Armory Sponsor
Posted: 3/8/2011 4:37:58 PM EDT
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We all know that brass has different capacities. Even brass from the same manufacturer may vary from year to year or even lot to lot. My question is, would it not be possible to just keep track of your brass capacity by head stamp and then adjust your loads accordingly. For example, you've worked up a good load using LC brass but now you want to switch to Winchester commercial brass. Now lets say that the Winchester brass has a 1% larger capacity. Couldn't you just up your load by 1% and call it a day, or does it not translate that way? Anybody done any testing along these lines?
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Quoted:
Answer depends on if you are talking about 223 or 308. For the sake of discussion lets say .308. I haven't measured it yet, but I know there is a difference in capacity between LC brass and Winchester commercial. Winchester having more capacity. Aero...I would measure capacity using a fine ball type powder as opposed to water. Also, lets assume I would be using the same powder in my load as I used to measure capacity. |
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Quoted:
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Answer depends on if you are talking about 223 or 308. For the sake of discussion lets say .308. I haven't measured it yet, but I know there is a difference in capacity between LC brass and Winchester commercial. Winchester having more capacity. Aero...I would measure capacity using a fine ball type powder as opposed to water. Also, lets assume I would be using the same powder in my load as I used to measure capacity. Makes sense to me. I don't sort my brass for regular rifle loads, well below max loads. Do some measuring, chrony a few, and see if the math holds up in real life. I just looked up Hodgdon 4895 for a 165gr bullet. Starting load is 41 grains, so dumping 41.4 in a case that measures 1% larger? I'd do that. Chrony the results and see how it compares to 41 in the smaller case. If you're talking hot loads or want maximum accuracy thats another story. Jumping up that way with a hot load is a particularly bad idea. |
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Quoted:
We all know that brass has different capacities. Even brass from the same manufacturer may vary from year to year or even lot to lot. My question is, would it not be possible to just keep track of your brass capacity by head stamp and then adjust your loads accordingly. For example, you've worked up a good load using LC brass but now you want to switch to Winchester commercial brass. Now lets say that the Winchester brass has a 1% larger capacity. Couldn't you just up your load by 1% and call it a day, or does it not translate that way? Anybody done any testing along these lines? If you are a comfortable amount below max load , I would just load up some rest rounds and give it a try . And go from there . God bless Wyr |
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Quoted:
Quoted:
We all know that brass has different capacities. Even brass from the same manufacturer may vary from year to year or even lot to lot. My question is, would it not be possible to just keep track of your brass capacity by head stamp and then adjust your loads accordingly. For example, you've worked up a good load using LC brass but now you want to switch to Winchester commercial brass. Now lets say that the Winchester brass has a 1% larger capacity. Couldn't you just up your load by 1% and call it a day, or does it not translate that way? Anybody done any testing along these lines? If you are a comfortable amount below max load , I would just load up some rest rounds and give it a try . And go from there . God bless Wyr My question isn't really directed at safety, more in replicating a known load. ie.....velocity and accuracy. I realize that there probably isn't a true linear relationship, but can anyone here say that for sure. We aren't talking about using capacity to go from 308 to 50bmg, just from headstamp to headstamp within the same caliber. |
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I usually see 2.0 grain difference in powder charges to achieve the same velocity going from Lake City to Winchester. I would not automatically assume 2.0 whole grains, but it's usually pretty close. If I'm using 40.5 grains of IMR-4895 in Lake City with 168 SMK's then I'll probably be really close with 42.5 grains in Winchester brass. BTW - I consider both of these maximum loads. Only add 1.0 grain to start.
All Winchester brass is not identical. The lightest I've seen weighs around 155 grains. Most Lake City is closer to 178/180 grains unprimed. Weigh your brass before you start to see how big the difference actually is. If you are close to these figures 2.0 grain difference is close. If the brass weights don't have a 25 grain spread then you won't be able to add 2.0 grains, less will do the trick. It is pefectly safe to load the lighter Winchester brass with any load that was safe in Lake City. You can use that as the starting point for your load work up. |
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There can be slight differences in case weight due to extractor cut dimensions but these are tiny compared to the interior volume when comparing identical brands. Case weight IS a good indicator of case volume which isn't affected by sizing. And because brass is 8 times the density of water, it is more sensitive than using water weight method. |
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