...It seems like the guage would impact pressure, and a 16 ga at 3 tons and a 12 ga at 3 tons would need to take different pressures, or the 16 ga would need thicker or stronger barrels?
Pressure does not equal recoil, because recoil is measured in foot pounds.
U.S. manufacturers are not as concerned with pressure because they are trying to meet a different standard i.e. FPS, and change powders from time to time resulting in different pressures, but the same FPS.
....It sounds like there is a mimimum standard the Brits are trying to meet for all guns. For that matter same goes for U.S. guns, and maybe guns imported for use in U.S.?
Ok, 1st, I am not going to even touch the CIP/BAR/TON/PSI/PIEZO/CRUSHER discussion...the relationship is a curve so a simple linear expression will not be accurate in all instances.
Recoil and pressure are related. However, the relationship is complex. The calculation to arrive at chamber pressure includes many more variables. Perhaps a definition of pressure is needed. From the SAAMI website:
PRESSURE
In a gun or cartridge, the force imparted to various components that is developed by the expanding gases generated by the deflagration of the propellant when fired.
So you press the trigger and a lot of energy is released. Where is going? Up the barrel? Well only to a degree, few things are 100% efficient.
WHERE DID IT GO?
A pound of single-base rifle powder has an energy content of about 1,246,000 ft-lbs of energy or about 178 ft-lbs per grain of powder. In actual practice only a fraction of this energy is available to accelerate the bullet. Julian Hatcher in HATCHER'S NOTEBOOK reported the energy distribution for the Browning Machine Rifle as follows:
Heat to cartridge case 4%
Kinetic energy to bullet 29%
Kinetic energy to gases 19%
Heat to barrel 22%
Heat to gases 19%
Heat to bullet friction 7%
Total = 100%
You will note that the energy imparted to the bullet is only about 29% of the total powder energy available. While this is typical of many small arms cartridges, actual efficiencies may range from 17 to 37 percent or more. The actual efficiency is basically a function of expansion ratio and charge weight to bullet weight ratio.
As you can see, one event causes multiple responses. Gun powder is burnt. Gases are released. The load begins to move. The barrel starts to flex in 3 dimensions. Heat is generated.
Part of this is measured in recoil. A simple law of Newtonian physics, "For every action there is a reaction". But something more complex is occurring. In part the burn rate of the powder, not just how many grains you used, plays a role in determining pressure. Think of it this way. If you are lighting a BBQ and all you have is some paper, the flame takes a while to get going. Soak a little starter fluid on the paper and it burns at a very different rate. With gun powder the size, shape and detergent coatings play a role in determining the burn rate. Did you ever look a burn rate chart? They are very informative:
http://www.reloadbench.com/burn.htmlhttp://www.reloadersnest.com/burnrates.aspAmmunition manufacturers use very precise calculations to determine the loads they develop. Then they do a lot of pressure tests and chronographing of the projectile. They walk a thin line. Their goal is to produce a load with a certain muzzle velocity while keeping the pressure within SAAMI standards.
They are dealing with a working pressure that has been established, requiring that the powder burning rate (relative quickness) be matched to load acceleration to produce optimum velocity. For a given pressure the optimum velocity can only be obtained by maintaining the accelerating force for a longer or shorter period of time.
To think that the British companies have a different objective than American, than Italian, than German is not true. They are all relying on the same buyer. What is true is a relatively small percentage of shooters choose to shot a 100 year old gun with 2 barrels that was proofed using methods no longer in use. Most prefer a semi-automatic and Wally World Wonder Shells.
Pete
