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Thread: Case water volume etc

  1. #1

    Default Case water volume etc

    In the pushing the limits thread case volume was mentioned. If Federal and remington cases hold less water than WW, what does , for instance, 3 gains less volume mean? if not just that and the need for more powder to achieve the same velocity in a WW case? I read that a 7x57 WW case weighs nearly 22 grains less than a federal case. Does this mean that the walls are thinner and thus weaker? I expect it is moot for the cautious amongst us but is the case technically weaker? will it stretch more and should you reload them fewer times?

    On the other hand I have found that federal cases have split necks when reloading without annealing in my M96 mauser, Norma brass does no such thing. I have put it down to more elastic brass in the case of Norma and generous dimensions in the 96. Is federal brass too thick or inelastic. (an incorrect technical term i am sure)

    Cheers

  2. #2
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    Default Works under pressure, Springs back for more....

    Here's my take on brass.

    The difference in capacity of the different brands only matters if you mix cases or switch brands after working up a max or near max load. Safety is the issue of going from W-W headstamp to R-P with your max load. Things could get sticky. Vice versa, going to W-W from R-P would likely only wreck your load recipe at worst case.

    I have found R-P to be good brass and in some rimmed calibers I would prefer it over W-W. Some calibers are single sourced and some have many brands to choose from. Yes the walls of R-P and Fed are thicker than Norma or W-W. Another issue here is what is known as anneal gradient. A case should be harder at the base and walls and softer at the shoulder and neck area to allow for it to expand and contract at the walls and expand and resize at the neck and upper shoulder.

    When a case is fired it expands out against the chamber wall and will then spring back after the pressure drops, this allows easy extraction. The case neck will expand out but will not contract back much at all and will be resized back to correct dimensions. Resizing dies are dimensioned in such a way to allow for this brass behavior, especially at the neck. We over size the neck a couple of thousandsths and it springs back about one. If the case neck is too hard it will spring back more or if too soft won't spring back enough and will have the wrong dimensions to hold the bullet correctly. This leaves a perfect looking piece of brass that is worthless unless we have custom made dies for it. Not an option. Of course the reverse problem comes with some brass. Really good brass is not only of the correct dimension but of the correct anneal or temper to behave under the pressure of its cartridge design.

    Another big job of brass is to use itself as a emergency gasket at the back of the chamber when we over pressurize the case when loading. The thick base of the case, the web, is the best safety valve we have to keep hot gas out of our face when things go wrong.

    If the anneal (temper) is wrong at the base or the neck or anywhere in between the brass is not the best it could be. I have said that I prefer R-P brass for some calibers. Rimmed calibers generally run at less pressure than modern beltless or belted mags. Remington brass with it's thicker walls and softer anneal, they seem to be pretty consistantly so from caliber to caliber, rim or not, works better that W-W. Federal rifle brass has been so inconsistant lot to lot and often is annealled up side down. Hard on top and soft on the bottom. I have abandoned it.

    The term soft or hard refers to the temper of the brass and is the result of annealing (making softer) or not annealing. Brass can be too soft or too hard (brittle). Brass has to take a certain pressure and spring back, such as the side walls of a case. If it doesn't spring back, it will be hard to extract. If it is too soft at the side walls it may not spring back under normal pressure. If it is of the correct anneal it will not spring back under excess pressure. The brass has been over worked and become fixed in place. All this applies all along the case, top to bottom. Each has a certain behavior expected of it when it is fired. It is a tall order for brass to be able to do this after many firings.

    Brass is very soft when it is formed but is work hardened and must be annealed correctly by the maker to be on its best behavior for us. Rarely is brass so consistantly, correctly annealed top to bottom to make its behavior so predictable as to rely on it to judge the pressure of the load. We all still do this to some degree and that's why we have our favorite brass brand. I like W-W because it seems to behave the way I expect, most of the time. Norma is very similar to W-W in dimensions, weight and anneal gradient. Lapua is top notch but like Norma only available for some few calibers.

    Brass that is perfect when new can become work hradened by firing and sizing, firing and sizing operations and can be saved or have it's life extended by proper annealing, it can also be ruined by improper annealing. Annealing can be done in the privacy of your own garage or back yard. All it takes is a torch (Ox-Acet., butane, etc) a 650 degree F crayon and a bucket of water. Well maybe a few more things than that for best resluts, but it isn't rocket science. Basically it consist of heating the part of the case that we want to be softer to a temperature of 660 F then dropping into a bucket of cold water. Yes that really softens it. The trick is don't heat above 660 F and don't heat the body more than necessary.

    I paint the case in a circular mark around where I want the anneal to stop with 650 F crayon, when it turns color (indicating it is 650 F) remove heat and dunk in cold water. The neck would get the 660 F stripe and the stop point on the shoulder would get the 650 F stripe. I'm having trouble finding the 660 F crayon here in this town so I'll just guess and use the stop stripe at the shoulder. Heating to a higher temp then dunking softens the brass more, heat to lower temp softens it less. The brass actually glows red but you can't see this or the stripe very well in bright sun light. You can also melt the brass and it will drip on your shoes. I think it melts at 670 F.
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  3. #3

    Default

    Thanks

    Without really knowing why I have also found federal to be less consistant than RP and Norma. I have a pile in 7mm and 6.5mm mauser from a sporting goods closeout sale of federal classic ammo that was cheaper than brass. but when they have come to the end of their lifespan I will stick with RP

    I can only get .300 savage in WW and I expect the case capacity will explain my lower than expected velocity. So I will load to the chrono.

    Would I get one of those 650 f crayons from a welding shop?

    Cheers

  4. #4

    Default

    Quote Originally Posted by 35gibber View Post
    Thanks

    Without really knowing why I have also found federal to be less consistant than RP and Norma. I have a pile in 7mm and 6.5mm mauser from a sporting goods closeout sale of federal classic ammo that was cheaper than brass. but when they have come to the end of their lifespan I will stick with RP

    I can only get .300 savage in WW and I expect the case capacity will explain my lower than expected velocity. So I will load to the chrono.

    Would I get one of those 650 f crayons from a welding shop?

    Cheers
    I just checked with a welding shop here, and though he stocks pens he was out of the 650's. Said he would get me some, but he's a little sloppy about ordering, so I'll probably have to nudge him once or twice more. Didn't seem at all surprised by my request, more like he was surprised he was out, so I'm betting a good welding shop that's a little better run could track you down some pretty quick, if he didn't already have them on hand.

    I'm kinda surprised you couldn't get any 300 Savage RP cases. No wait. I should say that's what I'm using, but it's been a while since I bought.

    I've never had much trouble with Fed cases, with the exception of one lot of 7x57 cases. Fortunately I only loaded one box when they first arrived, because I got 4 neck splits on first firing with moderate loads. I sat down and annealed the other 180 cases before loading and haven't had a problem since. I'm betting they're on their fifth or so loading now and ready for annealing again, but I haven't had another neck split in all that firing.

  5. #5
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    Default

    I hope everyone knows that the crayons are not the only game in town. I never used the crayons, cause McMaster-Carr wants to much money. You can go or call your locale welding supply house in Anchorage, there's two.

    I use the liquid in the bottle with the nail polish type brush. I got it from Hornady when they sold the annealing kits. I think you can get the right temp bottles from Brownells under the name of Tempilaq(?) I think a few bottles would last a life time if you use them to set the speed for your annealing machine (if you use one) I like the idea of a flame bar that you get from these machines, just like the factories use to prevent to deep annealing.
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