Redmt
Well-known member
What is the difference or what effect does shoulder angle on reloading cartridges have? I've been reloading forever and always note this cartridge or another has different and specific shoulder angle and am wondering why?
Shoulder angle
- Thread starter Redmt
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p_ham
Well-known member
They affect feeding, case capacity, case stretch...
The more shallow the shoulder angle the smoother the cartridge will feed (generally).
A lot of factory cartridges adopted the 20⁰-30⁰ shoulders because you get a good blend of feeding reliability, case capacity, and the biggest driver, ease of manufacture.
There have been arguments as long as bottleneck cartridges have been around as to what angle lends itself to accuracy the best.
The more shallow the shoulder angle the smoother the cartridge will feed (generally).
A lot of factory cartridges adopted the 20⁰-30⁰ shoulders because you get a good blend of feeding reliability, case capacity, and the biggest driver, ease of manufacture.
There have been arguments as long as bottleneck cartridges have been around as to what angle lends itself to accuracy the best.
VikingsGuy
Well-known member
Sharper angle tends to increase case capacity and decrease case lengthening. Hence the beauty of AI family cartridges (those also have decreased case body taper to add case volume).
Redmt
Well-known member
The actual base of the question was re: the 6.5-284. There is a question to Norma vs. Western. RCBS said their die accomodates either because of the 35* shoulder angle. An earlier reloading book cautions against mixing up the Norma vs. Western. I'm just curious how there would be an issue when RCBS says their interchangeable.
44hunter45
Well-known member
If you want a deep dive into shoulder angles and case taper, get both volumes of P.O Ackley's book "Handbook for Shooters and Reloaders." Every 264/6.5mm guy should read his chapter on "Bore Capacity". My copy has a post-it note marking page 164.
Here's my TLDR answer on mixing brands. You have to understand that I am sometimes more retentive about the PROCESS than the RESULTS.
Regarding Norma vs Western brass - They may have different case capacity for the FIRST firing, therefore you wouldn't want to mix them unfired for a max load. Safety says any time you change a variable in your recipe, you re-run your pressure tests.
You really can't compare until the brass has the exact same external dimensions. If you have the time and components on hand, load them with a starting charge from your manual and run them through your rifle at the range. I have a corner of my powder storage for those powders that have not impressed me. These are my fire forming powders. Do not use a starting charge that doesn't fill a good portion of the case (65-70%). Flashover is a real thing. There are fillers you can use if you want to fire-form with lower charges. I don't . I wouldn't compress the charge either.
In practice once they have been fired in your rifle, neck only sized, and trimmed - they will have the shoulder angle of your chamber. Full length sizing in the RCBS die is going to bump the shoulder to their 35° depending on how you have it set up. I would want the die to do as little as possible to the shoulder of my fired brass.
Various brands of brass have their own metallurgy, web and case wall thickness, etc. BUT - If you have fired the cases in your rifle chamber, re-sized them in the same die, and trimmed them to the same length it is very likely that if the cases weight the same, they have essentially the same internal capacity.
Here's my TLDR answer on mixing brands. You have to understand that I am sometimes more retentive about the PROCESS than the RESULTS.
Regarding Norma vs Western brass - They may have different case capacity for the FIRST firing, therefore you wouldn't want to mix them unfired for a max load. Safety says any time you change a variable in your recipe, you re-run your pressure tests.
You really can't compare until the brass has the exact same external dimensions. If you have the time and components on hand, load them with a starting charge from your manual and run them through your rifle at the range. I have a corner of my powder storage for those powders that have not impressed me. These are my fire forming powders. Do not use a starting charge that doesn't fill a good portion of the case (65-70%). Flashover is a real thing. There are fillers you can use if you want to fire-form with lower charges. I don't . I wouldn't compress the charge either.
In practice once they have been fired in your rifle, neck only sized, and trimmed - they will have the shoulder angle of your chamber. Full length sizing in the RCBS die is going to bump the shoulder to their 35° depending on how you have it set up. I would want the die to do as little as possible to the shoulder of my fired brass.
Various brands of brass have their own metallurgy, web and case wall thickness, etc. BUT - If you have fired the cases in your rifle chamber, re-sized them in the same die, and trimmed them to the same length it is very likely that if the cases weight the same, they have essentially the same internal capacity.
