Already there. Polymer cases, steel caseheads.
30%-40% lighter than brass cased, a game-changer for mil applications.
277 Fury Pressure and modern components - WAS: Impact of shoulder vs nut on strength/max pressure capacity
- Thread starter nkyshooter
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30%-40% lighter than brass cased, a game-changer for mil applications.
cohunt
Well-Known Member
But-- are there any bolt action manufactures stepping up and saying their actions are in fact safe to use with the 277 furry 80k cartridge?
I havent seen any yet, which begs to differ if they are confident their actions/bolts would hold up to the 80k pressures over the lifetime of the firearm.
As I said, there have been prior tests on action strength but the only manufacturer that I know of who has done proof load and longevity testing with 80k cartridges is sig
Other thing to consider down the road is bolt thrust calculations-if the 80k becomes something that advances, the larger the bolt face- the more the bolt thrust due to the higher pressures.....right now I only know of the 277 furry that runs 80k but if they bring out a short mag or lap sized cartridge the bolt to action lock up/strength may become an issue
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nkyshooter
Well-Known Member
Source?
cohunt
Well-Known Member
I wonder about longevity of bolt lug/action interface/contact area
I know that in the past there were some issues with titanium bolt/actions where some people had recorded increasing head space issues due to lug/action lock up area "stretching" on cartridges with larger bolt faces ( higher bolt thrust numbers)
I know that in the past there were some issues with titanium bolt/actions where some people had recorded increasing head space issues due to lug/action lock up area "stretching" on cartridges with larger bolt faces ( higher bolt thrust numbers)
MRC Ian
New Member
Magnum proof rounds hover in the 85K+ range, and many rifle manufactures torture test their designs with these off the shelf SAAMI loads. A .277 Fury proof load would be in the 106k+ range. With primer pockets typically opening up on brass proof rounds, I kind of doubt hand loaders have been pushing anything to this level and not knowing they're way over pressure.
In my experience I've had far more case head ruptures than actual receiver/action damage with proof loads. Winchester .308 proof loads have been the worst offender for me. The brass just can't handle it. On the other hand, I've fed a rifle 5 full boxes of 300 Win Mag proof loads just to see if I can break it... no dice.
If anyone wants to send me some reamers and proof rounds, I'd be happy to test it out
In my experience I've had far more case head ruptures than actual receiver/action damage with proof loads. Winchester .308 proof loads have been the worst offender for me. The brass just can't handle it. On the other hand, I've fed a rifle 5 full boxes of 300 Win Mag proof loads just to see if I can break it... no dice.
If anyone wants to send me some reamers and proof rounds, I'd be happy to test it out
cohunt
Well-Known Member
Aren't proof loads 1.5x a normal cartridge?Magnum proof rounds hover in the 85K+ range, and many rifle manufactures torture test their designs with these off the shelf SAAMI loads. A .277 Fury proof load would be in the 106k+ range. With primer pockets typically opening up on brass proof rounds, I kind of doubt hand loaders have been pushing anything to this level and not knowing they're way over pressure.
In my experience I've had far more case head ruptures than actual receiver/action damage with proof loads. Winchester .308 proof loads have been the worst offender for me. The brass just can't handle it. On the other hand, I've fed a rifle 5 full boxes of 300 Win Mag proof loads just to see if I can break it... no dice.
If anyone wants to send me some reamers and proof rounds, I'd be happy to test it out
nkyshooter
Well-Known Member
I'm loving the fact that what I hoped to come to understand is what is actually unfolding in the thread...
It seems nut vs tenon is not what is actually relevant. According to a response I just got from sig, "both the ammo AND the barrel" contain the pressure and they use "proprietary metals" for their barrels so only THEIR firearms can handle it.
Hmmm ... As an engineer I say BS.
Their response also says they "don't recommend" it in other firearms for that reason... No offense to any of you attorneys here but I'm thinking an attorney authorized that response ...
Everybody seems reluctant to say their actions or their barrels can handle it. I can understand the legitimate concerns over liability...
So it seems the actual weak(est) point is the case and in particular the case head. This is being addressed with the steel in the head. After that, the next weakest item needs to be strong enough over time and use to remain viable given the repeated use to 80k psi ... Seems that will be either the action or the barrel itself.
IF it's true modern bolt actions can handle that then it comes down to if the barrel can too ...
So this begs 2 questions:
1. How can ACTUAL (not attorney versions) realistic upper pressure limit of modern bolt actions be obtained?
And
2. How can ACTUAL realistic upper pressure limit of typical modern stainless steel barrels be obtained?
Note: even Excalibur is not immune... Their 277 fury chambered carbon fiber barrel specifically states 65k psi ...
The weak point is the case... The fury hybrid case attempts to resolve this
It seems nut vs tenon is not what is actually relevant. According to a response I just got from sig, "both the ammo AND the barrel" contain the pressure and they use "proprietary metals" for their barrels so only THEIR firearms can handle it.
Hmmm ... As an engineer I say BS.
Their response also says they "don't recommend" it in other firearms for that reason... No offense to any of you attorneys here but I'm thinking an attorney authorized that response ...
Everybody seems reluctant to say their actions or their barrels can handle it. I can understand the legitimate concerns over liability...
So it seems the actual weak(est) point is the case and in particular the case head. This is being addressed with the steel in the head. After that, the next weakest item needs to be strong enough over time and use to remain viable given the repeated use to 80k psi ... Seems that will be either the action or the barrel itself.
IF it's true modern bolt actions can handle that then it comes down to if the barrel can too ...
So this begs 2 questions:
1. How can ACTUAL (not attorney versions) realistic upper pressure limit of modern bolt actions be obtained?
And
2. How can ACTUAL realistic upper pressure limit of typical modern stainless steel barrels be obtained?
Note: even Excalibur is not immune... Their 277 fury chambered carbon fiber barrel specifically states 65k psi ...
The weak point is the case... The fury hybrid case attempts to resolve this
MRC Ian
New Member
33-49% for SAAMI, 25% for CIP in Europe (don't quote me on the CIP).
Whether or not a particular action can handle the Fury would have to be tested. There's too many variables to say for sure without doing so. Thankfully, cartridges and reamers are out there. Not sure if certified proof loads are yet.
As for SIG's statement of only our "special sauce" can handle it, as an engineer, I too call BS...
akmtnhnt
Well-Known Member
I know I've posted this here before, but here goes again.
Every modern full size action will take the bolt thrust of the sig fury. We know this because they already chamber magnum case head cartridges in those actions and math.
Source(lilja) - https://riflebarrels.com/a-look-at-bolt-lug-strength/
Bolt thrust = Area * Pressure
Area = Pi*(Inside case head Diameter/2)^2
277 fury = (Pi*(.385/2)^2) * 80,000 = 9313psi
7 PRC = (Pi*(.420/2)*2) * 65000 = 9005psi
Every modern full size action will take the bolt thrust of the sig fury. We know this because they already chamber magnum case head cartridges in those actions and math.
Source(lilja) - https://riflebarrels.com/a-look-at-bolt-lug-strength/
Bolt thrust = Area * Pressure
Area = Pi*(Inside case head Diameter/2)^2
277 fury = (Pi*(.385/2)^2) * 80,000 = 9313psi
7 PRC = (Pi*(.420/2)*2) * 65000 = 9005psi
nkyshooter
Well-Known Member
Thx akmtnhunt ...
THAT is the kind of analysis that I needed to have confidence in the action (for the bolt/lugs) ...
Is there similar to show that the receiver cylinder itself is not at risk?
Is there similar to show that a standard 1.060" stainless barrel is not at risk?
Thanks much in advance
THAT is the kind of analysis that I needed to have confidence in the action (for the bolt/lugs) ...
Is there similar to show that the receiver cylinder itself is not at risk?
Is there similar to show that a standard 1.060" stainless barrel is not at risk?
Thanks much in advance
MagnumManiac
Well-Known Member
Any rifle manufacturer and steel supplier…
nkyshooter
Well-Known Member
If you've got a link to such information, that would be useful.
MagnumManiac
Well-Known Member
Sorry, no links. Out of my pay grade.
ntsqd
Well-Known Member
If you condense this down to the "Free Body Diagram" it is a simple pressure vessel. It is oddly shaped for one of those, but that is what this is.
Hoop stress analysis using the thread's minor diameter as the OD of the barrel will reveal what it's absolute maximum pressure should be. Because there is necessary clearance in the threads in order to assemble the barrel to the action I do not see the receiver ring doing much as the barrel will need to 'grow' significantly from the pressure before it can contribute anything. Were the barrel a press-fit in the receiver ring this would be a different calculation (it would be far uglier).
Rather than trying to find what the stress is from some educated guess or other method of supplying an operating pressure I would suggest that instead the system be analyzed by looking for what the maximum pressure can be based on the properties of the barrel metal and it's geometry. From there a Factor of Safety can be applied to arrive at what the maximum pressure allowable should be.
Bolt thrust is fairly simple and semi-common calculation. Being conservative suggests ignoring any friction between the case body and the chamber wall. That friction is dynamic anyway, and we're looking for that minuscule slice of time at the peak stress. If the time span is narrow enough we can proceed as if this was a static condition. Ignoring the case to chamber friction is conservative as it builds in a bit more Safety Factor.
For the material properties needed in these calculations I'll suggest using Matweb's materials database. This sort of question is exactly what it is there for.
Hoop stress analysis using the thread's minor diameter as the OD of the barrel will reveal what it's absolute maximum pressure should be. Because there is necessary clearance in the threads in order to assemble the barrel to the action I do not see the receiver ring doing much as the barrel will need to 'grow' significantly from the pressure before it can contribute anything. Were the barrel a press-fit in the receiver ring this would be a different calculation (it would be far uglier).
Rather than trying to find what the stress is from some educated guess or other method of supplying an operating pressure I would suggest that instead the system be analyzed by looking for what the maximum pressure can be based on the properties of the barrel metal and it's geometry. From there a Factor of Safety can be applied to arrive at what the maximum pressure allowable should be.
Bolt thrust is fairly simple and semi-common calculation. Being conservative suggests ignoring any friction between the case body and the chamber wall. That friction is dynamic anyway, and we're looking for that minuscule slice of time at the peak stress. If the time span is narrow enough we can proceed as if this was a static condition. Ignoring the case to chamber friction is conservative as it builds in a bit more Safety Factor.
For the material properties needed in these calculations I'll suggest using Matweb's materials database. This sort of question is exactly what it is there for.
