I've heard that the REM 700 action will show pressure signs earlier than a custom action with a particular load, everything else being equal.
Can someone explain this?
Can someone explain this?
Gunsmithing REM 700 VS Custom action pressure ??
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Re: REM 700 VS Custom action pressure ??
It's B/S.
First understand that "pressure" is a term used very loosely in the gun community and it has a broad/sweeping definition in our little world.
We have two units:
Copper units of pressure (CUP)
Pounds per square inch (PSI)
CUP is essentially taking a copper cylinder of a known alloy and applying a load to it from a cartridge. The pressure developed by expanding gasses of the loaded cartridge press against the case and make it expand outward against the chamber. the copper stuck between gets smooshed and since copper/lead has almost zero elasticity strength it tends to stay put so it presents a reasonably accurate value. Through some calculations the amount of "smoosh" is then converted into a value. So when you see 50,000 CPU its not the same as 50,000 PSI.
From Wikipedia:
<span style="font-style: italic">Copper units of pressure or CUP, and the related lead units of pressure or LUP, are terms applied to pressure measurements used in the field of internal ballistics for the estimation of chamber pressures in firearms. These terms were adopted by convention to indicate that the pressure values were measured by copper crusher and lead crusher gauges respectively. This was necessitated by the adoption of more modern piezoelectric pressure gauges that more accurately measure chamber pressures and generally give significantly higher pressure values. <span style="text-decoration: underline"><span style="font-weight: bold">This nomenclature was adopted to avoid confusion and the potentially dangerous interchange of pressure values and standards made by different types of pressure gauges.</span></span> Pressure is a fundamental thermodynamic parameter that is expressed in units of force divided by area. In the avoirdupois system, the units of pressure are pounds per square inch and in the metric system, the units or pressure are newtons per square meter (pascals). A chamber pressure measured with a copper crusher gauge would be expressed as psi (CUP) in the English system or MPa (CUP) in the metric system.</span>
Believe it or not a factory Remington 700 action is good to only around 3,500 <span style="font-weight: bold">psi</span> before it'll fail. WHAT? I know crazy huh? What I'm talking about is the actual pressure rating of the receiver in actual pounds per square inch; not a barrel and receiver screwed together firing a cartridge that peaks for but a few milliseconds and quickly returns back to ambient. I'd lay dollars to doughnuts a custom action isn't much different. The only way you increase this rating is by adding mass to the receiver and/or with a material change/heat treatment. The practicality of going overboard mitigates actions resembling Howitzers.
Talk to anyone who works in big oil. Pressure vessel fittings are substantially more robust than our puny actions, yet they are only rated to around 10-15 kpsi.
Bottom line is the cartridge has no way of knowing what receiver its in. Now there are things that can/will show signs if ignored. The top of the list is probably striker/striker hole tolerances that are on the loose side.
Remingtons often have a striker hole on the bolt face that is much larger than really needed. If you start gassing up a load it's not uncommon to experience some cratering-a cardinal rule of excessive case pressure.
But in this case it's a false signal. If we bush the striker hole and/or shoot the same cartridge out of a custom action with a more conservative clearance it's very reasonable to expect the pressure sign goes away.
Is the custom action stronger/better? In a sense yes it is as the manufacturer paid more attention to detail. In reality no it's not necessarily stronger as the Remmy can be modified to achieve the same thing.
Make sense?
Hope this helped.
C.
It's B/S.
First understand that "pressure" is a term used very loosely in the gun community and it has a broad/sweeping definition in our little world.
We have two units:
Copper units of pressure (CUP)
Pounds per square inch (PSI)
CUP is essentially taking a copper cylinder of a known alloy and applying a load to it from a cartridge. The pressure developed by expanding gasses of the loaded cartridge press against the case and make it expand outward against the chamber. the copper stuck between gets smooshed and since copper/lead has almost zero elasticity strength it tends to stay put so it presents a reasonably accurate value. Through some calculations the amount of "smoosh" is then converted into a value. So when you see 50,000 CPU its not the same as 50,000 PSI.
From Wikipedia:
<span style="font-style: italic">Copper units of pressure or CUP, and the related lead units of pressure or LUP, are terms applied to pressure measurements used in the field of internal ballistics for the estimation of chamber pressures in firearms. These terms were adopted by convention to indicate that the pressure values were measured by copper crusher and lead crusher gauges respectively. This was necessitated by the adoption of more modern piezoelectric pressure gauges that more accurately measure chamber pressures and generally give significantly higher pressure values. <span style="text-decoration: underline"><span style="font-weight: bold">This nomenclature was adopted to avoid confusion and the potentially dangerous interchange of pressure values and standards made by different types of pressure gauges.</span></span> Pressure is a fundamental thermodynamic parameter that is expressed in units of force divided by area. In the avoirdupois system, the units of pressure are pounds per square inch and in the metric system, the units or pressure are newtons per square meter (pascals). A chamber pressure measured with a copper crusher gauge would be expressed as psi (CUP) in the English system or MPa (CUP) in the metric system.</span>
Believe it or not a factory Remington 700 action is good to only around 3,500 <span style="font-weight: bold">psi</span> before it'll fail. WHAT? I know crazy huh? What I'm talking about is the actual pressure rating of the receiver in actual pounds per square inch; not a barrel and receiver screwed together firing a cartridge that peaks for but a few milliseconds and quickly returns back to ambient. I'd lay dollars to doughnuts a custom action isn't much different. The only way you increase this rating is by adding mass to the receiver and/or with a material change/heat treatment. The practicality of going overboard mitigates actions resembling Howitzers.
Talk to anyone who works in big oil. Pressure vessel fittings are substantially more robust than our puny actions, yet they are only rated to around 10-15 kpsi.
Bottom line is the cartridge has no way of knowing what receiver its in. Now there are things that can/will show signs if ignored. The top of the list is probably striker/striker hole tolerances that are on the loose side.
Remingtons often have a striker hole on the bolt face that is much larger than really needed. If you start gassing up a load it's not uncommon to experience some cratering-a cardinal rule of excessive case pressure.
But in this case it's a false signal. If we bush the striker hole and/or shoot the same cartridge out of a custom action with a more conservative clearance it's very reasonable to expect the pressure sign goes away.
Is the custom action stronger/better? In a sense yes it is as the manufacturer paid more attention to detail. In reality no it's not necessarily stronger as the Remmy can be modified to achieve the same thing.
Make sense?
Hope this helped.
C.
Re: REM 700 VS Custom action pressure ??
wow... I just learned a lot.
So just a quick question. If i have a standard remington 700 action in comparison to a trued remington 700 action (obviously has tighter tolerances), could it be theoretically possible to shoot a "hotter" load? Please excuse my ignorance if i may have missed the obvious answer.
wow... I just learned a lot.
So just a quick question. If i have a standard remington 700 action in comparison to a trued remington 700 action (obviously has tighter tolerances), could it be theoretically possible to shoot a "hotter" load? Please excuse my ignorance if i may have missed the obvious answer.
Re: REM 700 VS Custom action pressure ??
No, to see a difference in "pressure capability" of an action you need to make design changes. Simply taking a 700 and removing material to "true" up the surfaces will not do this.
The limiting factor many times is the case head design, although receiver design is coupled as well.
Bottom line is, a Remington or Remington clone can take a certain pressure level in the action for a certain case. Bigger case heads dictate higher bolt thrust loads and less material radially around the case.
Stress state is not always the driving design factor on receiver "strength". Looking at stresses will simply tell you if the bolt is going to shear lugs and kill you that way. It is not a good way to develop an action for everything that a precision rifle needs to do.
No, to see a difference in "pressure capability" of an action you need to make design changes. Simply taking a 700 and removing material to "true" up the surfaces will not do this.
The limiting factor many times is the case head design, although receiver design is coupled as well.
Bottom line is, a Remington or Remington clone can take a certain pressure level in the action for a certain case. Bigger case heads dictate higher bolt thrust loads and less material radially around the case.
Stress state is not always the driving design factor on receiver "strength". Looking at stresses will simply tell you if the bolt is going to shear lugs and kill you that way. It is not a good way to develop an action for everything that a precision rifle needs to do.
Re: REM 700 VS Custom action pressure ??
C.Dixon thanks for shedding light on the subject.
C.Dixon thanks for shedding light on the subject.
