79
RIFLE-BARREL STEEL, .30 CALIBER.
No. 7388.
Marks, M 3 A.
Exterior diameter, ".466.
Interior diameter, ".300.
Sectional area, .10 square inch.
Gauged length, 3".
I rom middle of length of finished barrel, rolled and annealed as usual.
Applied loads per square inch.	Elongation per inch.	Successive elongation per inch.	Permanent set.	Successive permanent set.	Remarks.
Pounds. 1,000 5,000 10,000	Inch. 0. .000100 .000300	Inch. 0. .000100 .000200	Inch. 0. 0.	Inch. 0. 0.	Initial load.
20,000	.000667	.000367			
30,000	.001033	. 000366			
40,000	.001367	. 000334			
50,000	.001733	.000366			
60,000 61,000	.002033 .002100	.000300 .000067	0.	0.	Elastic limit.
62,000	.022300	.020200			
63,000	.023667	. 001367			
64,000	.024667	.001000			
66,000	.026900	. 002233			
68,000 72,000	.029000	. 002100			
	.035833	.006833			
76,000	. 044000	.008167			
80,000	.053333	.009333			
84,000	.0767	.0234			
88.000	.1067	.0300			
90,200					Tensile strength.
					
.pounds.. 90,200
....do... 61,000
---inch.. .2200
....do... .002100
....do...	.116
. 1".26 from neck silky, cup-shaped
14.״ ,*26.״ ,*26.״ .
General summary.
Tensile strength per square inch of original section...
Elastic limit per square inch of original section......
Elongation per inch after rupture......................
Elongation per inch under strain at elastic limit......
Reduction in external diameter at point of rupture.....
Position of rupture....................................
Character of broken surface............................
Elongation of inch sections............................