coloradokevin
Member
- Joined
- Mar 22, 2008
- Messages
- 3,285
I've been handloading for a while, but I've always done so without the aid of a chronograph (never owned one, but always worked my loads up carefully). I recently had the opportunity to put some of my 8mm Mauser loads over a chronograph while shooting at a local range (thanks to another THR member who had such a tool).
Anyway, I was using published Sierra data, working up to loads that weren't quite to the MAX published data. The loads in question were shot from a Yugoslavian M48 Mauser with a 24" barrel, using 175gr Spitzer Softpoint bullets over H-380 powder. My velocities were very uniform (at least in my opinion), but they certainly exceeded the speeds that I expected to see based on the published data. This raised an eyebrow for me, since I believe there is certainly some correlation between velocity and pressure.
Here's the data that gave me pause:
The Sierra load data states that the starting range for this powder is 44.6 grains, and max loads are 53.4 grains. At max loads the published velocity is 2600 fps.
My chronographed loads were as follows:
52.3 grains of H-380: 2,687 fps average (18fps maximum spread in velocity)
52.5 grains of H-380: 2,712 fps average (13fps max velocity spread, with 3 rounds falling within 2fps of each other)
52.7 grains of H-380 (my Max load): 2,742 fps average (46 fps max velocity spread)
So, my question really comes down to asking why my maximum loads were exceeding published velocities by 142 fps, especially considering that I was loading my ammo at least 0.7-1.2 grains below the published maximum charge weight?
Could this be caused by my choice in brass or primers? Seating depth? Something else entirely? If I'm not getting any pressure signs is it safe to use these loads despite the higher velocity?
NOTE: My seating depth was set to 3.150", though the published data seats to 3.100". In my rifle that seating depth does not put the bullet into the lands. Also, I didn't notice any high pressure signs (at least that I could recognize).
Anyway, I was using published Sierra data, working up to loads that weren't quite to the MAX published data. The loads in question were shot from a Yugoslavian M48 Mauser with a 24" barrel, using 175gr Spitzer Softpoint bullets over H-380 powder. My velocities were very uniform (at least in my opinion), but they certainly exceeded the speeds that I expected to see based on the published data. This raised an eyebrow for me, since I believe there is certainly some correlation between velocity and pressure.
Here's the data that gave me pause:
The Sierra load data states that the starting range for this powder is 44.6 grains, and max loads are 53.4 grains. At max loads the published velocity is 2600 fps.
My chronographed loads were as follows:
52.3 grains of H-380: 2,687 fps average (18fps maximum spread in velocity)
52.5 grains of H-380: 2,712 fps average (13fps max velocity spread, with 3 rounds falling within 2fps of each other)
52.7 grains of H-380 (my Max load): 2,742 fps average (46 fps max velocity spread)
So, my question really comes down to asking why my maximum loads were exceeding published velocities by 142 fps, especially considering that I was loading my ammo at least 0.7-1.2 grains below the published maximum charge weight?
Could this be caused by my choice in brass or primers? Seating depth? Something else entirely? If I'm not getting any pressure signs is it safe to use these loads despite the higher velocity?
NOTE: My seating depth was set to 3.150", though the published data seats to 3.100". In my rifle that seating depth does not put the bullet into the lands. Also, I didn't notice any high pressure signs (at least that I could recognize).
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