Thread: Velocity/Powder question

Hello Reloading Gurus,

I am working on reloading for a 280 Ackley Improved Kimber Mountain Ascent rifle which is 24" barrel and twist rate of 9 - with a DPT Suppressor.

I am using Hornady 139SST 7mm projectiles and Nosler brass. I am using AR2209 powder and note that if I use 140gr projectiles, the starting load is 52.2grains @ 2,895fps and the max is 55.5grains @ 3,010fps.

I am using 54.5 grains AR2209 and expected (guessed as 139SST projectile isnt listed so went for 140gr) the velocity to be between 2900 and 3000fps with the 139gr SST projectile.

I tested with a chronograph yesterday and found out of 12 shots, the high was 2845fps, Low was 2775fps with 2820fps being the average. This was allot lower than I expected.

Just wondered if this velocity should be allot higher that what it actually was and if there is anything I should be looking for? Or is this normal and I shouldn't be concerned?

Cheers Alan