Notes on Development Type Materiel

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NOTES ON
DEVELOPMENT TYPE MATERIEL
Gun, Machine, Light, Cal. .30 T-52-E3
1here is no copyrighted matter contained
in this report.
ORDNANCE DEPARTMENT
Philadelphia Ordnance District
Philadelphia, Pennsylvania
Prepared by
BRIDGE TOOL AND DIE WORKS
738 South Forty-second Street
Philadelphia 4, Pennsylvania
Government Contract No. DA-36-034-0rd-87
February 1952
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(Appropnate da::;sliicJ.tion) (event)
NOTES ON
DEVELOPMENT TYPE MATERIEL
for
GUN , MACHINE, LIGHT , CAL . . 30 T-52-E-3
TABLE OF CONTENTS
Chapter I - INTRODUCTION
1. Scope ... ... ... .. ... .. .. .. .. ....... .... .. .. .... .... .. ......... ...... .. ... .... 1
2. Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
3 Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
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References ...... ..... .......... ..... ... ............ ... .... ..... ... .. ........ 1
Chapter II .. DESCRIPTION AND OPERATION
5. Receiver Group .. ....... ....... ........ ..... ... .......... ......... .. ..... .... 2
6. Front Sight . .... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
7. Gas Cylinder Group ... .... ........ ... .. .. .. ... .. ... ...... .... ...... ..... .. .... 2
8 Operating F.od and Bolt Group ..... .... .... .... ........... ............. ........ 3
9. Driving Spring Group.. . .. ... ..... ... ... .. .............. .. .... .. ............. 4
10. Recoil Buffer Group ... ... ...... ......... ...... .......... .... ... ............. . 4
ll. Feeding rv'rechanism Group.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
12 Trigger Mechanism Group .......... ....... ... .. ......... .. ...... ...... ... ... ... 6
13 Barrel and Barrel Lock Group .. .. ... ........... .. ... .............. .. .... ..... . 6
14 Stock Group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
15. Tripod Mount. . . . . . . . . . . . . . . ... ·. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Chapter III - DISASSEMBLY AND ASSEMBLY
16. General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
17. Disassembly into Major Parts and Subassemblies ....... ... .. ............ ...... 11
18 Cover, Feed Mechanism Group .. ... .... ... ............ ..... .. .... ........... ... 11
19. Feed Plate Removal .... ... ... .. ........... .... .................. .... ......... 11
20. Stock Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
21 Recoil Bnffer Group... .... .. ... . ......... ... ...... .. .. .. ....... ............ 11
22. Driving Spring.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
23 · Operating Rod and Bolt ... .. ..... .. ... .. ................ .. ....... ..... ....... 12
24 Cocking Handle Removal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
25 Barrel Removal Group .. .. .... ......... ................ .. ........... .......... 12
26. Forearm and Carrying Handle. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
27. Trigger Mechanism Group.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
28. Barrel Lock Group ...... .. .............. .......... .. .. ... ......... .. .. ....... 13
29. Disassembly of Subassemblies (Para. 30 to 39 Inc.) ............ ......... .. ... 13
30. Operating Rod and Bolt .. .. ...... ....... ..... ......................... .... ... 13
31. Operating Rod Group ... ... ...... ...... .. .. .............. .... ...... ..... ...... 13
32. Bolt Group ...... ..... ......... ..... ..... .... .... ...... .... ..... ....... ...... 13
33. Cover, Feed Mechanism Group ... ................... ......... ...... ... ........ . 17
34. Rear Sight ... .... ....... ......... ....... ...... ..... ... .. ...... ...... .... ... . 17
35 Recoil Buffer Group.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
36. Trigger Mechanism Group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
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Chapter III ·· DISASSEMBLY AND ASSEMBLY (Continued)
37. Barrel Group ...... ... .......... .... ................ ...... .. ... .... .... .. .... 21
38. Bipod Group ........ , ...... ..... ..... ............. .... ... ..... ..... ..... ..... 21
39. Receiver Housing Group .... ..... .... ........... ...... ........................ 24
40. Assembly of Subassemblies (Para. 41 to 48 Inc.) ......... ...... ... ........... 24
41. Bolt Group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
42. Operating Rod Group .. .......... .. ........ ............. .. ...... ..... .... .... . 24
43 Operating Rod and Bolt Group ... .. .. .... .. ............ .. ......... .......... .. 24
44. Trigger Mechanism Group ........ .. .. .... ... ......... ........... ....... .... ... 25
45. Recoil Buffer Group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
46. Rear Sight ...... ... .................... .................. .... .............. 26
47 . Cover, Feed Mechanism Group ...................... .......... ....... ..... .. ... 29
48. Barrel Group ............ ........... ............ .. .. ................... .. ... . 29
49. Gun Assembly from Subassemblies and Major Parts (Para. 50 to 59 Inc.) ... .... 30
50 . Receiver Housing Group. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
51. Trigger, Carrying Handle and Forearm Group ....................... .......... . 33
52. Barrel Group .... ... ....... ·. . ... .. .......... .... .............. ... .... ..... ... 33
53. Cocking Handle ..... .... .. ......................... .... .. ..... ......... ..... ... 33
54. Operating Rod and Bolt .. ........... ..... ...... ..... .................. ....... 33
55. Driving Spring Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
56. -Recoil Buffer Group .. ..... .......................................... .... .... 33
57. Stock Assembly ...... .. .. ....................................... ............. 34
58. Feed Plate .. .... ........................ .. .... .............. ... ... ... ....... 34
59. Cover, Feed Mechanism Group .................... .... .... ....... ...... ..... ... 34
60. Loading of G~,tn. . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
61. Alternate Method of Gun Loading .. .... .... ... ...... ................. ......... 36
APPENDIX
a. List of Drawings .... .. .... ........ ................... ...... ........... ...... 38
b. Spare Parts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
c. Photographs and Prints
1. Fig. 1 - Recoil Buffer Assembly .................. ......... .............. 5
2.. Fig. 2 - Cover Assembly ..... .. ..... .. ..... ..... .... .... ......... ... ... .. 7
3. Fig. 3 Cover Open and Barrel Removed ...... .. ........ ............ .. .... 8
4. Fig. 4 .. Disassembled View .. ..... ........ ... .. ............. ... .... ...... 10
5. Fig. 5 ·· Operating Rod and Bolt Assembly .. ... .......................... 14
6. Fig. 6 .. Operating Rod Assembly ................................. ..... .. 15
7. Fig. 7 ·· Bolt Assembly ...... ......................... ....... .......... 16
8. Fig. 8 - Rear Sight Assembly .. ... .. ...... ... ..... ........ .. ...... ...... 18
9. Fig. 9 - Trigger Mechanism Assembly ........ ...... ... ........ ........... 20
10. Fig. 10 · Barrel Final Assembly. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
11. Fig.ll · Bipod Assembly, Std .... ........... ........ ................... 23
12 Chart 1 ·· Elevation Data for Rear Sight ............... .... ... ....... ... 27
13. Chart 2 - Windage Data for Rear Sight .. ............. ... .. .. .. ........ .. 28
14. Fig. 12 - Gun, Main Assembly: .......................... ................ 31
15. Fig. 13 - Receiver Assembly .. .. .............. .......................... 32
16. Fig. 14 ·· Cover Closed,- Bipod Mounted .... ..... .. ...... .............. .. 35
17. Fig. 15 ·· Heavy Barrel· and Cartridge Belt in Place .... .... ......... .... 37
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CHAPTER I
INTRODUCTION
1. SCOPE
a. These Notes on Materiel are for the purpose of describing for Ordnance and
Service Personnel the source, operation, and parts of the Model of the Light,
Automatic Machine Gun Cal .. 30 T-52-E3. which will hereinafter be referred
to as the Gun.
2. SOURCES
a. The Gun is a progressively irnpro-,ed model based upon the Cal. 7 92 MM T-44
experimental gun, the further modified Cal. . 30 T-52 experimental gun, and
the further modified Cal .. 30 T-52-El Experimental gun, with varying modifi
cations as requested by the Office Chief of Ordnance, Research and Develop
ment Service, Artillery Small A:rms Branch, Washington, D. C.
b. The Gun was developed by Bridge Tool and Die Works, Engineering Division,
Philadelphia, Pennsylvania, for the Office Chief of Ordnance, Research and
Development Service, A'ltillery Small Arms Branch, Washington, D. C.
3. CHARACTERISTICS
a. Gas Cutoff and Expans;.on System of Operation.
b. Aircooled.
c. Fast Change Barrel.
d. Bipod Supported.
e. Provisions made for Tripod Mount.
f. Employs T -65 Cartridge with cli sintegrating Link.
g. Cyclic rate of fire - approx. 700 per min.
h. Total weight - 20 lbs
• i . Light Barrel Weight bare ·· 3~ lbs.
j. Heavy Barrel WP-ight bare - 7 lbs
k. Length - 43~" with flash suppressor.
4 . REFERENCES
a. Photographs and line drawings, taken in various positions to aid in identi
fying parts, are insert.P.d throughout the book.
b. In the appendix is listed the assemblies, detailed drawings, and spare parts
of the Gun.
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CHAPTER II
DESCRIPTION AND OPERATION
5. RECEIVER GROUP
a. The receiver body, in which the essential parts of the Gun operate, is of
spot welded, sheetmetal construction, consisting of an inner and outer hous
ing, one bridge member, and a machined socket The forward end of the socket
supports the barrel retaining pin
b. The inner and outer housings, spot welded together, form ~ channel-shaped
section, which supports the operating rod and bolt. The receiver has a longi
tudinal opening 1/2" wide along the top side, through which the operating
rod protrudes to operate the feeding cam. The 1/2" wide opening is maintained
by welding the assembled housings in the machined socket and spot welding the
bridge member sparming the opening.
c. Holding the receiver in a normal firing position, on the right side is a
formed metal track in the ou~er housing, running from the socket in the front
to within 5 1/4" from the rear of the receiver housing, which contains, the
cocking handle. The cocking handle, on being drawn rearward, engages the op
erating rod and cocks the Gun. It is then free to move forward and to be held
in a forward position by a spring contained in the cocking handle.
d. The trigger mechanism group is mounted on the underneath side of the rece1ver
and interrupts the operating rod to control firing.
e. The sheet metal, rubber coated, forearm group is mounted on the forward end
of the receiver housing and is retained in position by the same pin that
locks the trigger mechanism group in its position.
6. FRONT SIGHT
a. The muzzle end of the barrel accommodates the assembly of the front sight.
b. The front sight is rigid and held in radial and longitudinal alignment with
barrel, by taper pins.
c. A protrusion on front loop of sight extends through bipod mount and engages
slots on flash suppressor to lock i t in place.
7. GAS CYLINDER GROUP
a. The gas cylinder is tubular· in appearance and is mounted beneath the forward
end of the barrel. Two (2) loops are provided which slip over the barrel and
retain the entire assembly. The cylinder is ported through to the barrel with
a .120 diameter hole mating with an .093 diameter orifice in the barrel. On
the underneath side and in the center of the gas cylinder is a row of four
(4) equally spaced exhaust port openings to exhaust the gases before the
action returns the piston to the firing position. There are three (3) holes
located 3/8" from rear end of gas cylinder for drainage purposes.
b. The rearward end of the gas cylinder has a small diameter pin to retain the
piston when barrel is out of the Gun.
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c. The forward end of the gas cylinder is threaded for a plug, which permits
assembly and the cleaning of the cylinder and piston
d. The piston is a true diameter for its full length, unguided and floats when
in operation. It is hollowed out to reduce Its weight and to provide space
for gas expansion. Gas enters the piston through seven port holes connected
by an annular ring
e. The gas cylinder group <eceives a metered quantity of gas from the barrel
into the hollow piston, which when full, moves rearward, thus cutting off the
port opening between the piston and cylinder. This trapped gas then expands,
imparting movement to the piston operating rod and bolt group.
8. OPERATING ROD AND BOLT GROUP
a. The operating rod is tubular in appearance, closed on the forward end. The
rear end has two (2) projections upward The extreme rear projection pro
vides for guiding the bolt a~d imparting motion to the feed mechanism cam.
The other projection extends i~to the bolt, through the cam opening, to con ..
trol the bolt movement and rotation It also has a locating hole to accommo
date the firing pin spring guide The underneath side of the operating rod is
machined in such a manner that the sear will either lock it and hold back, or
permit it to ride over depending upon the position of the trigger. The for
ward end of the operating rod is machined smaller in diameter to extend into
the rear of the gas cylinder. to position the p:iston. The operating rod has
two (2) shallow retaining ledges machined on the forward end to accommodate
the cocking handle and ope;ating rod safety lever, thus supplying the means
for cocking the Gun and fo·· pre·;ei:ting the operating rod and bolt assembly
from going forward and damag:ing the feed plate when the barrel assembly is
removed from the recei"ler, and ,-,he trigger pulled accidently.
b. The operating rod and bolt assembly are inserted into the rear of the receiv
er housing with the bolt ln the top guide rails of the housing. It is po
sitioned radially by c~ms, protruding from the forward end of the bolt, which
ride in rectangular sections of the receiver housing, thereby permitting the
bolt a guided forwaLd movement
c. Motion is imparted to the holt by inserting the operating rod projection into
a cam opening through the side of the holt. at its midsection, and by acting
against this cam surface. r·otates the bolt in the locking rings of the barrel.
By this rotary action the protruding cams on the forward end of the bolt lock
and inversely unlock in the barrel locking rings
d. The firing pin is retained in the forward end of the bolt. It is actuated by
a hammer blow imparted to it. by the projection on the operating rod. The fir
ing pin spring is 8onfined by the firing pin spring guide located on pro
jection of operating rod. and the rear end of the firing pin spring is se
cured to the rear portion of the bolt by the bolt extension and bolt exten
Sion p1n.
e. The function of the firing pin spring is to impart energy into the firing
pin. The firing pin spring causes the operating rod to move forward striking
the firing pin, thus firing the primer.
f. The extractor parts are fit ted into a milled slot located on the side and
forward portion of the bolt The cartridge extractor, by spring pressure, en
gages the rim on the cartridge case, and as the bolt is moving rearward,
withdraws the cartridge case from the barrel.
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g. Ejection is accomplished by a spring loaded ejector. mounted on the left side
of the receiver housing, riding into a slot on the side of the holt striking
the base of the cartridge case as the bolt moYes rearward and forcing the
fired case out an opening in the right side of the receiver housing.
9 . PRIVING SPRING GROUP
a. Insert round end of driving spring guide into driving spring, then the free
end of spring into the hole in the rear of operating rod .. Compress and retain
driving spring within operating rod by assembling recoil buffer on rear pro
jection of driving spring guide. Its function is to store energy, developed
during the rearward travel of the bolt to be used to drive th~ holt forward,
thus starting the firing cycle
10 . RECOIL BUFFER GROUP
a. The recoil buffer group is mounted into the lower portion of the rear end of
the receiver housing. its position being directly rearward of the operating
rod, thereby, confining between the two, the driving spring. The recoil buffer
is inserted into the receiver housing and rotated through ninety (90°) degrees
to lock in position. The recoil buffer latch spring then positions itself into
the receiver body, resisting any turning movement of the recoil buffer, unless
the recoil buffer latch spring is, in turn, depressed.
b. The recoil buffer body houses the driving spring guide retainer which is
shouldered against the forward end of the recoil buffer body, thereby re
stricting its movement. The driving spring guide retainer is shouldered on its
rearward end and in turn is inserted into the recoil buffer body, and retained
in its forward movement by means of this shoulder.
c. The shock from the operating rod during recoil is absorbed by the recoil huf ..
fer through its inner and outer recoil buffer springs which are guided and
retained within the recoil buffer body by means of the recoil buffer spring
guide retainer, recoil buffer spring retainer. and recoil buffer retainer nut.
The recoil buffer retainer nut is secured by threading it onto an external
diameter of the reco1l buffer body and prevented from loosening itself by a
detent on the rear end of the recoil buffer latch spring See Fig. 1. Page 5.
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1.1. FEEDING MECHANISM GROUP
a. The feeding mechanism group parts are housed in, and mounted on, the cover.
The cover is formed sheet metal, channel-shaped in appearance, with a hinged
feed frame riveted on the front end and a spring loaded latch on the rear
end. There are various studs secured to the inside of the cover, about which
the various feeding mechanism parts operate. See Fig. 2 and Fig. 3, Pages
7 and 8.
b. The entire feeding motion is a reciprocating action, developed through the
movement of the operating rod against the feed mechanism cam. This motion is
transferred through the feed mechanism link to the feed mechanism feeding
fingers, thereby causing them to move with a reciprocating motion. This
motion causes the cartridge belt to advance across the feed plate, one cart
ridge space. with each cycle of the bolt.
c. The cartridge belt is guided. as it advances from left to right with each
cycle of the bolt, across the feed plate, thereby positioning the cartridge
in a fitted opening in the feed plate. The cartridge is held against the
opening by spring loaded shell guides with sufficient pressure to permit the
bolt in its forward progress to launch the cartridge from the belt and cham
ber it.
d The shell guides are hinged into the feed frame, which is riveted securely
to the cover, and serve a dual purpose. They apply pressure to the cartridge
and give direction to the cartridge as it is being launched from the car
tridge belt by the bolt
e. A spring loaded link retainer is hinged to the feed frame to hold the next to
last link in a belt in position and prevent it from moving into the car
tridge ramp on the feed plate.
12 TRIGGER MECHANISM GROUP
a. The trigger housing is formed steel, machined.
b. The trigger grip is made from sheet metal stampings, gas welded together. To
this assembly the trigger housing is spot welded then machined and then the
grip is rubber coated.
c The unit houses the sear, safety latch and trigger. The sear protruding
through the receiver body acts against the underneath side of the operating
rod and controls the firing cycles.
d. The trigger housing is mounted to the receiver housing by interlocking
flanges and one holding pin These, in turn, are secured by a spring lock.
13 . BARREL AND BARREL LOCK GROUP
a. The barrel is a replaceable unit and is retained in place by the barrel lock
pin. This locking device has to be turned one hundred and fifty (150°) de
grees so that the barrel can be readily withdrawn. See Fig. 3, Page 8.
b. Mounted on, and withdrawn with the barrel, are the bolt locking cams, gas
cylinder, bipod, flash suppressor and the front sight.
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