I am using H4350 powder to load 140 GR Hornady BTHP Match bullets for a 26" heavy barrel in 260 Rem, and some recent results have me stumped. Here are the details:
Over a year ago I purchased an 8 LB keg of Hodgdon H4350, which has been opened six times to pour and return powder. The powder is stored in a cool, dry, cabinet inside an insulated garage. The space is climate controlled, and all cabinets have large silica gel packs to remove moisture.
2012 was spent developing loads for a rifle that was replaced at the end of the season. A month ago I began building loads for a new rifle, using 39.0 GR as a starting point to collect data before increasing the charge. 39.0 GR consistently produced 2661 FPS for me, after analyzing more than 40 rounds fired on two separate days.
So then I recently moved to 40.0 GR, and built 20 rounds for early data along with 20 more rounds at 39.0 GR. Yesterday was a warm day (finally reached 70F after months of 20-40F days), and I fired all 20 rounds behind the chronograph. I wanted a true comparison, so a string of five rounds at 39.0 GR charge were followed by five rounds of 40.0 GR... until all ammo was tested. To my surprise, every 40.0 GR round I fired delivered almost 80 FPS less than the rounds with 39.0 GR charge.
The powder still looks the same: dark, and smells of acetone. I've been careful to keep everything sealed tight and avoid moisture. What could cause this?
Over a year ago I purchased an 8 LB keg of Hodgdon H4350, which has been opened six times to pour and return powder. The powder is stored in a cool, dry, cabinet inside an insulated garage. The space is climate controlled, and all cabinets have large silica gel packs to remove moisture.
2012 was spent developing loads for a rifle that was replaced at the end of the season. A month ago I began building loads for a new rifle, using 39.0 GR as a starting point to collect data before increasing the charge. 39.0 GR consistently produced 2661 FPS for me, after analyzing more than 40 rounds fired on two separate days.
So then I recently moved to 40.0 GR, and built 20 rounds for early data along with 20 more rounds at 39.0 GR. Yesterday was a warm day (finally reached 70F after months of 20-40F days), and I fired all 20 rounds behind the chronograph. I wanted a true comparison, so a string of five rounds at 39.0 GR charge were followed by five rounds of 40.0 GR... until all ammo was tested. To my surprise, every 40.0 GR round I fired delivered almost 80 FPS less than the rounds with 39.0 GR charge.
The powder still looks the same: dark, and smells of acetone. I've been careful to keep everything sealed tight and avoid moisture. What could cause this?