Pros/Cons of 30 vs 40 degree shoulder?

[sable tireur]

(shoulder hunch)

I don't recognize this term?

Why you would believe some of these statements by Hornady is crazy. It is not beneath them to create some form of BS in order to push their products above other manufacturers. Hornady's cases are soft period. Automated manufacturing with steps which involve pushing the shoulders back does not respond well using soft brass. If they used tougher, slightly harder brass they wouldn't have the problems they suggest. It's much more complicated than this but this is an effort to be short winded...

 

[Mikecr]

Yeah, if only the folks at Hornady would learn basic reloading before making stupid statements..

I agree with 40deg advantages people have identified, and add another:
There are burning efficiencies in holding the powder back (nearest to or in the chamber) with firing. This, in contrast to variably burning powder further down the bore and some at the muzzle. A high shoulder angle tends to hold the powder back, where a shallow shoulder funnels powder right down the bore, as a slug (also adding to bullet mass).

With my next reamer, I'm going to experiment with 60deg shoulders, in fitted chamber, with hopes that I will never have to size the brass. Ever.
Probably a 6.5x47 Imp with BAT action.

 

[DUCKMAN11]

According to Hornady the case is weaker with a 40 degree shoulder and more susceptible to case crush/set back (shoulder hunch) when sizing and loading in tight necks.

I think this is because hornady markets a lot of 30° cases and very very few 40° cases. If you are crushing brass in any case you are doing something wrong.

 

[HuntnPack]

What are the advantages/disadvantages of a 30 vs 40 degree shoulder in a round, if all else is equal?

I've read there is a slight accuracy advantage in a 30 degree shoulder. Any truth to this?

I've also read somehing about less throat erosion and longer barrel life in a 30 degree shoulder...but the proof on this was vague.

Other items I am fairly sure of:
30 degree should feed better (but this matters little in a bolt gun).
40 degree has better case life due to less expansion.

Anything else?

30* vs 40*

In regards to just shoulder angle difference only, no other physical case difference.
For me the advantage goes
to the standard case angle, be it 30* or 40*.

If you have to fire form the case to achieve the shoulder angle then I view that as a slight disadvantage.

In my experience the claimed case length growth is not a huge difference
between these two case angles. & not
worth the effort to alter for that alone.

Also in my experience the process to achieve improved fully fire formed sharpened 40* shoulder angles comes at a cost of
1-2 brass prep, loading, shooting sessions. As well as some increased
Cost in non standard reamers, dies etc.

As far as 30* vs 40*angle only & the effects on burn characteristics, throat erosion, or accuracy benefits, I believe there are too many variables that may have effects outside of just the slight shoulder angle difference & I'm personally not sure there are measurable differences between the two angles to provide benefits to justify changing from 30* to 40*.

Others may view things differently or find benefit in the effort to improve a cartridge case shoulder angle.

Having ran several Improved cartridges & design of my own, it has been an enjoyable learning experience, but the small gains if any were minimal in regards to actual field use and ultimately not worth the effort.

Going forward I've determined my cartridge selection will be of standard 30*, 35*, 40*
Shoulder angle offerings not requiring "improvement" or custom dies.

My time at the bench is better served focused on
Gains to be made with quality reloading equipment. Improved powders, & bullets, & use in quality barrels with correct twist rates & improved barrel materials.

YMMV.

 

[trubkir17]

With my next reamer, I'm going to experiment with 60deg shoulders, in fitted chamber, with hopes that I will never have to size the brass. Ever.
Probably a 6.5x47 Imp with BAT action.

Do you forecast any feeding problems with that shoulder angle or will this be a single shot BR type setup?

 

[Mike Matteson]

Interesting!

 

[Mike Matteson]

30* vs 40*

In regards to just shoulder angle difference only, no other physical case difference. For me the advantage goes
to the standard case angle, be it 30* or 40*.

If you have to fire form the case to achieve the shoulder angle then I view that as a slight disadvantage.

In my experience the claimed case length growth is not a huge difference
between these two case angles. & not
worth the effort to alter for that alone.

Also in my experience the process to achieve improved fully fire formed sharpened 40* shoulder angles comes at a cost of
1-2 brass prep, loading, shooting sessions. As well as some increased
Cost in non standard reamers, dies etc.

As far as 30* vs 40*angle only & the effects on burn characteristics, throat erosion, or accuracy benefits, I believe there are too many variables that may have effects outside of just the slight shoulder angle difference & I'm personally not sure there are measurable differences between the two angles to provide benefits to justify changing from 30* to 40*.

Others may view things differently or find benefit in the effort to improve a cartridge case shoulder angle.

Having ran several Improved cartridges & design of my own, it has been an enjoyable learning experience.
Going forward I've determined my cartridge selection will be of standard
Shoulder angle offerings not requiring improvement or custom dies.

YMMV.

Now days the bushing die has move everything on. No longer have to have a special die made in most cases. In fact I wouldn't get a no-bushing sizing die again. You just change out bushing from on caliber to another with AI shoulders. Depending on what you are sizing too. I use a 280AI FL Redding sizing die to 6mm. The de-primer rod assembly has to be changed out, because the rod is to large to fit in 6mm neck. A 6mm rod won't thread into 280AI die rod assembly. It's smaller. I use my 25/06 bushing die rod assembly and threaded into the 280AI die. That works! In stepping down to 6mm, I had to use 4 different bushing to achieve the final sizes. the one thing I did get was Peterson 280AI case to start with, so that made it easier from the start. From here I looking at doing two things. Having a 25/280AI chamber rifle built. and having another action set up with shorten barrels to do my fire forming. I already have a 6mm/280AI reamer, and now going to get 25/280AI reamer built. If I was just going to use for a standard (or to me) 25/06, 270, 30/06 case I would get just whatever in those sizes cases to fire form. Being the 280AI case is about .1" to the shoulder longer, I was a little afraid that it would be to much to stretch those case into 280AI length to the shoulder. Maybe somebody can tell me if a 270, 30/06 will work for 280AI cases length to the shoulder. I am not totally sure, and don't have the knowledge if they can be substituted or not.

 

[Hard rock]

Now days the bushing die has move everything on. No longer have to have a special die made in most cases. In fact I wouldn't get a no-bushing sizing die again. You just change out bushing from on caliber to another with AI shoulders. Depending on what you are sizing too. I use a 280AI FL Redding sizing die to 6mm. The de-primer rod assembly has to be changed out, because the rod is to large to fit in 6mm neck. A 6mm rod won't thread into 280AI die rod assembly. It's smaller. I use my 25/06 bushing die rod assembly and threaded into the 280AI die. That works! In stepping down to 6mm, I had to use 4 different bushing to achieve the final sizes. the one thing I did get was Peterson 280AI case to start with, so that made it easier from the start. From here I looking at doing two things. Having a 25/280AI chamber rifle built. and having another action set up with shorten barrels to do my fire forming. I already have a 6mm/280AI reamer, and now going to get 25/280AI reamer built. If I was just going to use for a standard (or to me) 25/06, 270, 30/06 case I would get just whatever in those sizes cases to fire form. Being the 280AI case is about .1" to the shoulder longer, I was a little afraid that it would be to much to stretch those case into 280AI length to the shoulder. Maybe somebody can tell me if a 270, 30/06 will work for 280AI cases length to the shoulder. I am not totally sure, and don't have the knowledge if they can be substituted or not.

I'm not sure , but my reloading experience says yes. Of course it will be fire forming on that first shot. I would think a jam on the bullet would be necessary. Try a mild load , like I said I'm not sure but I bet it will work.

 

[Hard rock]

I'm not sure , but my reloading experience says yes. Of course it will be fire forming on that first shot. I would think a jam on the bullet would be necessary. Try a mild load , like I said I'm not sure but I bet it will work.

I would like too hear more about this myself

 

[dennisinaz]

Having made thousands of wildcat cases, i find that i get many times the failure rate of 30⁰ when moving to 40⁰. 30 is like a magic number. I wouldn't do another improved unless it was 30⁰ or close to it without a really good reason (i have several Ackley improved reamers and would consider those because i have the reamer, dies etc.)
My most recent venture into weird is the 6SLR. It is 30⁰ i think. We can make fun of that Hornady guy in thy Podcast but i don't think he was fibbing.

I have a 260 AI that i really like but forming brass is not fun. Making 6SLR brass is easy

 

[Mikecr]

Do you forecast any feeding problems with that shoulder angle or will this be a single shot BR type setup?

Any of my guns (factory or custom) are single shot or converted to single shot, with safety and ejector delete.
If the case was a short 6br variant at 60deg, I would likely have a rattle with feeding. I believe a 6.5x47 will be as short as I can go with such a high shoulder angle. The tray on my BAT is exactly centered for .473 case head cartridges.

Before I built a WSSM variant, I watched people struggle with feeding of that animal. I went with 35deg shoulders there.
But Bruce Thom at BAT built me an action FOR the WSSM and it feeds like butter on a biscuit. So if a 6.5x47 works in 60deg, I'll change my WSSM to that as well.
The WSSM is a short-fat cartridge that well demonstrates efficiency -as claimed. It's design dimension ratios hold the powder back, and I have to turn efficiency way up in QL (weighting factor) to calibrate with my load.
There is something to it, as my 26WSSM Imp can smoke a 6.5x284 (10gr higher H20 cap) with same bullet and barrel length.
My accurate barrel life is also ~1850rnds, where a 6.5x284 is ~1200.

Even if satisfied with a standard cartridge, for reloading, case improvements including lower body taper and higher shoulder angles, can greatly increase case life. This, by reducing stretch and sizing requirements, leading to less brass movement/trimming. With capacity gain you could, if you wanted to, back off a bit on peak pressure to gain even more in brass and barrel life.
And as far as fire forming to fit the chamber, we all do that anyway. A case is fully formed by your chamber (your best die).
It helps to do a deep body dip anneal before 1st firing.

 

[elkaholic]

Any of my guns (factory or custom) are single shot or converted to single shot, with safety and ejector delete.
If the case was a short 6br variant at 60deg, I would likely have a rattle with feeding. I believe a 6.5x47 will be as short as I can go with such a high shoulder angle. The tray on my BAT is exactly centered for .473 case head cartridges.

Before I built a WSSM variant, I watched people struggle with feeding of that animal. I went with 35deg shoulders there.
But Bruce Thom at BAT built me an action FOR the WSSM and it feeds like butter on a biscuit. So if a 6.5x47 works in 60deg, I'll change my WSSM to that as well.
The WSSM is a short-fat cartridge that well demonstrates efficiency -as claimed. It's design dimension ratios hold the powder back, and I have to turn efficiency way up in QL (weighting factor) to calibrate with my load.
There is something to it, as my 26WSSM Imp can smoke a 6.5x284 (10gr higher H20 cap) with same bullet and barrel length.
My accurate barrel life is also ~1850rnds, where a 6.5x284 is ~1200.

Even if satisfied with a standard cartridge, for reloading, case improvements including lower body taper and higher shoulder angles, can greatly increase case life. This, by reducing stretch and sizing requirements, leading to less brass movement/trimming. With capacity gain you could, if you wanted to, back off a bit on peak pressure to gain even more in brass and barrel life.
And as far as fire forming to fit the chamber, we all do that anyway. A case is fully formed by your chamber (your best die).
It helps to do a deep body dip anneal before 1st firing.

Ditto!

 

[Calvin45]

Having made thousands of wildcat cases, i find that i get many times the failure rate of 30⁰ when moving to 40⁰. 30 is like a magic number. I wouldn't do another improved unless it was 30⁰ or close to it without a really good reason (i have several Ackley improved reamers and would consider those because i have the reamer, dies etc.)
My most recent venture into weird is the 6SLR. It is 30⁰ i think. We can make fun of that Hornady guy in thy Podcast but i don't think he was fibbing.

I have a 260 AI that i really like but forming brass is not fun. Making 6SLR brass is easy

Always appreciate when people speak from experience. Good to know. I wanna do a wildcat of some kind one day.

 

[SSgt G Cody]

I see no reason to ever go below 30 degrees in a rifle case again. I have 3 bolt-action rifles with 40 degree shoulders that shoot and cycle great, plus 7 others with 30 degree shoulders. I think the full-auto military rifles are the only guns that still need low angle shoulders for extreme reliability.