Good Evening All
I would welcome thoughts on a loading dilema I have. I have a Sauer Drilling (c. 1945) which is chambered in 16b and 8x57JR (.318 inch). I have some of the Sellier & Bellot Factory ammunition loaded with the 196gn Soft Point. However, there is no non-toxic factory loading available, so I am developing a load with the Fox 150 gn Classic Hunter seated at a depth of 11mm. The powder is RS52 with a starting load of 46.4, which GRT predicted would give a MV of about 2600.
However, when I measured the first 3 shots with the Chrono, the average MV was 2440. This is quite a bit lower than I was expecting based on GRT so I took pause to research the possible causes. I haven't yet slugged the bore or measured distance to the lands, but I think I have a decent amount of free bore and have not had any issues with the factory ammo.
RS52 seems to be well calibrated based on the GRT indicator, so I am a little surprised that it is so far out. I put the chrono data into GRT, recalibrated and updated the K and Ba variables, but this gave me a "low burn rate" warning that I may get inconsistent results. I do not need to have a very fast load as this is not a long range rifle, but I am a bit concerned that the pressure may be TOO low and I am aware that low pressures can cause pressure spike issues (although I believe this is more prevalent with slower powders).
I put higher charge weights into GRT and was still getting "low pressure" warnings up to about 49gn. I am not at all keen to push the loads/pressures with an old gun (albeit in excellent condition), particularly as Drilling barrels are so thin(!) so I am somewhat unsure about what to do.
My best guess is that even though initial pressures may be high in the case due to the deep seating, the result is that the long free bore means bullet a good run at the lands and so the subsequent resistance (and pressure) are lower. But would this explain 160 fps difference to the model?
Even if the re-calibrated powder model might suggest a higher load is ok, I don't want to go above the max of the more conservative model.
Thoughts and suggestions would be very welcome.
Jimbozki
I would welcome thoughts on a loading dilema I have. I have a Sauer Drilling (c. 1945) which is chambered in 16b and 8x57JR (.318 inch). I have some of the Sellier & Bellot Factory ammunition loaded with the 196gn Soft Point. However, there is no non-toxic factory loading available, so I am developing a load with the Fox 150 gn Classic Hunter seated at a depth of 11mm. The powder is RS52 with a starting load of 46.4, which GRT predicted would give a MV of about 2600.
However, when I measured the first 3 shots with the Chrono, the average MV was 2440. This is quite a bit lower than I was expecting based on GRT so I took pause to research the possible causes. I haven't yet slugged the bore or measured distance to the lands, but I think I have a decent amount of free bore and have not had any issues with the factory ammo.
RS52 seems to be well calibrated based on the GRT indicator, so I am a little surprised that it is so far out. I put the chrono data into GRT, recalibrated and updated the K and Ba variables, but this gave me a "low burn rate" warning that I may get inconsistent results. I do not need to have a very fast load as this is not a long range rifle, but I am a bit concerned that the pressure may be TOO low and I am aware that low pressures can cause pressure spike issues (although I believe this is more prevalent with slower powders).
I put higher charge weights into GRT and was still getting "low pressure" warnings up to about 49gn. I am not at all keen to push the loads/pressures with an old gun (albeit in excellent condition), particularly as Drilling barrels are so thin(!) so I am somewhat unsure about what to do.
My best guess is that even though initial pressures may be high in the case due to the deep seating, the result is that the long free bore means bullet a good run at the lands and so the subsequent resistance (and pressure) are lower. But would this explain 160 fps difference to the model?
Even if the re-calibrated powder model might suggest a higher load is ok, I don't want to go above the max of the more conservative model.
Thoughts and suggestions would be very welcome.
Jimbozki
