Bellona Military Vehicle Prints Series 22

ABOVE, View of soft plate 155mm Gun Mot or Carriage T.6 as originally manufactured taken o n 4th February 1942. This vehicle had the early Medium M .3 type ve rtic a l vo lute suspension and a hydrauli cal y o perated rec oil spade. Both dri ver and c o-dri ver had side doors os well as top hatches . Head lamps we re mounted on the front tra ck guards and there was no stowa ge of equipment. (U.S. offici a l photo) COVER ILLUSTRATION - DRAWN BY GEORGE BRADFORD . The United States 155mm Gun Motor Corriage M.1 2 consisted of the obsolete First World War 155mm Gun M .1918 mounted on the Main chassis components of the Medium M .3 tank as l;l carriage. Whils t only a rel ati vely sma ll quan tity of these vehicles we re built and saw acti on, they were the thin end of the wedg e in getting heavy Self-propelled Guns accepted by the U.S . Army. 155mm GUN MOTOR CARRIAGE T 6 AND M 12. - 1941/44

SERIES 22, No .85!86(US)

Dra wing s and historical reseorch by D . P. Dyer. The French 155mm gun Grande Puissonce Fi Iiou x, (Grecit Powe r Fi Iloux) named ofter it 's designer Coptai n Filloux, was used by the U .S. Artill ery in the World War I . . They found it to be the be st type of heavy field art; Ile ry de veloped and used up until then because of it's simp lici ty , wide traverse, eff ecient re coil system, long range , and durab il ity . These gun s of French manufacture were designated M.1917 by the U.S. Army . Production of 0 slightly modifi ed versio n of thi s gun took pla ce in America and was de signated M. 1918 MI . Towards the end of the first World Wor and foll owing the French adaption of ten ton Renault tractors as se lf­ propelled mounts for the GPF, the U.S. produc ed the Motor Carriog e Mk .IJ. This wos a spe c ia l Halt d esigned chassis mounting the 155mm gun, and ten we re produced. They wer e never used in acti on .

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the suggestion of the Chief of Field Arti lIery Immediately after the Armistice the U.S . Chief of Staff , appointed a board of Officers to make a study of the ~Ysuitable ca libres, types of ammuniti on, and fo rms of transport for the ar tillery assigned to the fi eld Army. This board was headed by Brigadier General Westervelt, and become known variously as the 'Westervelt Board' or the 'Cal iber Boord' . A penetrating sur vey was made and the rep ort concluded that every item of the hardware of war used by the U .S .Army requ ired improvement. Amongst it's recommendations for artillery transport the Board advocated immediate moto risation of all weapons larger than the 75mm gun and the 4" howitzer . In their summary, the 155mm gun was required to have a spe ed of six miles per hour if tracked or twelve miles per hour if wheeled. Fulfilment of the 'Caliber Board' recommendations for motorisation fell far short of the goal and the mot or­ isation of artillery soon came to be a con'troversia I matter . In the years immediately fol.lowing the 'Caliber

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ABO VE: Prior to dispatch ov erseas se venty-four 155mm Gun Motor Carriages were ov erha u led to include va rious improvements that had been incorporated mean while d uri ng produc tion of the Medium Tanks on whi ch they were based. The above photo shows on e such ve hic le afte r fi tting of sand shields. The it em, behind the ha nd wi nc h for raising the spade , is a loa din g troy for handling shel ls . (U . S. of fi cial photo)

Board' report the O rdnance Depor tment undertook a serie s of dev elo pment pr o jects fo r Self-propell ed mounts ,

but in eac h ca se work was halted either by lac k of fin an ce, loc k of inte rest on th e part of the Field Artillery,

or bo th . As late a s 1938 be tween forty a nd six ty perc ent of the Army's arti ll e ry was sti ll ho rse drawn. A

good many a rtill e rymen con te nde d tha t horse d raf t was more sa tisfactory than mach ine . Horse s nei ther ran

out of pe trol, nor required rep a irs and spore ports. If the Field Art l l le ry d id not wa nt Self-prope lled guns the

Ordna nce Departme nt cou ld nat foist the m upon the users even ha d they suffi cient fun ds to dev e lop them .

Towi ng by tr ac to rs was re la tiv el y accepta b le to the Fie ld Arti llery. Horses could al wa ys b e subs titu ted .

Until 1925 , wh en deve lopm ent work wa s aba ndoned , the 155mm gun was test ed On o n improved Holt Tra c tor

type chass is des ignat ed Moto r Ca rri ag e Mk lX whic h appea red in 1920 , a nd a lso On va rious Chri stie Conver t­

a ble mounts of wh ic h fo ur were bui It ,

O ver the fol lowing six tee n yea rs th e Ordnance Dep or tmen t did thei r be st to interest the user a rms in Self­

propelled Arti llery , bu t the Army G round Force was adamant th at towed a rti llery was more manoueverabl e ,

less co nspicuous , less Iike ly to be out of actio n for repa ir , a nd less exp en siv e .

With the a vailability of res earc h funds a s America sta rt ed her massiv e re -arma ment o rog rom, studies we re mad e by Ordnanc e tec hnical staff int o the possib i lity of mounting th e 155 mm gun M .191B MJ f rom the Mot or Ca rriage Mk .1I onto 0 carriage c onsist ing of the prin cipl e co mpone nts of th e then new Med ium Tank M . 3 . Approval fo r the man ufac ture of a pi lot model to be d esignated 155mm Gu n Motor Carri age T.6 was obtained in June 1941 . Work commen ced on th is at Roc k Island Arsenal the fo l lowing month, the comp leted pi 101' be ing del ivered to Aberd een Proving Ground, Mar yla nd, for te stin g in the middle of February 1942 . The lower huH and suspension of th is vehic le was th e some as used an the Medium M . 3 tank with return rollers mounted centrall y abo ve the bog ies . The engine was moved fo rwa rd to the spac e normal ly occ upied by, the fighting compartment of the M . 3 , an d a shortened transmis sion shaft co nnec te d thi s to th e standard gearbox and fin al dri ve. The dri ve r a nd co - driv e r sat e ithe r side of the ge arb ox and we re provid ed with Medium M.3 type visio n ports fitted wi th pr ote c tosc opes for forwa rd vision. Both ha d entry hatch es OVer thei r heads, and both als o had a sid e doar. Fue l to nks we re located in the spo nsons eith er side of the en gine . The gun its e lf wa s maunted be hind th e engi ne. At th e ex t reme rear of the veh icle was a recoil spa de whic h wa s ra ised a nd lower ed by hydrau lie ra ms. Cer ta in mechanicol de fec ts we re revea led duri ng test ing main ly with regard to the hydrau li c mechanism

of th e recoi I spa de which we re seriou s en ough to nec essi ta te comp le te red esign . Autho ri ty was req uested for

pe rmissio n to pro ceed wi th the immedia te produc ti on of fift y veh ic les pri or to sta ndar disa t io n, but thi s was

wi th he ld pe nding Ser vic e Boa rd tes ts . The T . 6 r fi tted wi th a modified rec o il spad e , was shipp ed to th e

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Fiel d Arti Ile ry Boo rd a t Fort Bragg towards the end of May 1942.

The Field Arti IIery Board were very p leased wi th the T.6 re port ing tha t it was superior in ~ b i lily an d man oeu verob i lity to other w ea pons of a simi la r calib re . For exa mp le a ta ctic al te st of mav in he gu n from fir ing position to firing posi t io n over a dista nce of six mi les took thirty -f ive minutes w it h the T. aga inst three hours for movin g the some gu n on a wheeled mount towed by a tractor . St a nda rd isation of the T. 6 as th e M .1 2 was app roved a t th e en d of August 1942. In the in te rim it a ppears that produ ct ion of these vehic les ha d a lread y co mmenced at th e Pressed Stee l Ca r Co . , no offi c ia l a uthori ty for t his ac tio n has bee n tra c ed . The fi rst se ries ve hic le come off the production line in September, 50 bei ng co mple te d by N ovember, and a further 50 by Ma rch 1943. It c ou ld be that O rdnanc e Depar tmen t, knowing of the opposi tio n by c ertai n Army Grou nd Forc e Gene ra ls to the who le co nce pt had deci ded to fo rce th e ir hands wit h a fa it a ccompl i. On the ot he r hand it may ha ve been a ge nuine erro r by the manufa c tur ing c oncern, on inc orr e ct re port, or even documents that we nt astray . What ever t he truth , the impr essi on one gains the reafter is tha t whi1st th e Army Grou nd Forc es had been fo rced to a ccep t the M . 12 th ey tried to d e lay using them for as long as possible . A few were put on ex te nded tests , but the ma jority we re o nly used for tra ining Or kept in storag e for over a yea r. Towa rds the end of 1943 repo rts had ar rived from ov ersea s re gard ing th e use (by bo th the Russia ns a nd G ermans) of big guns to fi re po int b lank at defe nsive positio ns , impe ll ed th e Armoured Boord to rec ommend immediate pro duc tio n of gun moto r carri ag es for medium and he avy ar t i llery . Eve n th e n, wit h the mass of ev idenc e in favou r of hea vy guns be ing se lf -prope lled th e Army Ground Forces di sa pproved of the rec ommendations per ta ining to th em, stating tha t the existi ng M .1 2's wou ld mee t all a nti c ipated req uirements fo r 1944. By February 1944 , every c ha nge and modifica tio n having been fina lised for the M. 12 au thority was given for Ba ldwin Loc omoti ve to reb uild sev enty- five veh ic les . This ga ve suffi c ie nt ve hicles to equ ip six Battalions ea c h cons ist ing of three Ba tteri es of four guns wi th thr ee spare. Reb uilding of seven ty- fou r ve hicles was co mp leted by May 1944 an d by the e nd of J uly 1944 shipm ent to the ba ttle fronts overseas hod be en effec ted. The M . 12 differ ed from the pi lo t T. 6 very littl e . The main diff er en ces be ing the la ter type of ve rtica l vo lut e spri ng suspens io n fitt ed w it h the tra iling re turn ro ll ers, A rud imentary gun shie ld for the gun layer, an d a winch ope ra ted reco i l spade. Te n she lls tog ether with c ha rges and fu ses we re ca rried . The she l ls w ere a ccomodat ed ve rtic a l ly in rec essess in th e flo or of the gun comportm ent . Two cha rge s we re secu red ce ntra lly behind the gun , the remainder of th e c ha rges bei ng located in rac ks be ne a th th e two gun cr ew members se ats a t the rear of th e left ha nd sponson . A furt he r two gun crew membe rs were provided with se ats formed from the rise r of th e bottom step fi tt ed between t he a rms of the recoi I spad e . On the unde rside of t his seat the BELOW: This photo shows an othe r view of the re buil t ve hic le on pa ge 4 . Stow age in this phot o is not co rrect The c rowbar shoul d be loc a ted on the insid e fac e of the left ha nd fu e ! ta nk above the engin e co mpa rtment, and the star ter han dl e is lyin g with the pion e er too ls inst ead of in it 's bracket On th e right hand sponson wa l l. (U.S . offi c i 01 phot o)

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ABOVE: The above photo taken at the Field Arti Ilery Board test area at Fort Bragg in March 1943 shows a standard M.12 with the recoil spode lowered . Of interest is the correct stowage position of the galvani sed bucket between the twa spade seats, and the webbing "safety belts" for the occupants of these seats. (Official U.S. Photo.) BELOW: Although the tarpaulin is not pre sent t the strops for retaining sa me under the spade seat show on this view of the thirty-fifth M.12 produced . This vehic le is in travelling order . A point of interest is that the height of armour plate around the seals at the rear of the left hand sponson had not yet been increased at this time. (U.S. offi cial photo)

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vehicle tarpaul in was stawed, and the footrest wa s formed fram the lid of a carbine box. The spade was rai sed by means of a hand operated winch on the right hand fuel tonk cover, and retained in position by a tie rod each sid e . Folding choc ks were carried an the R.H. front track guard and used to stop the vehicle movi ng forward on c ounter rec oi I. The rea son for the brackets a tt ac hed to the rear bogies is obscure. Some photographs appear to show w edg es

driven in be twe e n this and the trac k and it is suggested that they might be to sto p the track jumping off the

return rollers when the gun was fired. It cou ld be that they were to relieve she er st resses on the rear bogie, or act as supp orts for the sponsons.

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One of the items requ ested during the rebui Iding were sand shie lds ot he rwise there were no noticeable

differences . A canvas co ver was d esigned to fit over the gun compartment to protect the c rew in inclement

weat he r , but it is not thought that thi s ever become standard issue, in view of the fact that shou ld a leak

occ ur in the exhaust system it would be extremel y dangerous For the gun crew.

Considering the obso le te type of gun utilis ed, M.12's proved th e advantages of the heavy Self-propelled gun .

It' s lif e howe ver Was very limited. The T.83 which utilis ed the for more modern 155mm gun M .2 on a wider

and long er chas sis wi th Horizontal Volute Spring Suspension and 23" trac ks started comi ng off the production

line in Febr uary 1945 and standardised in Moy 1945 as the MAO. At the same time the M .12 was reclassified

as Limited Standard, being declared obso le te in August 1945. It is of interest to note that from the time the

pil at was rec ommended the T.83 too k exac tly one year to sta nda rdisa t ion being approved .

The onl y known rema ining example of the M.12 is retained at Aberd een Proving Gr ound, Moryland.

The main se ries of scale drawings, by Phil Dyer , are the result of se ver al y ea rs work a nd research whic h

includes deta iled measuring of the onl y vehicle sti ll in exis ta nc e at the Abe rdeen Proving Grou nd. These

dr awings and the historical data whic h have been comp iled so ca ref ull y by Phil Dyer and his many America n

friends a re the most ac curate possib le w ith the material exi sts to-d oy . ...Ed.

BELOW: These two phot ographs co mpare the rea r view of the M.12 with spade lowered with the Cargo

Carrier T.14 p i lot a lso with tailgate lowered . The M.12 shown is on early vehic le in vie w of there being

a st ep down directl y beh ind the gun mount where the looding platform was on the T.6 originall y.

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Exc e rpt from a Batt Ie Gr o und rep ort o n the M. 12 "Bottle of Se ig rie d Line" - bottl e of movement ended temporaril y whe n th e U. S . First Army re ached the German bard er . The bat tle of the Sieg fried line be gan. Duri ng this bo ttl e the battali o n hod a d ual role: as on Artill e ry ba tt a lio n del iveri ng supporti ng fir e , and as a si ege gun redu cing pillboxe s and other fixed fo rti f ic a tio ns in th e ar ea . It is not possi bl e at this tim e to gi ve a detai led te chnic a l acc oun t of the use of the M . 12 as a siege gun. Most of th e pi Ilbaxes destroye d or neu t ra lise d by the battali on are sf II an the other side of the fro nt lin es . Some ge ne ra l obse rva ti ons ca n be mod e even now , however . When the mo bil e phose of the campaign e nded with the in vestmen t of th e Si egf rie d Line 'B' battery was det ac hed from th e battal ion a nd attached to th e 9 th Infan try Division for the spec ifi c purp ose of dire ct fir e against pillbox missio ns in addition to it's re gular ar ti lle ry work for th e 3rd Armoured Division . From 15th to 24th Sep temb er . , thi rty-fi ve direct f ire missions we re assigned to the battalion . O f these twe nty - ei ght were pi llboxes and seven we re forti fi ed house s o r observa t ion pos ts. Si xteen of th ese missions were compl etel y suc cessfu l. O n eac h of these missions c omp le te destructi on of the pi l lbox, penetra tio n , or di re ct surr en der to th e fi re of the M .1 2 wa s acc omplished . On t he remai ning ninet e en missions vary ing degrees of neutrali sat ion we re ac hieved. In most of these latter c ases it has be e n possibl e to oc cu py the pillbox es or oth e r struc tures on whic h the fi re was d eli vered , but from pri son e r of war repor ts i t is co nc luded th at ca sual ti es d ue to c oncussion a nd chipp ing of concret e occurred in all cases . An overa ge of te n ro unds we re fi red on eac h mission . Ba sed On the exp eri enc es so for ga ined we be liv e tha t th e M .12 sui ta b ly empl oyed , wi ll d estroy , pen et rat e, or knock-out of a ction pillboxes of the S iegfr ied Line type . The projectil e prod uc es cas ua lt ies and lowe rs mo rale of the pill box occ upants . No penet ration of the heavy 14 " ste el c upo la s whic h th e be tter typ e pi Ilbaxes ha ve ar e known of. It is a lso d iffi cu lt to pen etra te the best type of co nc re te , but in some cases seven fee t of co nc re te we re pe netra ted fa irl y easi Iy. The opt imum range for th e p i Ilbox work wou Id app ear to be between 1000 o nd 2000 yards . At thi s range th ere is very li tti e loss of accu racy or muzzl e ve loc ity , and the Crew a re out of rang e of muc h of th e enemy's sma ll arms fire . Pill box a tt acks shou ld be c lose ly co - ord inated wi th th e suppo rt ing infan try an d tan ks so th at neutralising fir e ma y be de liv ered on the pillboxes whi le the M .1 2 is shoot ing for destr uc t ion Most of the missio ns we re fi red by indivi dua l p ieces , but perh ap s massing the simultan eous fir e of several M. 12' s wou ld gr eatl y in creas e the con c ussion e ffec t as we ll a s the sha tteri ng a nd p en e trati on of th e co nc re te, thus c onservi ng ammu niti o n . Rood mar ches of 200 mil es ha ve been ac c omp lished in on e day an d the ful l tra c k carriag es ha s a lso mode possibl e crass cou ntry mob ility BELOW: Preparing on M .l? for acti on towards the en d of the war in G ermany. The battery was bei ng ernp lcc ed for long ran ge fir ing , a s insta nced by most of the gun c rew no t bo thering to wear their helmets. In th e fore­ ground o ne shell is show n in the loadi ng tray , furt he r she lls are lay ed o ut on a ta rpa ulin to ke ep them c lea n . The c rew member to the left is shown ca rryi ng twa of Ihe-r an ging rods use d in posit ionin g th e gun.

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155mm Gun Motor Carriage M 12. Scale 1 :48(a"tol' 0").

Armament

Technical Specification for 155 mm Gun Motor Carriage M 12. Seating: Driver, co-driver and 4 members of gun crew. Weight, Combat loaded: 58,770 lbs , 26.24 Long tons. 29.4 Short tons. 26.65 Tonnes. Performance

20 m.p h, (32 Km.p.h.)

Speed, Max. Road: 22 degrees (40%)

Max. Gradient: 3' 0" (91.4 cm)

Fording depth: Trench crossing: 6' 0" (182.9 em)

l' 6" (45.7cm)

Step: Ground pressure: 12.6 Ibs/sq.ins (0.88 Kg/sq.cm)

Range {internaI fuel) Road: 190 Miles (306 Km)

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Dimensions

22' 0" (670 em)

Length overall: Width overall: 8' 10" (269 ern)

Height:(To top shield raised) 8 1 1 0 " (269 em)

Ground clearance: l' 5" (43.2 cm)

7" 2" (218 em)

Fire height of gun: Road wheel dia (overall)l' 8" (50.8 em)

Main: 155 mm M 1917 Al

Calibre, and length in calibres: 155 mm/cm (6.102 ins) V38

Traverse: 14 degrees R 14 degrees L. Operation: Hand.

Elevation: plus 30 degrees, minus 3 degrees.

Rate of fire: 4 rounds per minute.

Max. Range: approx: 20,000 yards. Muzzle velocity 2,400

approx: Projectile weight: HE 94 Ibs, AP 100 Ibs, smoke 123 Ibs. Stowage Ammunition, separate loading: Internal Fuel capacity:

10 rds , 166.6 Imp gals. 200 U.S. gals. 757 Litres. 80 Octane minimum

Armour Hull, Drivers plate: Sides, upper: Decking: Engine covers: Gun shield:

1" (25.4 mm)

(12.7 rnm) at 0 degrees.

3/8" (9.4 mm) at 90 degrees.

3/8" (9.4 mrn) at 90 degrees.

!" (12.7 mm)

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Trackwork

Centres: 7' 0" Length on ground: 12' 8" Width: l' 4" Pitch: 6" Number of links per track: Type: Rubber

(213 em)

(386 em)

(40.6 em)

(15.2 em)

79.

Block Double Pin.

Transmission: Steering: Suspension:

Continental R-975C-1 400 HP 9 cylinder

air cooled petrol. Synchromesh SF IR Controlled differential Vertical volute spring.

Length overall: Height to MG ring: Ground clearance:

19' 10"(604 em) 9' 4"(284 cm) l' 7"(48cm)

Armament Main: Ammunition:

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M30.

Crew: 2 Weight, Combat loaded: 45,580 Lbs. 20.3 Long tons 22.8 Short tons. 20.5 tonnes. Dimensions

Mechanical Detai Is

Engine:

Technical specification variation for Cargo Carrier

1 x .50 ca 1M2. HB. 1000 rds of .50 calibre.

Drawings of the M 12 family of vehicles,

reproduced here at 1 :48 scale{*" to l' Oil).

From top to bottom:

Section view of the T 6 - note the complex

recoi I spade mechanism.

Side view of the Cargo Carrier M 30.

Side view of the 155mm Gun Motor Carriage

M12

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CARGO CARRIER T 14.AND M 30 . - 1942/44

S ERI ES 22, No. 87(US)

Drawing and historical research by D.P.Dyer. ..

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In March 1942 after:r e'c eipt of the Pilot T.6 it was reali sed that th e amount of ammunit ion that could be carried in th is vehi cle would se verel y restr ict it's operation . A project was therefore initiated by the O rdnanc e Department for the devel opment of a compa nion vehicle based on the chassi s of the T.6 This vehic le was to corry additional ammun ition and was to service th e gun motor carriage. This was de signated T. 14. The Field Art i Ilery Board reco mmended this de velopment in Ju ly 1942 (a t the sa me time as they recommended adoption of the T.6) and authority was grant ed for procurem ent of fif ty. Mi litary char acter isti cs were approved in August and the soft plate pil ot model T . 14, to ge the r with a produ ction M,12 had stowage a rra ngements decided upon at Erie Pro vin g Ground by rep rese ntcflve s of the Armored Farce and Field Artillery Board 'e arl y in September. 38 had been co mple ted by early No vember . In view of production ha ving c ommenced prior to study of the pil ot model a lot of co nfusio n oc c ured wi th regard to modifications requested a nd it is not known ex a c tly how many T.14's were produced or whe n the y were completed. A recommendati on fo~ standardi sa tion of the T. 14 as Cargo Carrier M.30 Was mad e in Se ptember but ne ver appears to ha ve been approved although the Or dnance Dep ortm ent from then on a lwa ys refered to it as the M.30. Rebuilding of seventy-fi ve of the se Cargo Carri ers took place at the some time as the rebuild ing of the M .12's an d they we re shipped ove rseas at the sa me time on the basi s of on e cargo c ar rier to each G un Motor Carriage . Auromctlvell y the same vehic le as the gun ca rriag e the Cargo Carri ers differed in having stow age for faurty shells in plac e of the gun mount. A compartment to th e rear of the right ha nd fuel ton k contained nine propelli ng c ha rges , t e n were sto wed in the centre of the ve hic le behind the she l ls , and a further twen ty-one in a comportme nt behind the left hand f uel tank. The rear of the ve hic le was fo rmed by a ta ilgate whi ch wh en lowered formed ste ps for ent ry into the vehic le for loading and unloa ding. With the tai lga te ra ised the riser for the bot tom ste p (with the addit ion of c ushio ns) formed sea ts for thr ee gu n c rew members. A fur ther two seats were loca ted at the re ar of the spo nsons in line with the tailgate seats . The c argo comportm ent was surmounted by a ring mount for a .50 cal mach in e gun for anti-ai rc raf t an d loca l defence. As a point of interest the we ight of 155mm ammunition c arri ed totaled 2 .25 10ng tons(2 .5 sho rt tons) The M , 30 was dec lored obso let e a t the same time as the M . 12 a nd none ar e tho ught to be sf II in existence. BELOW, This ve hic le was the pilot Cargo Carrie r T ,14. Being converted di rec tly from the T.6 which had the sa me War Departmen"t Numb er 30705 3 . It retai ned the rear track guards wi th a step up to the sponson extension s . The ties to th e rear bogies we re not tapered , and he adli ghts we re mounted on the front track guards. Front a l v iews of the sa me ve hicl e also show brackets for the gun rrove llng lock fitt ed to the dri vers front p lat e (U.S . offic ial photo )

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These two views show a productio n Cargo Car rie r T.14 wit h the tailgate lowe red. The .50 co l machine gun on the rin g mount is enclosed in it's pro tec tiv e wa terproo f cover . The brocket on the ri ght rear propellant ch arge compa rt ment cover wou Id appea r to be for a spare .50 c a l mach ine gu n barr el . Grousers were conta ine d in the two box es On the fuel tan ks, and, as a n the M. 12 the se boxes were sometimes fitted with lids . (U ,5 . offi cia l photos)

ABOVE: In t his view of T.1 4 numbe r 29 (U. S . 4080932) shown in travel ling or der it wil l be noted tha t the

dr ivers hood is in the ra ise d positi on. This hoo d consisted of a fo lding canvos cov er with 0 tra nspare nt

win dshie ld fit ted wit h a wi ndsc re en wiper. It was fitted over the drivers ope ned tap ha tc h for use whe n he

was dri ving the vehic le wi th h is sea t in the raised position .

BELO W: A ba ttery of M . 12's, fitted ou t for deep wading , comi ng ashore during the Normandy landi ngs.

It is inte resti ng to see the wa y the de ep wading screens hove bee n fit ted . Note the e xtend ed exha ust pipes

on the sides. (I. W. M . Photo)

15

ABO VE; Unfortunatel y good quali ty phot ograph s of t he I S U series of Assault Guns a re not readil y

ava i lab le , however, the photograph used here ill ustrates the gene ral lay out of on e of the units fitted with

the some gun as the IS I an d II ta nks. This mod el was known as the r S U 122 0- 25S .

SOVIET

ISU - 122 GUN MOTO R CARRIAGE.

- 1944/45

SERIES 22, No .88/ 89 (SU) •

Histor icol reseorch by J. F. Mil som. Drawings by K. M. Jones. During 1943 the Soviet High Comma nd insti gated a progr amme for the producti on of a se ries of se lf-propelled a rti llery pi e ces ba sed on curren t Red Army ta nk c hossis , In the hea vy cl a ss, two weap ons we re to be mounted on the KV c hass is; thes e consisted of th e 152mm M-1937/43 (ML-20 S) co rps howi tzer and the 122mm gun M-1944 (D- 25S). Aft er unsucces sful a ttempts to mount th ese weapons in the o ld KV- II turret , more . sa tisfac tory so lutio ns were ach ie ved with ca semate mountings. These becom e de signated SU- 152 a nd SU- 122 respecti vel y . The 5U-122 consiste d of the Mod e l 1931-37 122mm gun mounted on a mod if ied KV ch assis; the weapon was int ercha ngeabl e with the 152mm howit zer to form the 5U-152 . Both were sta nda rd ized during 1944 . Not long a fter produc tion was unde rway, howeve r, the 15-1 heavy tan k appeared o nd as a result newer more sa tisfac tory mountin gs for th ese weapons were de vel oped on th is c hassis . The wea pons nOW beca me t he ISU-152 and ISU-122 (D- 25S). The 15U-1 22 (D- 25S) was e nco unt ere d by the Germans towar ds th e end of World War II whe re it be came designated er one ously a s the SU-249 . SU- 249 was a factory number a nd not the nomenc la ture by whi ch the ve h ic le was gen erall y known in the Sov iet Army. Aft er a short whi le produ c­ tion of the 15U-1 22 with the 0 -255 gun wos discontinued and further vehic les recei ved the modif ied 122mm co rps gun M-1 93 1/37 (A- 19) and we re c orrespondin g ly de sign a ted ISU- 122 (A-1 9S) . This second ve hic le has al so been referred to as the 15U-122A a nd by the Hungarions, who wer e issued with se ver al, as the 15Z-122 . The ISU-122 (0 -255) is believed to ha ve been produc ed either as a stop-gap mea sure to prov ide weapons to fi e ld units dur ing World Wa r II a t a time whe n the Sov ie t Army was short of a suitab le heavy assa ult gun, or it may ha ve been formed a s a result of th e unbal anc ed producti on of compone nt tank por ts . The 15U- 1225 we re produc ed up to the end of World Wa r II whe n produc ti on is believed to ha ve ceased . The 15U-122 (A- 195) c onsist ed of a modified 122mm corps gun M-1931/37 (A- 19) mount ed in a fixed super­ st ructure on the IS-l or II chossis. The ISU-1 22 (d- 25S) was identical to ISU-12 2 (A- J9S) except for the gun an d mont Iet. The gun, a 122mm M-1943 (D-25), was the some as tha t used on the IS se ries of he avy tanks . Distinguishing features were its th in ne r bar rel and double-baffl e muzzl e-broke . The mantlet wa s smaller and more round ed that that of the ISU-122 (A- J9S) . The supe rsturct ure consisted of a full y-encl osed comportmen t mounted on the front half of the c ha ssis . The front of the superstructure was set slightl y back from the front of the hull. It consisted of a single piece , s lop ing plate, with a massive, two-piec e mantlet mounted on the right-hand side . The montlel was co vered by a shield which was hin ged to the right front of the roo f. Each s ide of th e supe rstr ucture tap ered sli ghtly to the front an d rea r and consited of two unequal siz e ar mour plates we lded together with a ve rtica l seam .

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The re a r pla te was vert ica l a nd con ta i ned a re c rc nqu lor access doo r an the ex tre me le fr, This hatc h cou ld be opened, e ithe r in dep endentl y or in co n junc tion wit h on adj ac e nt hatch o n the roof , to fo rm a sing le la rge en t ra nce to th e ve hic le . The roof was f lat an d contained two rou nd hatch es ne a r the front , in additi on to the rec ta ngu la r ha tc h at the left re ar. The hull was th e same as tha t of th e 15- 1 hea vy tank. The rea r deck wa s fl at a nd had a sing le rai sed en gine compartm ent ve nt ext endi ng across th e en tire width . The rear plate was broad , had a prom in ent shope a nd e xten d ed aCrOSS t he e ntir e wi dt h of the ch assis . Mudgu ards ex tended forward , be yond the c hossis , at the fron t of th e vehic le . The suspe nsion system WaS the tors io n-ba r type id enti cal to that of th e IS tanks , co nsist ing of 6 indi vidu all y­ sprung doub le road whee ls thr e e do ub le tra ck-support ro lle rs, a nd a rea r dri ve spro c ket on each side . The to rsio n bars exte nded th e full wid th of th e ve hic le . The singl e -p in st ee l t ra c k was approxim atel y 26 in c hes wide . . The a rmour va ried co nsiderab ly in thickness on both the superstruc ture and th e hull . Ro lled a rmour plate was used ex te nsi ve ly on the superstruc ture , and the hu fl was mad e of sha ped castings . Armour thickness , whic h was greatest o n the front , va ried from J90mm on th e mantl e t to 90mm o n the front of th e super struc ture. The sides of the supe rstruc tur e a nd th e hu II were 60-90mm thi c k whereas the reor deck a nd the roof of th e supe rstructure aver aged 25mm th ic kness , The e ngi ne was the same as t hat used in the ea rly IS ta nks and co nsisted of the rear-mounted V- type 12 cy linder di esel whic h de ve lope d 5 12-550 HP at 2,000 rpm. The engine was wat e r- co o led and hod a pres sure-type lub rica ti o n syste m. The fue l capacity has be en est imored to be 66-1 06 ga lls of diese l fuel c ont ai ned in the ma in ta nks, eac h of four cy lind ric a lly sha pe d oux i l licry ta nks wh ic h may be ca rried on the re ar dec k, a nd ea ch of two sma lle r c y lindrica l ronks wh ic h were some t imes carried on the rear p la te . An additiona l ta nk could be carr ied be hin d the supers tructure. The armame nt of bo th mod els cons isted of 0 122mm gu n a nd a 12. 7mm AAMG . The mai n g un , use d on th e ISU-1 22 (A- 19S) was the 122mm M- 1931/44 (A-19S) which was ba ll isti c a lly tlce some as the sta ndard Sov ie t 122mm co rps M- 193 1/37 (A- 19) from whic h i;- hod be en adop ted . This gun hod a reinforcing ba nd o n th e end of th e barre l . The main gun used On rhe IS U-1 22 (D-25S) Was th e 122mm M- 1931/44 (D-25S) wh ich had the some ba ll ist ic cha ra cter isti cs os the 122mm to nk gun M- 1943 (D- 25) used o n all th e IS se ri es of heavy ta nks a nd had a doub le­ baf f le muaz le-broke . Both we a pons fir ed sepa ra t e loadi ng a mmunt io n and hod a ra nge of approx imatel y 16 ,000 yar d• . The ISU-1 22 (D-25S) had a high e r ra te of fir e , 5-6 rou nds per minu te, whe re as the ISU-122 (A- 19S) fired on ly 3 rou nds per minute . The A- 19S fi red s lowe r be cause i t hod a sc rew type bre ach-b lock whereas th e D- 25S had a slid ing-wed ge type brea c h-b lock . A 12 . 7 mm dua l- pur pose machi ne-gun (DsHK) was pe des ta l- mounte d forwa rd of th e righ t- hand hatch on the superstruc tu re roof of both ve hi c les . In add ition two trip od mounts we re ca rried and two mac hin e-c a rbin es , a . we ll as 25 han d-gren ad es . BELO W: The mo re re gu la r ve rsion of th e IS U 122 wi th th e A-195 g un . Russian Infa ntry ride On a n IS U during t he fi na l stages af th e war on the Ea st Fron t . .-N OTE: Bello na Mi litory Ve hic le Pri nts nor mall y use d the vehic le desi gnati on in th e namenc lotu reo f th e c o unt ry of orig in on th e gro unds th a t this is the o nly correc t title . In th e cas e of Soviet ve hic le , this is not possib le due to th eir a lphabet . However , instead of the correct Russian design a tion we are u. ing the ac c epted" English " phonetic equ ivalent. Thus th e accura te de sign a tion fo r th e Jose ph Stol in tank is the IS , simi la rly th e assa u lt guns ar e the IS U . The "G er man" phonetic giv es JS a nd J SU , but if this syst em is used the KV(Klimenti Vorishi lov) must be designated as th e K W.

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23 m.p .h . (37 Km.p.h.) 10 m.p.h. (16 Km.p.h.)

32' 2 11

10' 0"

21 1 1 0 " 10 1 2"

Centres: Nt length on ground: Q Width:

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(236. 5 em)

(56 ern)

(252 em) (45.7 em) (181 em)

(356 cm) (305 em)

(980 em) (680.5 em)

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(426 cm) 14' 8" 2' 1.5/8 11 (65.2 ern)

7' 9"

Height: 1 w/o AAMG 8 1 3" Ground clearance: l' 6" 5' 11" Fire height of gun: Turret ring dia: None Road wheel dia (overall) 1 1 1 0 "

length overa II: length: w/o gun Width overall: Width over tracks:

12.7mm DshK AAMG anti -ai rcraft mounti ng.

M1938/46.

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Type: Cast and rolled homogeneous. Hull, Nose upper: 4.331 "(1lOmm)at 30 degrees Nose lower: 5.000"(J27mm) at 70 degrees Glasis plate 2. 953/1( 75mm) at 74 degrees

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1 x 9-R transceiver. TPU-3 laryngaphone. 5 periscopes.

3.543"( 9Omm) at 30 degrees 2.362 t02. 953/1(60 to 75mm) at 15 degrees 2. 165"( 55mm} at 0 degrees 1 . 181"( 30mm) at 90 degrees 7.480"(19Omm) rounded

15 degrees 0 degrees 50 degrees 90 degrees 90 degrees

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Crew: 4

Weight: Combat loaded: 101,400 Lhs.

Length overall: 33 11 0 11(1006 ern) He ight: w/o AAMG 8' 2/1( 250 ern)

Mantel:

Armour

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3.937"(100 mm}rounded.

Main: 122mm assault gun M1944 (D-255) Calibre, and length in calibres: 122mm(4.803 inches} , 43 calibres long. Traverse: 14 degrees (total) Operation: manual. Elevation: plus 16 degrees, minus 3 degre~ Tsh 17 telescope sight and diat sight. Sights:

Armament

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Technical Specification variation for ISU-122(D-25S}.

Observation:

Communications:

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on optional

122mm assault gun M1931/44 (A-19S) 122 mm(4.803 inches) , 46 calibres long. 11 degrees(total). Operation: Manual. plus 19 degrees, minus 3.5 degrees ST-18 telescopic sight and dial sight of M31/37 field gun.

Synchromesh 4-fwd. 1. reverse plus 2 speed auxi lIiary. regenerati ve

6 twin steel wheels/side sprung on torsion bars,

3 return rollers/side.

Ammuntion, main armament: 30 rds. - 122 mm Ammuntion, secondary armament: 500 rds , - 12.7 mm Internal fuel capacity: 66 imp.gals(300 litres) or 106 imp gals (482 litres) with additional fuel tanks.

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Secondary armament:

Main: Calibre: Traverse: Elevation: Sights:

Armament

Transmission: Steering: Suspension:

Front:

Sides:

Rear;

Roof:

Mantel:

Superstructure

1 x Model V-2-IS. 38.9 litre watercooled, V12 diesel, developing 520 hp at 2100 rpm.

Engine:

Mechanical Detai Is

3.504/1( 89mm) at 2. 953/1( 75mm) at 2 .520"( 64mm} at O. 984"( 25mm) at 0.748"( 19mm) at

I S U - 122 A - 19 S . Scale 1 : 48 (£-/I to l ' 0").

Sides, upper: lower; Pear; Decking: Belly:

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(17.1 ern) Pitch: 0' 6~1I Number of links per track: 77-90. Type: cast manganese steel, dry pin.

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Max. Gradi ent: 36 degrees Fording depth: (130 em) 4 1 3" Trench Crossing: 8 1 2 11 (249 em) Step: 3 1 3 11 (100 ern) Min. Turning Circle: 31 1 2·' ( 9.3 metres)

Ground pressure: 10.41 Ibs/sq.ins

Range(internal fuel},Road: 112 miles(180Km}, 190miles (306Km)

with additionla tanks. Cross country: 52 miles (84 Km). Power to weight ratio: 12.8 HP/ton. pimensions

Speed, Max. Road: Cross Country:

Crew: 5

Weight, Combat loaded: 101,470 Lhs. 45.3 Long tons.

50.8 short tons. 46.43 tonnes. Performance

Technical Specification for ISU-122 (A-19S)

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