STRESSES IN GUN FORGINGS. 
99 
limit 9 in action, and its value will be found from equation 
(1) (Appendix B, “ Gun Making ”); whence 
Breech: P- (, + *) = X 120000 = 
70000 pounds per square inch. 
44 09 
Breech middle: P— X = 71652 pounds per 
'square inch. 
The muzzle middle and muzzle sections are less than 0.65 
caliber thickness, being respectively 0.45 and 0.22 caliber. 
The desired initial compression, or that value of p, in terms 
of the limit 9, which will cause the wall to be uniformly 
strained to 60,000 pounds per square inch when the limit of 
interior pressure is reached, is found by combining equa¬ 
tions (1) and (2) of the work cited; whence 
|- 4 R> + 2 jy 
L_3 ( 
From which we find: 
Muzzle middle : p — 0.6769 X 60000 = 40614 
Muzzle : P = 0.3174 X 60000 = 19046 
These reduced values of p being given, the maximum re¬ 
sistance will be found by applying equation (1) as for the 
other sections. Then 
Muzzle middle: P — (40614 -f- 60000) = 47650 pounds 
per square inch. 
ft i q 
Muzzle : P — (19046 + 60000) = 24634 pounds per 
Zv.Zo 
square inch. 
The value 24,634 for the muzzle section is less than 24,920, 
which was computed, from the most dangerous one of the 
actually measured stresses, to be the resistance after anneal¬ 
ing. This slight discrepancy is due to the irregularities of 
