- Date: 30 August 2025
- Range: West End Gun Club (Meyers Canyon, CA)
I made an early Saturday morning range trip to work through 20 rounds I loaded for the 7PRC in an attempt to figure out why the SD (standard deviation) I have been getting is so high (15 to 20+). Even with a small sample size of 5 rounds, I would expect under 10 SD.
I decided to try and figure out the high SD issue in two ways:
- Testing with 1x Fired / Fireformed ADG brass
- Testing with CCI BR2 Large Rifle Benchrest primers (not magnum)
With the first item, my thought process was that perhaps the factory brass even with full-length sizing and running through bushing and then a mandrel wasn’t getting the brass consistent from case to case, and that a fire-formed case and then re-processed all the same (FL and mandrel) would result in better SD.
With the second item, I did some research and came across web forum posts and discussions about how people used standard Large Rifle primers (non-magnum) in magnum cartridges to good effect with SD.
Components:
- ADG 7mm PRC Brass
- Hodgdon H1000
- Berger Bullets 7mm 175gr Elite Hunter
I brought out my SPR gas-gun rig to shoot while I waited for the PRC to cool off between strings. This SPR was changed since it’s last outing and now sports a Magpul PRS Gen 3 stock and an Ultradyne Apollo Max muzzle brake.
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