53
12-INCH steel b. l. rifled mortars.
Tube.
No. 7303.
Marks,
Diameter, ".564.
Sectional area, .25 square inch. Gauged length, 3".
Applied loads per square inch.	Elongation per inch.	Successive elongation per inch.	Permanent set.	Successive permanent set.	Remarks.
Pounds.	Inch.	Inch.	Inch.	Inch.	
1,000	0.	0.	0.	0.	
5,000	.000067	.000067			
10,000	.000333	.000266			
20,000	.000667	. 000334			
30,000	.001000	.000333			
35,000	.001167	.000167	. 000033	.000033	
40,000	.001367	.000200	.000033	0.	
51,000	.001700	.000333			Elastic limit.
52,000	. 001933	. 000233			
53,000	. 002333	.000400			
54,000	.003267	.000934			
55,000	. 004000	.000733			
56,000	. 004667	. 000667			
90,400					Tensile strength.
General summary.
Tensile strength per square inch of original section.............................pounds.. 90,400
Elastic limit per square inch of original section........... ......................do... 51 000
Elongation per inch after rupture..................................................inch. . io33
Elongation per inch under strain at elastic limit..........................’ ....**. .do.!! . 001700
Position of rupture.......specimen not fractured; stripped thread on’head!’*The’head was too
short to give adequate strength for testing.