Evening star. [volume] (Washington, D.C.) 1854-1972, 1893-06-17

case of the tube forging of one of the thirteen.
inch rifles tine powder chamber has a diameter
OF fifteen and one-half inches. The tube il
| first bored or 'roughed out" nearly to the fin.
Ished interior diameter. The outside is like.
/ wise turned on the lathe and smooth
machined' to the finished diameter. During
this operation the lathe is tended BY only two
! workmen-a mechanic and his helper The
smooth machining gives the surface of the
| gun a beautiful Clustering polish.
| Next the jacket forging is bored out inside to
a diameter slightly less than the exterior diame-
ter of the tube which it is destined TO eucircIe
Then 1t Is expanded by heat in a hot air furnace
| and, lifted carefully by means of a crane. ia
| placed directly above the tube which is stood
| upright in shrinking pit and securely held
with the breech upward. The jacket, heated
| not to white heat but only to an almost i'm
perceptible dull red. is then allowed to descend
accurately and clip down over the breech end
OF the tube-the expansion of the heated natal
OF the JACKET making this movement possible.
Notwithstanding the inner diameter of the
JACKET Is somewhat less than the outside diame-
ter OF the tube. As the jacket cools it prips
rightly over the tube aud Congresses IL
ms operation practically combines the
jacket and the tube into one piece. On
cooling. the jacket and tube together are
put In the lathe and the outside of the Jacket is
turned smooth 10 its finished dimensions.
Then the rorgings FOR the hoops are also bored
out TO dIameters slightly less than the respect-
~ bSA tAoIis VI gun WHICH tley are intended
70 enclrele. and one after another they are put
IN place by the same process that used in the
JacketIng. the metal gradually contracting as it
cools and COMPRISING the inner LAYERS firmly
Ia Its embrace. When all the hoops are on and
ali the parts put together the gun is again put
on the lathe and turned down over its whole
outside to the finished dimensions and likewise
finish bored on the inside to the exact diam
eter OF thirteen inches. The chamber is also
finished.
RIFLING THE GUN.
Ihereupon the gun is put into the rifing
machine and rihed. The interior surface of
tie bore is Gu. with fifty-two spiral grooves.
ich of which is $500 of an inch deep and
'.bout half an inch broad. Into these little
grooves will tit the projectile to be used which
Is enclrcled at is base with q soft copper band
OF diameter slightly larger than the caliber of
the gun. The action of the powder-charce
forces the projectile through the bore. and the
rih2d grooves. biting into this COPPER band.
give rotation to the projectile The rotation
lnsures greater accuracy in firing and has the
sui more important effect of keeping the pro-
1ectlie point headed foremost from the time it
leaves the muzzle until it strikes the object |
aimed at
The rifng process performed, the next step |
Is 10 nj The breech mechanism. In these thir- |
teea-lncn guns the breech mechanism has what |
Is Snown as the slotted screw; that is to saw, |
screw thread is cut in the rear part of the |
licket: and the breech plug which fits it is |
threaded to correspond. Alternate sections of |