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Posted: 12/23/2008 9:12:12 AM EDT
| with all the talk of chrono's lately. how does a simple person such as i determine what my round pressure is . if its long complicated or just to damn complex i'll let it pass and stick to the load data and chrono |
| I'm fairly sure it involves some serious equipment that a normal person does not have access to. I could be wrong though. Knowing the number isn't important. Do you know what pressure signs to look for on your fired brass to indicate overpressure? That's all that really matters. |
| yes i know the pressure signs as what to look for although when it comes to primers and i shoot a colt 6721 & rra entry tactical both 5.56 my reloaded primers are flattened just the same as my factory are they look identical. and i know im well below the max with 24-25 grns of AA2230 in my boolits |
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Quoted:
with all the talk of chrono's lately. how does a simple person such as i determine what my round pressure is . if its long complicated or just to damn complex i'll let it pass and stick to the load data and chrono Some people use the condition of the fired primer, but that is very unreliable. Some people micrometer the brass at the case web, and look for sudden increases in dimension but that is tricky to measure accurately. I prefer to use a chrono and keep my loads in the expected velocity range for the bullet, powder, caliber combination and to watch for erratic velocity. This is indirect as velocity is a function of the area of the pressure curve, not its peak but easier to do. |
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First, to measure the pressure accurately you have to drill a hole in your barrel either in the chamber or just before the rifling. Do you want to drill a hole in your barrel? Next you have to tap that hole to accept a fixture that has a plunger that compresses either a piezo-electric transducer or a bit of calibrated copper. Then you need equipment to read the pressure from the transducer or micrometer to measure the bit of copper.
There is another way that involves mounting strain gauges to one's barrel. This is not destructive to the barrel. You still need instruments to read the change in resistance of the strain gauges that are quick and sensitive enough to see the expansion in barrel while the powder charge is burning. These are available to the serious handloader. The pressure reading that you get with these are not SAMMI compareable. They do give one a good idea of the pressure curve and whether a load has aspects that may tend to make it unsafe. Still, you will have wires that need to be connected to the data logger hanging from your firearm. If you want to use this rifle for other things than pressure testing on a bench, then you will need to somehow protect the wires and the strain gauges from damage. If you remove the gauges you will need to reapply new ones. These new gauges will very likely have slightly different characteristics. Your data obtained earlier will not necessarily correspond to your new set. This is why most handloaders do not opt to measure their own pressure. The chronograph along with loading manuals do tell us whether our loads are getting on the dangerous side before something catestrophic happens. |
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Quoted:
First, to measure the pressure accurately you have to drill a hole in your barrel either in the chamber or just before the rifling. Do you want to drill a hole in your barrel? Next you have to tap that hole to accept a fixture that has a plunger that compresses either a piezo-electric transducer or a bit of calibrated copper. Then you need equipment to read the pressure from the transducer or micrometer to measure the bit of copper. There is another way that involves mounting strain gauges to one's barrel. This is not destructive to the barrel. You still need instruments to read the change in resistance of the strain gauges that are quick and sensitive enough to see the expansion in barrel while the powder charge is burning. These are available to the serious handloader. The pressure reading that you get with these are not SAMMI compareable. They do give one a good idea of the pressure curve and whether a load has aspects that may tend to make it unsafe. Still, you will have wires that need to be connected to the data logger hanging from your firearm. If you want to use this rifle for other things than pressure testing on a bench, then you will need to somehow protect the wires and the strain gauges from damage. If you remove the gauges you will need to reapply new ones. These new gauges will very likely have slightly different characteristics. Your data obtained earlier will not necessarily correspond to your new set. This is why most handloaders do not opt to measure their own pressure. The chronograph along with loading manuals do tell us whether our loads are getting on the dangerous side before something catestrophic happens. And to think i thought it was only going to be a complex mathematical formula yes ill stick with my chronograph( as grazed as she is) and load data 
and yes it still works fine |
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Quoted:
First, to measure the pressure accurately you have to drill a hole in your barrel either in the chamber or just before the rifling. Do you want to drill a hole in your barrel? Next you have to tap that hole to accept a fixture that has a plunger that compresses either a piezo-electric transducer or a bit of calibrated copper. Then you need equipment to read the pressure from the transducer or micrometer to measure the bit of copper. There is another way that involves mounting strain gauges to one's barrel. This is not destructive to the barrel. You still need instruments to read the change in resistance of the strain gauges that are quick and sensitive enough to see the expansion in barrel while the powder charge is burning. These are available to the serious handloader. The pressure reading that you get with these are not SAMMI compareable. They do give one a good idea of the pressure curve and whether a load has aspects that may tend to make it unsafe. Still, you will have wires that need to be connected to the data logger hanging from your firearm. If you want to use this rifle for other things than pressure testing on a bench, then you will need to somehow protect the wires and the strain gauges from damage. If you remove the gauges you will need to reapply new ones. These new gauges will very likely have slightly different characteristics. Your data obtained earlier will not necessarily correspond to your new set. This is why most handloaders do not opt to measure their own pressure. The chronograph along with loading manuals do tell us whether our loads are getting on the dangerous side before something catestrophic happens. The visibility of Pressure Trace strain gages is all up the creativity of the user. Many have been installed under the stock and are invisible. While there isn't 1:1 agreement with SAAMI standards, using a range of factory ammo in an otherwise standard SAAMI chamber/throat WILL provide more than adequate safety for the reloader. And more importantly, the determination of ill-behaving reloads is readily established, often times better than piezo transducers. |
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