Mixed headstamps, same weight

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pacobillie

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We all know that it is supposedly not advisable to mix rifle brass of different headstamps, because of discrepancies between manufacturing processes/ specifications.

However, I recently noticed that several brands (Federal, WW Super, Imperial, Remington-Peters) of 7mm Rem Mag cases have nearly identical weights, whereas Hornady cases have weights that are all over the place.

Would I not be better using cases of similar weight, even if the headstamps are different, as opposed to matching headstamps (irrespective of weight).

Of course, ideally, headstamps and weights should match.
 
And probably need some statistic math abilities to find that answer - recently did that for nny headstamp versus PPU headstamp in 9.3x62. Are they the same or different?? I weighed 5 of each with a fired primer - single heaviest (was not the longest) was nny. Single lightest (was not the shortest) was PPU. Full length sized all 10 - then filled each to brim with water and re-weighed each. There was greater variation among the 5 of each brand, then there was between the average of nny versus the average of PPU. I still do not know if they are the "same" or "different" - can not find my old math books about statistical analysis to determine what is statistically significant for a sample size of 5 out of a population of the 150 of each that I have on hand.
 
Different brands of brass will have slightly different alloys of brass. I would think that could affect how tight the bullets are held in the neck and could have an affect on accuracy. Also the number of times fired will affect the hardness of the necks. Annealing softens the necks so they are all the same. So I would like to see same brand close to same weight and same number of firings
 
it mostly depends on what you do.

plinking at at short distance... it makes no difference.

I've noticed that some brands like Federal have multiple factory and they're different depending on where it is made.
 
pacobillie said:
We all know that it is supposedly not advisable to mix rifle brass of different headstamps, because of discrepancies between manufacturing processes/ specifications.

However, I recently noticed that several brands (Federal, WW Super, Imperial, Remington-Peters) of 7mm Rem Mag cases have nearly identical weights, whereas Hornady cases have weights that are all over the place.

Would I not be better using cases of similar weight, even if the headstamps are different, as opposed to matching headstamps (irrespective of weight).

Of course, ideally, headstamps and weights should match.
Click to expand...

Would make me suspicious that all these folks buy their components from the same "jobber" factory in bulk with their own head-stamp impassions.
 
If you consider the ops question, he has already tied the weight of the case to the effect on pressures and he is not wrong.

Forget about the capacity of the brass as the brass it actually not the chamber that determines pressure... it's the rifle chamber. When the cartridge is fired, the case is blown out to the chamber dimension.

Another point is that metals are sold by weight and every metal has a conversion factor that converts its size to its weight. In other words, the weight of the case is a direct representation of how much air space inside the rifle chamber that will be displaced by the presence of that amount of brass.

Attempting to measure case capacity by water is a very crude means of approximating capacity but it is by no means an effective method of sorting brass volumetrically. Even if it was highly predictable, it would only matter on the case after it had been fired in your rifle.

The only wild card might be some other way out of spec factor like a visibly different chamfer size on the rim, or chrome plated brass as that contaminates the base assumptions. Other than that... yes same brass weight equals same volumetric displacement therefore same velocity.
 
For typical hunting accuracy in a 7mm RM I doubt it matters to sort cases. Try it with low end loads, you'll probably be surprised.
 
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