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After the discussions on the board about pressures and seating depths, I thought I would share my recent experience with load development on another rifle of mine, a Remington 700 in 22-250.
I had developed a load for this rifle a couple years ago which had served me well, but I was ready to work up a new load with a lighter bullet, recently. The old load was a 55 gr VMax, and I wanted to try the 40 gr VMax as a faster varmint pill. With this new bullet, I chose to go with 8208 instead of the Varget I'd run behind the 55 gr Vmax, and last week a very good accuracy node was found at 35 grains, significantly less than the Hornady published max for this setup.
This week, I ran several over the chronograph to ensure I had a solid load, with good SD, etc. When loading them up, I came across the remnants of a bag of new, unfired brass of the same manufacture as the cases I had developed the load with. I took this opportunity to test something I'd heard about, but had never personally quantified. I loaded 10 rounds using the new Winchester cases, and 30 more from the same lot of Winchesters which had been fired 4 times. All other variables were exactly the same - powder charge, pill, primer and seating depth. I also ran the new cases through the FL sizing die as a preparatory measure.
At the range, I first chronographed 20 rounds of the 4x cartridges and got my numbers. The avg MV was 3850 fps, with a 23fps SD. Not great but acceptable.
Next, I fired the rounds loaded with the new, unfired brass. At the first shot, I saw something was up. It chrony'd at 4195 fps, a full 245 fps faster! Knowing my Shooting Chrony occasionally got squirrely, I took note, checked the case for pressure signs (none seen) and continued shooting. Every subsequent shot came in as fast or faster, averaging at 4215 fps, for an overall increase of 335 fps!!!
This was also reflected downrange, as the group had opened significantly, and the POI had shifted 1/2 inch.
Summary:
While I recognize that different case manufacture is cause to redevelop a load, even when manufacturer is the only thing that changes, I did not expect the magnitude of the change I witnessed today when the brass was from the same manufacturer and lot #. I understood that new brass expands when fire formed in a given chamber (in this case, a Remington), but for the virgin brass to have so much less case volume is astonishing.
I acknowledge that with the Grendel, case volume is significantly less than the 22-250, and the usable bullet weights are quite far apart (~50 - 100 grains). Consequently, the effects on a Grendel's MV would likely be less noticeable. That being said, I suspect that any load developed using fire formed brass that is pushing pressures close to the maximum could likely go beyond safe limits, if new cases were introduced without first fire forming them at lower charge weights.
What say the Horde?
I had developed a load for this rifle a couple years ago which had served me well, but I was ready to work up a new load with a lighter bullet, recently. The old load was a 55 gr VMax, and I wanted to try the 40 gr VMax as a faster varmint pill. With this new bullet, I chose to go with 8208 instead of the Varget I'd run behind the 55 gr Vmax, and last week a very good accuracy node was found at 35 grains, significantly less than the Hornady published max for this setup.
This week, I ran several over the chronograph to ensure I had a solid load, with good SD, etc. When loading them up, I came across the remnants of a bag of new, unfired brass of the same manufacture as the cases I had developed the load with. I took this opportunity to test something I'd heard about, but had never personally quantified. I loaded 10 rounds using the new Winchester cases, and 30 more from the same lot of Winchesters which had been fired 4 times. All other variables were exactly the same - powder charge, pill, primer and seating depth. I also ran the new cases through the FL sizing die as a preparatory measure.
At the range, I first chronographed 20 rounds of the 4x cartridges and got my numbers. The avg MV was 3850 fps, with a 23fps SD. Not great but acceptable.
Next, I fired the rounds loaded with the new, unfired brass. At the first shot, I saw something was up. It chrony'd at 4195 fps, a full 245 fps faster! Knowing my Shooting Chrony occasionally got squirrely, I took note, checked the case for pressure signs (none seen) and continued shooting. Every subsequent shot came in as fast or faster, averaging at 4215 fps, for an overall increase of 335 fps!!!
This was also reflected downrange, as the group had opened significantly, and the POI had shifted 1/2 inch.
Summary:
While I recognize that different case manufacture is cause to redevelop a load, even when manufacturer is the only thing that changes, I did not expect the magnitude of the change I witnessed today when the brass was from the same manufacturer and lot #. I understood that new brass expands when fire formed in a given chamber (in this case, a Remington), but for the virgin brass to have so much less case volume is astonishing.
I acknowledge that with the Grendel, case volume is significantly less than the 22-250, and the usable bullet weights are quite far apart (~50 - 100 grains). Consequently, the effects on a Grendel's MV would likely be less noticeable. That being said, I suspect that any load developed using fire formed brass that is pushing pressures close to the maximum could likely go beyond safe limits, if new cases were introduced without first fire forming them at lower charge weights.
What say the Horde?
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