Looking for credible articles/papers/research references for the below

Justice1327 · Thursday at 9:48 AM

1. How does a sharper shoulder angle on a rifle case help with combustion?

2. How might the surface of the chamber affect ballistic performance?

Currently reading Ammunition Demystified for the second time.

Thank you

Mikecr · Thursday at 10:06 AM

I won't do a bunch of research for you, but higher shoulder angles increase powder burn in the chamber -instead of further down a bore. It holds the powder back.
A grippy chamber helps with consistent brass stretch, which affects volume of containment and bolt thrust. It holds brass forward.

OG10 · Thursday at 10:15 AM

Here let me google that for you…

Justice1327 · Thursday at 10:37 AM

Mikecr said:
I won't do a bunch of research for you, but higher shoulder angles increase powder burn in the chamber -instead of further down a bore. It holds the powder back.
A grippy chamber helps with consistent brass stretch, which affects volume of containment and bolt thrust. It holds brass forward.

I believe I know these things too, but looking for more "high level" ballistic papers/ lab results/ that have references to their criteria. for example, expand upon how a chamber impacts internal and possible external ballistics.

Zen Archery · Thursday at 6:21 PM

Justice1327 said:
1. How does a sharper shoulder angle on a rifle case help with combustion?

2. How might the surface of the chamber affect ballistic performance?

Currently reading Ammunition Demystified for the second time.

Thank you

Bryan Litz, John Harrison, and RG Hagel will keep you busy for a while.

wilehunting · Thursday at 7:52 PM

P. O. Ackley could be a good reference. He liked a 40 degree shoulder, his improved cartridges have more capacity over standard base cartridge, more power burned in case, more efficient, less extreme velocity spread, less throat erosion, less bolt thrust, less case stretch.

Koda_ · Thursday at 8:21 PM

Justice1327 said:
1. How does a sharper shoulder angle on a rifle case help with combustion?

2. How might the surface of the chamber affect ballistic performance?

Currently reading Ammunition Demystified for the second time.

Thank you

1. helps improve keeping the cartridge centered in the bore over shallower shoulders.
2. smoother throat less pressure. (Im not certain about the chamber surface itself but this is as close as I know of...)

1: https://www.outdoorlife.com/guns/modern-cartridge-design/
2:

Justice1327 · Friday at 4:59 AM

Zen Archery said:
Bryan Litz, John Harrison, and RG Hagel will keep you busy for a while.

John harrison is new to me… I will look into that thank you. Brian Litz doesn't really talk that much about chamber and it's interaction with the Brass. I have all of his books.

Justice1327 · Friday at 7:34 AM

Koda_ said:
1. helps improve keeping the cartridge centered in the bore over shallower shoulders.
2. smoother throat less pressure. (Im not certain about the chamber surface itself but this is as close as I know of...)

1: https://www.outdoorlife.com/guns/modern-cartridge-design/
2:

1. Yes, agreed and this is part of what I am looking into...to find the science behind it. interesting to see how some modern cartridges use a smaller freebore diameter than traditional comparable cartridges. For example 7mm Mauser is .2907 and a 7 PRC is .2846. Also the lead angle for similar cartridges has changed over the years. I would assume because bullet design has changed to. But I am no expert and that is why I am trying to find answers.
2. I read in Siewart's book about how too much, or any, lubrication is left on a cartridge case and is fired that it can double the pressure that is thrust back on the bolt face. I am going to have my barrel burning cartridges nitrided and was concerned if it made the chamber "slicker" that it might increase the bolt thrust beyond what is acceptable to the manufacturer.

MagnumManiac · Friday at 7:52 AM

I will tell you this for 100% certainty, shiny, polished chambers are BAD, sanded chambers are GOOD.
Rough chambers full of chatter, are BAD, polished, but sanded finished with emery cloth, are GOOD.

Surface finish is all important for HOW the brass reacts to the chamber walls, not necessarily the chamber design.
Throats need to be TIGHT, .0005" over bullet diameter is what I strive for…

Cheers.

Justice1327 · Friday at 8:00 AM

wilehunting said:
P. O. Ackley could be a good reference. He liked a 40 degree shoulder, his improved cartridges have more capacity over standard base cartridge, more power burned in case, more efficient, less extreme velocity spread, less throat erosion, less bolt thrust, less case stretch.

Yes, I like and prefer AI cases myself. I am just looking for the "science data" behind all of the beliefs that it does reduce SD, define more efficient, proof of less throat erosion etc...

FEENIX · Friday at 8:30 AM

Justice1327 said:
Yes, I like and prefer AI cases myself. I am just looking for the "science data" behind all of the beliefs that it does reduce SD, define more efficient, proof of less throat erosion etc...

What do you consider science data? Actual lab scientific data, or a reputable author? Ackley, Zeglin, Litz, etc., are what I consider reputable authors, not Spoomer.

Justice1327 · Friday at 9:15 AM

FEENIX said:
What do you consider science data? Actual lab scientific data, or a reputable author? Ackley, Zeglin, Litz, etc., are what I consider reputable authors, not Spoomer.

Yes, Zeglin, Siewart, Litz all provide their data. Army, Navy research papers are all good.
Spoomer is entertaining, but not credible for what I need.
Ackley was a designer/hunter and very opinionated...which is fine, just lacks credible data for the areas i am looking into...but he was obviously a leader and had great foresight on cartridge case design.

Justice1327 · Friday at 9:17 AM

MagnumManiac said:
I will tell you this for 100% certainty, shiny, polished chambers are BAD, sanded chambers are GOOD.
Rough chambers full of chatter, are BAD, polished, but sanded finished with emery cloth, are GOOD.

Surface finish is all important for HOW the brass reacts to the chamber walls, not necessarily the chamber design.
Throats need to be TIGHT, .0005" over bullet diameter is what I strive for…

Cheers.

Yes, agree. that is why I am looking into a nitrided chamber and what it may or may not do. Obviously I am not the first, just looking for information on it and how chamber design/shape has changed and any proof that a particular change in design from past is quantifiably better.

Looking for credible articles/papers/research references for the below

Justice1327

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Mikecr

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OG10

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Justice1327

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