Mike W1
08-08-2015, 12:57 PM
Have a LBT tester from when he was still in AZ so I've had it awhile. Been testing some sample's and thought it might not be a bad idea to read things over again. Amazing how much I'd forgotten including it's a good idea to take 3 readings and average. However here's some points the author made that might give you guys all something to argue about!
"For maximum accuracy, calculate the average for at least three readings.
BE SURE TO MOVE PENETRATOR TO A DIFFERENT SPOT FOR EACH TEST, KEEP INDENTS SPACED
FAR ENOUGH APART THAT COLD WORKING OF FIRST INDENT DOES NOT INFLUENCE
SUBSEQUENT READINGS.
Space 1/16 inch apart for hard alloys, 1/8 or more for softer alloys.
If the first reading is lower than subsequent readings, disregard it. Even with extreme care in flattening bullet
bases and hand crushing any remaining smal1 flaws the first reading is normally lower than average.
Lead alloy hardness is determined more by cooling rate and ageing temperature and time, than by alloy content,
consequently, hardness readings cannot be used to determine alloy content.
Lead alloy hardness constantly fluctuates with temperature, approximately 4 bhn within the temperature range
of 0 to 100 deg F, softening at higher temperatures, and hardening at lower temperatures.
Regardless of alloy type, bullet hardness is virtually identical all the way through. No alloy or method of
hardening will produce a hard ‘skin’, and softer core, as many believe.
Hardness of air cooled, large diameter bullets can vary up to 2 bhn from side to side due to uneven cooling.
We have never encountered hardness variations within individual bullets that had been cooled by water
quenching, whether quenched after casting or heat treatment."
"For maximum accuracy, calculate the average for at least three readings.
BE SURE TO MOVE PENETRATOR TO A DIFFERENT SPOT FOR EACH TEST, KEEP INDENTS SPACED
FAR ENOUGH APART THAT COLD WORKING OF FIRST INDENT DOES NOT INFLUENCE
SUBSEQUENT READINGS.
Space 1/16 inch apart for hard alloys, 1/8 or more for softer alloys.
If the first reading is lower than subsequent readings, disregard it. Even with extreme care in flattening bullet
bases and hand crushing any remaining smal1 flaws the first reading is normally lower than average.
Lead alloy hardness is determined more by cooling rate and ageing temperature and time, than by alloy content,
consequently, hardness readings cannot be used to determine alloy content.
Lead alloy hardness constantly fluctuates with temperature, approximately 4 bhn within the temperature range
of 0 to 100 deg F, softening at higher temperatures, and hardening at lower temperatures.
Regardless of alloy type, bullet hardness is virtually identical all the way through. No alloy or method of
hardening will produce a hard ‘skin’, and softer core, as many believe.
Hardness of air cooled, large diameter bullets can vary up to 2 bhn from side to side due to uneven cooling.
We have never encountered hardness variations within individual bullets that had been cooled by water
quenching, whether quenched after casting or heat treatment."