under the speed of sound. Twist rate is critical (I think 1 in 8") as the 240 grain bullet depends on tumbling, not expansion for wound channel and killing power. It must be under-stabilized to work right. A lot of people forego the subsonic biz and shoot 125 to 130 gr bullets full speed.

The 300 Whisper was indeed developed as a subsonic round but has found popularity with the pistol silhouette crowd.

This round is used quite a lot by pistol silhouette shooters, especially in the Standing Unlimited category. It is shot with the more common 30 caliber bullets at higher speeds.It is an odd looking thing, the darned bullets are bigger than the cases.

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It makes for a good short to moderate range deer cartridge using the 150 grain nosler balistic-tip. It'll actually do 2100 ft/sec with that bullet in a 21" barrel. Using the subsonic loading it makes for a good backyard nuisance deer cartridge used by professional animal control people. At those ranges an easy neck shot will put the deer down on the spot. And it makes for a good kids cartridge.