Pressure Traces: pn45: SR4759 Old v New Lots
Jun 16, 2011 18:58:58 GMT -5
Post by TGinPA on Jun 16, 2011 18:58:58 GMT -5
Pressure Traces: pn45: SR4759 Loads with Old v. New Powder Lots.
I am running out of my old metal canister lot of SR4759. The new lots which come in plastic containers are said to be different, requiring more powder to obtain the same velocities as from the old lot. From what I have seen quoted, 2-3 more grains more of the new lot is needed to equal what the old lot provided. To see what changes regarding pressures might occur, I traced old and new lots of SR4759 using a resized 300gr Rem jhp loaded sabotless.
Gage and Module Manufacturer = RSI USB model
Trigger Sensitivity = 0, Strain Gage Voltage =4.9 Gage Factor =2.1 PSI Correction Factor: 0
Barrel Temp = 72-76 degrees F. measured at the sensor (IR). Rifle Stand: Caldwell Lead Sled
Altitude: 450 ft Chronograph: Chrony Alpha Model 8 ft from muzzle. (13 fps. added to all recorded velocities to correct for distance of chrony from muzzle.)
Barrel Type: PacNor .45 Cal Muzzleloader Barrel OD = 1.06in. Barrel ID = .452in.
Breech Plug:Savage Std. (screw-in ventliner) ventliner orifice .032 in. Sensor dist fm BP=1.1in. Bullet Diam.= .458 resized to .448in.Type = 300 Rem jhp Bullet weight = 300gr. unknurled. Sabot: none Wads:Lubed wool over .462x.060 lubed fiber.
Powder: Panel 1: SR4759 metal canister 43gr 3shots.Panel2: SR4759 Plastic container 46gr. 3 shots.Panel 3: SR4759 Plastic container 50gr. 1 shot. Primer :Fed 209A
Shot fm. dirty barrel. These load seemed safe in my barrel under the test conditions but may not be so in other conditions.
Of interest was the small extreme velocity spread for both 3 shot traces, to be expected with relatively fast powders and relatively heavy bullets. Under the test conditions, the burn characteristics of the new SR4759 powder lot in plastic containers seem significantly slower than the older lot in metal canisters.. With the bullet tested, to obtain equal velocities required about 3gr. more of the new powder lot compared to the old lot, in agreement with previous observations. However, to obtain equal peak pressures in the 40kpsi range requires about 6gr. more of the new powder compared to the old lot. At these pressure levels with a 300rem jhp bullet, when powder loads are set so that peak pressures are matched, velocity is about 100fps higher with the new powder lot.
TG
I am running out of my old metal canister lot of SR4759. The new lots which come in plastic containers are said to be different, requiring more powder to obtain the same velocities as from the old lot. From what I have seen quoted, 2-3 more grains more of the new lot is needed to equal what the old lot provided. To see what changes regarding pressures might occur, I traced old and new lots of SR4759 using a resized 300gr Rem jhp loaded sabotless.
Gage and Module Manufacturer = RSI USB model
Trigger Sensitivity = 0, Strain Gage Voltage =4.9 Gage Factor =2.1 PSI Correction Factor: 0
Barrel Temp = 72-76 degrees F. measured at the sensor (IR). Rifle Stand: Caldwell Lead Sled
Altitude: 450 ft Chronograph: Chrony Alpha Model 8 ft from muzzle. (13 fps. added to all recorded velocities to correct for distance of chrony from muzzle.)
Barrel Type: PacNor .45 Cal Muzzleloader Barrel OD = 1.06in. Barrel ID = .452in.
Breech Plug:Savage Std. (screw-in ventliner) ventliner orifice .032 in. Sensor dist fm BP=1.1in. Bullet Diam.= .458 resized to .448in.Type = 300 Rem jhp Bullet weight = 300gr. unknurled. Sabot: none Wads:Lubed wool over .462x.060 lubed fiber.
Powder: Panel 1: SR4759 metal canister 43gr 3shots.Panel2: SR4759 Plastic container 46gr. 3 shots.Panel 3: SR4759 Plastic container 50gr. 1 shot. Primer :Fed 209A
Shot fm. dirty barrel. These load seemed safe in my barrel under the test conditions but may not be so in other conditions.
Of interest was the small extreme velocity spread for both 3 shot traces, to be expected with relatively fast powders and relatively heavy bullets. Under the test conditions, the burn characteristics of the new SR4759 powder lot in plastic containers seem significantly slower than the older lot in metal canisters.. With the bullet tested, to obtain equal velocities required about 3gr. more of the new powder lot compared to the old lot, in agreement with previous observations. However, to obtain equal peak pressures in the 40kpsi range requires about 6gr. more of the new powder compared to the old lot. At these pressure levels with a 300rem jhp bullet, when powder loads are set so that peak pressures are matched, velocity is about 100fps higher with the new powder lot.
TG
