Does changing brass change pressure sensitivity?

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Yedi

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Hi Guys,

I started reloading. I'm doing 300 win and I was working up a load. I had done a test run all the way to book max with no problem in Remington Brass.

I then loaded 20 each of the best 2 loads, plus two fowling shots at book max.

The fowling shots in Remington brass was fine. The first 20 rounds in Remington brass was .7 grains under max and shot fine. The next 20 were .3 grains under max but loaded in once fired Winchester Brass. They weren't so good. Hard extraction. The brass had been full length resized although they weren't fired from my gun originally. Bullet seating was at book spec so.

So any guesses why that happened? Can the brass affect the pressure that much?
 
I think you just proved it.

Edit for another thought: Did the barrel and chamber heat up during the process and possibly influence the results of later shots?
 
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Yedi said:
Well...I was hoping I did something wrong that I could fix without running two recipe's
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I find a recipe includes the brand of brass as part of it. You can often find a couple brands that work with the same other parts of the recipe but one powder/primer/bullet recipe may not work with all brass.

My .300 Win Mag loads are closer to the minimum end of things for best accuracy in my rifle so I can use any brass I like with no effect on extraction (though it does change accuracy). When I was experimenting with near max or max loads I found that Federal brass didn't like being pushed that hard and would be hard to extract and have ejector indentations on the heads (Federal brass is softer than most.)

Different brands of brass have different thicknesses and different internal volumes as a result (since the external dimensions are generally the same.) I find Winchester brass is lighter and has thinner walls than Remington so I would have guessed it would be lower pressure but I guess not in your case.
 
Brass varies from manufacturer to manufacturer. You should not simply keep the same powder charge when changing other components - this goes for primers and bullets of different style/manufacturer.
 
Even brass from the same manufacturer may vary from lot-to-lot.
Internal capacity varies enough to get one into trouble in some cases.
For example, in a Winchester 7x57 case, 54 grains of MRP fills the case to the bottom of the neck
In a Remington 7x57 case, you cannot get 54 grains of MRP in.
Be careful! There are pitfalls out there.
Regards, Eagleye.
 
That is a good reason why it is a good idea to buy 50 or 100 rounds of new brass from the same lot for high performance loads. If you are loading mid-range plinking loads it is no so big an issue but is an issue non the less.
 
The different brass (internal dimensions) may have contributed to a higher pressure which was the cause of the tight bolt or perhaps the material of the cartridge was softer and behaved differently in the chamber causing the apparent higher pressure. IMHO you can't be certain unless you measure the pressure.

If you used the same primers, do they look to be deformed equally (even this you have to consider the shape of the primer pocket, flash hole size, etc, etc ,etc. and is very subjective
 
As stated before you should always stick to one brand of brass, however in your experiment I can tell you from personal experience any load you work up in a 300 WM in R-P brass will be lower pressure and absolutely safe in W-W brass. W-W brass is consistantly 10+ gns lighter in the 300 WM equating to greater internal capacity. I would be looking for another flaw somewhere in your process. Change of bullet weight or shape, change in COAL, W-W brass over length and jamming into leade. You need to prep all your brass the same for first time firing in a rifle. Full length size or fit to chamber if you know how, trim all to book min, clean all primer pockets, use all the same primers, use the same method to charge your cases with the same powder and seat your bullets to the same COAL. Now you are ready to compare differences in brass.
 
c-fbmi said:
As stated before you should always stick to one brand of brass, however in your experiment I can tell you from personal experience any load you work up in a 300 WM in R-P brass will be lower pressure and absolutely safe in W-W brass. W-W brass is consistantly 10+ gns lighter in the 300 WM equating to greater internal capacity. I would be looking for another flaw somewhere in your process. Change of bullet weight or shape, change in COAL, W-W brass over length and jamming into leade. You need to prep all your brass the same for first time firing in a rifle. Full length size or fit to chamber if you know how, trim all to book min, clean all primer pockets, use all the same primers, use the same method to charge your cases with the same powder and seat your bullets to the same COAL. Now you are ready to compare differences in brass.
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My 338 Win brass is 4 grains lighter in Remington than it is in Winchester. I worked up my loads in Win then switched to Remington brass with no problems. Best to weigh your brass when switching brands.

G
 
A fouling shot is the first shot through a clean barrel to "foul" it.
Usually done to make sure that subsequent shots are fired on a level playing field.
Often, the first shot from a clean barrel will be out of the group, sometimes quite a bit.
Regards, Eagleye.
 
g-manz35 said:
My 338 Win brass is 4 grains lighter in Remington than it is in Winchester. I worked up my loads in Win then switched to Remington brass with no problems. Best to weigh your brass when switching brands.

G
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WOW, that's a first. Almost every case I've weighed regardless of caliber W-W has been significantly lighter than R-P, Fed, Norma, Lapua or Horn.
The only case I've found lighter than W-W consistantly is Nosler. I'll have to check my 338 brass as I have lots of both W-W and R-P.
 
c-fbmi said:
WOW, that's a first. Almost every case I've weighed regardless of caliber W-W has been significantly lighter than R-P, Fed, Norma, Lapua or Horn.
The only case I've found lighter than W-W consistantly is Nosler. I'll have to check my 338 brass as I have lots of both W-W and R-P.
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The (338 Win Mag) Win cases are the silver ones from their premium loads not the reg brass. My 270 brass in Win seem to be the lighter than everything else I have used. That's why I said best to weigh the brass you have and not assume.

And yes this is covered in just about any reloading manual.

G
 
On sub max loads, I've used mixed brass for general range plinking and seen little detriment. But for hunting or true target shooting, its one brass and a load built and tested on that brass, powder, bullet primer, trim length, crimp, seating depth.
 
different internal dimensions and seating depth both change pressures no question. most precision reloaders use neck-sizing dies only to keep things as consistent as possible.
 
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