Dra wing s and historical reseorch by D. P. Dyer.

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2 ABOVE, View of soft plate 155mm Gun Motor Carriage T.6 as originally manufactured taken on 4th February This vehicle had the early Medium M.3 type ve rtic a l vo lute suspension and a hydrauli cal y operated rec oil spade. Both dri ver and co-driver had side doors os well as top hatches. Head lamps were mounted on the front tra ck guards and there was no stowage 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 quantity of these vehicles were built and saw action, they were the thin end of the wedge in getting heavy Self-propelled Guns accepted by the U.S. Army. 155mm GUN MOTOR CARRIAGE T 6 AND M /44 Dra wing s and historical reseorch by D. P. Dyer. SERIES 22, No.85!86(US) The French 155mm gun Grande Puissonce FiIioux, (Grecit Power 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 simplici ty, wide traverse, eff ecient recoil system, long range, and durabil ity. These guns of French manufacture were designated M.1917 by the U.S. Army. Production of 0 slightly modifi ed version of this gun took pla ce in America and was de signated M MI. Towards the end of the first World Wor and foll owing the French adaption of ten ton Renault tractors as se lfpropelled mounts for the GPF, the U.S. produced the Motor Carriog e Mk.IJ. This wos a spec ia l Halt d esigned chassis mounting the 155mm gun, and ten we re produced. They were never used in action. Immediately after the Armistice the U.S. Chief of Staff, 0;' the suggestion of the Chief of Field Arti liery appointed a board of Officers to make a study of the Ysuitable calibres, types of ammunition, and forms of transport for the ar tillery assigned to the field Army. This board was headed by Brigadier General Westervelt, and become known variously as the 'Westervelt Board' or the 'Cal iber Boord'. A penetrating survey 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 motorisation 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 orisation of artillery soon came to be a con'troversia I matter. In the years immediately fol.lowing the 'Caliber 2

3 . SPADE LOWERED REAR /,6 % ---,- "METRES o I 2 3 w 155mm GUN MOTOR CARRIE 16

4 ABOVE: Prior to dispatch ov erseas se venty-four 155mm Gun Motor Carriages were ov erha uled to include va rious improvements that had been incorporated mean while duri ng production of the Medium Tanks on whi ch they were based. The above photo shows one such ve hic le after fi tting of sand shields. The it em, behind the ha nd winc h for raising the spade, is a loa din g troy for handling shel ls. (U. S. offi cial photo) Board' report the O rdnance Deportment undertook a serie s of dev elo pment pro jects fo r Self-propelled mounts, but in each case work was halted either by lac k of fin an ce, loc k of interest on the part of the Field Artillery, or both. As late as 1938 between forty a nd six ty percent of the Army's artill ery was sti ll horse drawn. A good many a rtillerymen con te nde d tha t horse draf t was more sa tisfactory than mach ine. Horses nei ther ran out of petrol, nor required rep a irs and spore ports. If the Field Art lllery d id not wa nt Self-prope lled guns the Ordna nce Department cou ld nat foist the m upon the users even ha d they suffi cient funds to dev e lop them. Towing by trac tors was re la tiv ely acceptable to the Fie ld Arti llery. Horses could al ways be subs tituted. Until 1925, when developm ent work was aba ndoned, the 155mm gun was tested On on improved Holt Tra ctor type chassis des ignated Moto r Carri age Mk lx whic h appea red in 1920, a nd a lso On va rious Chri stie Convert able mounts of wh ic h four were bui It, O ver the following six tee n years 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 that towed arti llery was more manoueverabl e, less conspicuous, less Iike ly to be out of action for repair, a nd less expen sive. With the availability of researc h funds as America sta rted her massiv e re -arma ment orog rom, studies were mad e by Ordnance tec hnical staff int o the possib ility of mounting th e 155mm gun M.191B MJ from the Motor Ca rriage Mk.1I onto 0 carriage consist ing of the prin ciple co mponents of the then new Med ium Tank M.3. Approval fo r the man ufac ture of a pilot model to be designated 155mm Gu n Motor Carri age T.6 was obtained in June Work commenced on th is at Roc k Island Arsenal the fo llowing month, the comp leted pi 101' be ing del ivered to Aberd een Proving Ground, Maryland, for testin g in the middle of February The lower huh and suspension of th is vehic le was the 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 rward to the spac e normal ly occupied by, the fighting compartment of the M. 3, an d a shortened transmis sion shaft co nnec te d this to the standard gearbox and fin al dri ve. The dri ve r a nd co - driv er sat e ither side of the gearb ox and were provid ed with Medium M.3 type visio n ports fitted with pr otectoscopes for forwa rd vision. Both had entry hatches OVer their heads, and both also had a side doar. Fue l tonks we re located in the spo nsons either side of the engine. The gun its e lf was maunted be hind the engi ne. At th e ex treme rear of the veh icle was a recoil spa de whic h was ra ised a nd lowered by hydrau lie rams. Cer ta in mechanicol defec ts we re revealed duri ng testing main ly with regard to the hydrau li c mechanism of th e recoi I spade 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 rmission to pro ceed wi th the immedia te produc ti on of fifty veh ic les pri or to sta ndar disa tion, but thi s was wi th he ld pe nding Servic e Board tes ts. The T.6 r fitted wi th a modified reco il spade, was shipp ed to th e 4

5 Fiel d Arti Ilery Boord at Fort Bragg towards the end of May The Field Arti IIery Board were very p leased wi th the T.6 reporting tha t it was superior in b i lily an d man oeuverobi lity to other wea pons of a similar calibre. For exa mple a tactical test of mavin he gu n from fir ing position to firing posi tion over a distance of six mi les took thirty -five minutes with the T. aga inst three hours for moving the some gu n on a wheeled mount towed by a tractor. Sta nda rdisation of the T. 6 as th e M.1 2 was app roved a t the en d of August In the inte rim it a ppears that produ ct ion of these vehic les ha d a lread y co mmenced at th e Pressed Steel Ca r Co., no offi c ia l authori ty for this ac tion has bee n tra c ed. The first series ve hic le come off the production line in September, 50 bei ng co mple ted by November, and a further 50 by Ma rch It cou ld be that O rdnance Departmen t, knowing of the opposi tio n by certai n Army Grou nd Forc e Gene ra ls to the who le co ncept had deci ded to fo rce their hands with a fa it accompl i. On the ot he r hand it may ha ve been a ge nuine erro r by the manufac tur ing concern, on incorr ect report, or even documents that went astray. What ever the truth, the impr ession one gains the reafter is tha t whi1st the Army Grou nd Forc es had been fo rced to accept the M. 12 th ey tried to de 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 training Or kept in storage for over a yea r. Towards the end of 1943 repo rts had ar rived from ov ersea s regard ing the use (by bo th the Russia ns a nd G ermans) of big guns to fi re point b lank at defensive positio ns, impe lled the Armoured Boord to recommend immediate productio n of gun moto r carriag es for medium and heavy ar tillery. Even then, wit h the mass of ev idenc e in favour of hea vy guns being se lf -prope lled the Army Ground Forces di sapproved of the rec ommendations per ta ining to them, stating tha t the existi ng M.1 2's wou ld mee t all antic ipated req uirements for By February 1944, every c ha nge and modificatio n having been fina lised for the M. 12 au thority was given for Ba ldwin Locomoti ve to reb uild sev enty- five veh ic les. This gave suffi c ie nt ve hicles to equ ip six Battalions ea c h cons isting of three Ba tteri es of four guns wi th thr ee spare. Rebuilding of seven ty- fou r ve hicles was comp leted by May 1944 an d by the e nd of J uly 1944 shipment to the ba ttle fronts overseas hod be en effec ted. The M. 12 differ ed from the pilot T. 6 very littl e. The main differ en ces be ing the la ter type of ve rtica l volute spri ng suspens ion fitted with the tra iling return ro llers, A rud imentary gun shield for the gun layer, an d a winch ope ra ted reco il spade. Ten she lls tog ether with cha rges and fu ses we re ca rried. The she lls were a ccomodat ed ve rtic a lly in rec essess in the flo or of the gun comportm ent. Two cha rge s were secu red centra lly behind the gun, the remainder of the cha rges bei ng located in rac ks benea th the two gun cr ew members se ats a t the rear of the left ha nd sponson. A furthe r two gun crew members were provided with seats formed from the rise r of th e bottom step fi tted between the a rms of the recoi I spad e. On the unde rside of this seat the BELOW: This photo shows an othe r view of the rebuil t ve hic le on page 4. Stow age in this phot o is not co rrect The c rowbar should be located on the insid e fac e of the left ha nd fu e! tank above the engine co mpartment, and the star ter han dl e is lyin g with the pion e er too ls instead of in it 's bracket On the right hand sponson wa ll. (U.S. offi c i01 phot o) 5

6 ' = % I FEET :-:...J =r... Looo;;ow... iiiiiiij I I I o I METRES 155mm GUN MOTOR CARRIAGE M 12 t """:)J l 1\

7 \ oe». /'1 5 Z O 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 galvanised 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) 7 IMP'"

8 vehicle tarpaul in was stawed, and the footrest was formed fram the lid of a carbine box. The spade was raised 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 moving forward on counter rec oi I. The rea son for the brackets a ttac hed to the rear bogies is obscure. Some photographs appear to show wedges driven in between this and the track and it is suggested that they might be to stop the track jumping off the return rollers when the gun was fired. It cou ld be that they were to relieve she er stresses on the rear bogie, t' or act as supp orts for the sponsons. One of the items requ ested during the rebui Iding were sand shie lds otherwise there were no noticeable differences. A canvas co ver was designed to fit over the gun compartment to protect the crew in inclement weat her, 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 extremely dangerous For the gun crew. Considering the obsole te type of gun utilised, 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 utilised the for more modern 155mm gun M.2 on a wider and long er chas sis with Horizontal Volute Spring Suspension and 23" trac ks started coming off the production line in February 1945 and standardised in Moy 1945 as the MAO. At the same time the M.12 was reclassified as Limited Standard, being declared obso lete in August It is of interest to note that from the time the pil at was rec ommended the T.83 took exactly one year to sta ndardisa tion being approved. The onl y known rema ining example of the M.12 is retained at Aberd een Proving Gr ound, Moryland. The main series of scale drawings, by Phil Dyer, are the result of sever al yea rs work and research whic h includes detailed measuring of the onl y vehicle sti ll in exis tance at the Abe rdeen Proving Grou nd. These dr awings and the historical data whic h have been comp iled so ca ref ully by Phil Dyer and his many American friends are the most ac curate possib le with the material exists to-doy....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 ilot a lso with tailgate lowered. The M.12 shown is on early vehic le in vie w of there being a step down directly beh ind the gun mount where the looding platform was on the T.6 originally. ' I.r,,...,.J " 8 i 'f'.

9 Exc erpt from a Batt Ie Gr ound rep ort on the M. 12 "Bottle of Se igrie d Line" - bottl e of movement ended temporarily whe n the U. S. First Army re ached the German barder. The battle of the Sieg fried line be gan. Duri ng this bo ttl e the battalion hod a dual role: as on Artill ery batt a lion del iveri ng supporti ng fir e, and as a siege gun redu cing pillboxe s and other fixed fo rti f ic a tions in the ar ea. It is not possi bl e at this tim e to give a detai led technica l acc oun t of the use of the M. 12 as a siege gun. Most of the pi Ilbaxes destroye d or neu tra lised by the battalion are sf II an the other side of the front lin es. Some ge ne ra l obse rva ti ons ca n be mode even now, however. When the mobil e phose of the campaign e nded with the investment of th e Si egf rie d Line 'B' battery was det ac hed from the battal ion and attached to th e 9th Infan try Division for the specific purpose of dire ct fir e against pillbox missions in addition to it's regular ar ti llery work for the 3rd Armoured Division. From 15th to 24th Sep temb er., thi rty-fi ve direct f ire missions were assigned to the battalion. O f these twe nty - ei ght were pi llboxes and seven we re forti fi ed houses or observa tion posts. Sixteen of these missions were completely suc cessfu l. O n each of these missions complete destructi on of the pi llbox, penetra tio n, or di rect surr ender to the fi re of the M.1 2 wa s accomplished. On the remai ning nineteen missions vary ing degrees of neutrali sation we re ac hieved. In most of these latter cases it has be en possibl e to oc cu py the pillboxes or oth er struc tures on whic h the fi re was d eli vered, but from pri son er of war repor ts it is co nc luded that ca sual ti es due to concussion a nd chipping of concrete occurred in all cases. An overage of te n rounds we re fi red on eac h mission. Based On the exp eri enc es so for ga ined we be live tha t th e M.12 sui ta bly empl oyed, wi ll destroy, pen et rate, or knock-out of action pillboxes of the Siegfr ied Line type. The projectile produces cas ua lties and lowe rs morale of the pillbox occupants. No penet ration of the heavy 14 " ste el c upo la s whic h the be tter typ e pi Ilbaxes ha ve ar e known of. It is a lso d iffi cu lt to pen etrate the best type of concre te, but in some cases seven feet of co nc rete we re pe netra ted fa irl y easi Iy. The opt imum range for the piilbox work wou Id app ear to be between 1000 ond 2000 yards. At thi s range there is very litti e loss of accuracy or muzzl e ve loc ity, and the Crew are out of rang e of muc h of th e enemy's sma ll arms fire. Pill box att acks shou ld be c lose ly co - ordinated wi th the support ing infan try an d tan ks so that neutralising fir e ma y be deliv ered on the pillboxes whi le the M.1 2 is shoot ing for destr uction Most of the missio ns were fired by indivi dua l p ieces, but perh ap s massing the simultan eous fir e of several M. 12' s wou ld greatl y increase the con c ussion effec t as we ll as the sha tteri ng a nd pene tration of the co nc re te, thus conservi ng ammuniti on. Rood marches of 200 mil es ha ve been ac c omplished in on e day an d the ful l tra c k carriages ha s a lso mode possibl e crass cou ntry mobility BELOW: Preparing on M.l? for action towards the en d of the war in G ermany. The battery was bei ng ernp lcc ed for long ran ge fir ing, as insta nced by most of the gun c rew not bo thering to wear their helmets. In the foreground one shell is shown in the loadi ng tray, furthe r she lls are lay ed out on a ta rpa ulin to keep them c lea n. The crew member to the left is shown ca rryi ng twa of Ihe-ran ging rods use d in posit ionin g the gun. 9

10 " 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, Long tons Short tons Tonnes. Performance i Speed, Max. Road: 20 m.p h, (32 Km.p.h.) Max. Gradient: 22 degrees (40%) Fording depth: 3' 0" (91.4 cm) Trench crossing: 6' 0" (182.9 em) Step: l' 6" (45.7cm) Ground pressure: 12.6 Ibs/sq.ins (0.88 Kg/sq.cm) Range {internai fuel) Road: 190 Miles (306 Km) Dimensions Length overall: 22' 0" (670 em) Width overall: 8' 10" (269 ern) Height:(To top shield raised) 8 110" (269 em) Ground clearance: l' 5" (43.2 cm) Fire height of gun: 7" 2" (218 em) Road wheel dia (overall)l' 8" (50.8 em) Trackwork Centres: 7' 0" (213 em) Length on ground: 12' 8" (386 em) Width: l' 4" (40.6 em) Pitch: 6" (15.2 em) Number of links per track: 79. Type: Rubber Block Double Pin. Mechanical Detai Is Engine: Transmission: Steering: Suspension: Continental R-975C HP 9 cylinder air cooled petrol. Synchromesh SF IR Controlled differential Vertical volute spring. 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: Armour Hull, Drivers plate: Sides, upper: Decking: Engine covers: Gun shield: 10 rds, Imp gals. 200 U.S. gals. 757 Litres. 80 Octane minimum 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) Technical specification variation for Cargo Carrier M30. Crew: 2 Weight, Combat loaded: 45,580 Lbs Long tons 22.8 Short tons tonnes. Dimensions Length overall: 19' 10"(604 em) Height to MG ring: 9' 4"(284 cm) Ground clearance: l' 7"(48cm) Armament Main: Ammunition: 1 x.50 ca 1M2. HB rds of.50 calibre. 10

11 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 T6 - note the complex recoi I spade mechanism. Side view of the Cargo Carrier M 30. Side view of the 155mm Gun Motor Carriage M12 11

12 CARGO CARRIER T 14.AND M /44 Drawing and historical research by D.P.Dyer....- \ S ERI ES 22, No. 87(US) In March 1942 after:r e'ceipt of the Pilot T.6 it was realised that the amount of ammunit ion that could be carried in th is vehi cle would severely restr ict it's operation. A project was therefore initiated by the O rdnance Department for the devel opment of a companion vehicle based on the chassi s of the T.6 This vehic le was to corry additional ammunition and was to service the gun motor carriage. This was designated T. 14. The Field Art i Ilery Board reco mmended this de velopment in Ju ly 1942 (at the sa me time as they recommended adoption of the T.6) and authority was granted for procurement of fif ty. Mi litary character isti cs were approved in August and the soft plate pil ot model T. 14, toge the r with a produ ction M,12 had stowage arra ngements decided upon at Erie Provin g Ground by represe ntcflves of the Armored Farce and Field Artillery Board 'early in September. 38 had been co mple ted by early No vember. In view of production ha ving commenced prior to study of the pil ot model a lot of co nfusion oc cured wi th regard to modifications requested a nd it is not known ex actly how many T.14's were produced or when the y were completed. A recommendation fo standardisa tion of the T. 14 as Cargo Carrier M.30 Was made in September but ne ver appears to ha ve been approved although the Ordnance Dep ortm ent from then on a lways 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 rebuilding of the M.12's an d they were shipped ove rseas at the same time on the basi s of on e cargo c arrier to each G un Motor Carriage. Auromctlvelly the same vehic le as the gun ca rriag e the Cargo Carri ers differed in having stow age for faurty shells in place of the gun mount. A compartment to the rear of the right ha nd fuel ton k contained nine propelli ng c harges, ten were stowed in the centre of the vehic le behind the she lls, and a further twen ty-one in a comportme nt behind the left hand fuel tank. The rear of the ve hic le was formed by a ta ilgate whi ch wh en lowered formed steps for entry into the vehic le for loading and unloa ding. With the tai lgate ra ised the riser for the bot tom step (with the addition of c ushions) formed sea ts for thr ee gun crew members. A fur ther two seats were loca ted at the rear of the sponsons in line with the tailgate seats. The cargo comportm ent was surmounted by a ring mount for a.50 cal mach in e gun for anti-airc raf t an d loca l defence. As a point of interest the we ight of 155mm ammunition carri ed totaled ng tons(2.5 short tons) The M, 30 was dec lored obso lete a t the same time as the M. 12 and none ar e tho ught to be sf II in existence. BELOW, This ve hic le was the pilot Cargo Carrier T,14. Being converted di rec tly from the T.6 which had the sa me War Departmen"t Number It retai ned the rear track guards with a step up to the sponson extension s. The ties to the rear bogies were not tapered, and headlights we re mounted on the front track guards. Front a l v iews of the same vehicl e also show brackets for the gun rrove llng lock fitted to the drivers front p lat e (U.S. offic ial photo ) )f '-- =-=-- -

13 0 M W OIl:: -c U 0 C> Q::: -c 0 U 13

14 _. These two views show a productio n Cargo Car rie r T.14 with the tailgate lowe red. The.50 co l machine gun on the rin g mount is enclosed in it's protec tiv e wa terproo f cover. The brocket on the ri ght rear propellant ch arge compart ment cover wou Id appear to be for a spare.50 c a l mach ine gu n barr el. Grousers were conta ined 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. 14 (U,5. official photos)

15 ABOVE: In this view of T.1 4 numbe r 29 (U. S ) shown in travel ling order it wil l be noted tha t the dr ivers hood is in the ra ised position. This hood consisted of a fo lding canvos cov er with 0 transpare nt win dshield fit ted wit h a windscreen wiper. It was fitted over the drivers ope ned tap hatch for use when 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 out for deep wading, coming ashore during the Normandy landi ngs. It is interesti ng to see the way the deep wading screens hove been fit ted. Note the extended exhaust pipes on the sides. (I. W. M. Photo) 15

16 ABO VE; Unfortunately good quali ty phot ographs of the IS U series of Assault Guns a re not readily availab le, however, the photograph used here ill ustrates the gene ral lay out of one of the units fitted with the some gun as the IS I an d II ta nks. This model was known as the rs U S. SOVIET ISU GUN MOTOR CARRIAGE /45 SERIES 22, No.88/ 89 (SU) Historicol reseorch by J. F. Mil som. Drawings by K. M. Jones. During 1943 the Soviet High Command insti gated a progr amme for the production of a series of se lf-propelled a rti llery pi eces based on curren t Red Army ta nk chossis, In the hea vy cl ass, two weap ons were to be mounted on the KV chassis; thes e consisted of the 152mm M-1937/43 (ML-20 S) co rps howitzer and the 122mm gun M-1944 (D- 25S). Aft er unsucces sful a ttempts to mount these weapons in the o ld KV- II turret, more. sa tisfac tory solutio ns were ach ieved with ca semate mountings. These becom e de signated SU- 152 and SU- 122 respecti vel y. The 5U-122 consiste d of the Model mm gun mounted on a mod ified KV ch assis; the weapon was int erchangeable with the 152mm howit zer to form the 5U-152. Both were sta nda rd ized during Not long after produc tion was underway, howeve r, the 15-1 heavy tan k appeared o nd as a result newer more sa tisfac tory mountin gs for these weapons were de vel oped on th is c hassis. The weapons now beca me the ISU-152 and ISU-122 (D- 25S). The 15U-1 22 (D- 25S) was e nco untered by the Germans towards the end of World War II where it became designated erone ously as the SU-249. SU- 249 was a factory number a nd not the nomenc la ture by which the vehic le was gen erally known in the Sov iet Army. Aft er a short whi le produ c tion of the 15U-1 22 with the gun wos discontinued and further vehic les received the modif ied 122mm co rps gun M-1 931/37 (A- 19) and we re correspondin g ly design ated ISU- 122 (A-1 9S). This second vehic le has also been referred to as the 15U-122A and by the Hungarions, who wer e issued with several, as the 15Z-122. The ISU-122 (0-255) is believed to ha ve been produc ed either as a stop-gap measure to prov ide weapons to fie ld units dur ing World War II at a time whe n the Sovie t Army was short of a suitab le heavy assa ult gun, or it may ha ve been formed as a result of the unbal anced producti on of compone nt tank ports. The 15U-1225 were produced up to the end of World War II when production is believed to ha ve ceased. The 15U-122 (A- 195) consisted of a modified 122mm corps gun M-1931/37 (A- 19) mounted in a fixed superstructure 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 series of heavy tanks. Distinguishing features were its thinne r barrel and double-baffl e muzzl e-broke. The mantlet was smaller and more round ed that that of the ISU-122 (A- J9S). The supersturcture consisted of a full y-encl osed comportment mounted on the front half of the chassis. The front of the superstructure was set slightly back from the front of the hull. It consisted of a single piece, sloping plate, with a massive, two-piece mantlet mounted on the right-hand side. The montlel was co vered by a shield which was hinged to the right front of the roo f. Each side of th e supe rstructure 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. 16

17 i I} lr1 j I en u, C'I 1::1 C'I C'I... :::a en - 17

18 The rear pla te was vertica l a nd con ta ined a rec rcnqu lor access doo r an the ex treme lefr, This hatch cou ld be opened, e ithe r indep endently or in co njunc tion wit h on adj ac ent hatch on the roof, to form a sing le large en tra nce to th e ve hic le. The roof was f lat an d contained two rou nd hatches ne ar the front, in additi on to the rec ta ngu la r ha tc h at the left rear. The hull was the same as tha t of the 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 vent ext ending across the en tire width. The rear plate was broad, had a prominent shope a nd extended across the entir e widt h of the ch assis. Mudguards ex tended forward, beyond the chossis, at the fron t of the vehic le. The suspension system WaS the tors io n-bar type identi cal to that of the IS tanks, consisting of 6 indi vidu all y sprung doub le road wheels thr ee do ub le tra ck-support ro lle rs, and a rea r dri ve spro c ket on each side. The torsion bars exte nded th e full wid th of the ve hic le. The singl e -pin stee l trac k was approxim atel y 26 inches wide.. The armour varied co nsiderably in thickness on both the superstruc ture and th e hull. Ro lled a rmour plate was used ex te nsive ly on the superstruc ture, and the hu fl was mad e of sha ped castings. Armour thickness, whic h was greatest on the front, va ried from J90mm on th e mantl et to 90mm on the front of the superstruc ture. The sides of the supe rstruc tur e a nd the hu II were 60-90mm thi c k whereas the reor deck a nd the roof of the supe rstructure averaged 25mm thic kness, The engi ne was the same as that 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 HP at 2,000 rpm. The engine was wat e r- coo led and hod a pres sure-type lubrica ti on syste m. The fue l capacity has been est imored to be ga lls of diese l fuel c ontai ned in the main ta nks, each of four cy lindric a lly sha pe d ouxillicry ta nks wh ich may be carried on the rear dec k, a nd ea ch of two sma ller cylindrical ronks which were somet imes carried on the rear p la te. An additiona l ta nk could be carried be hin d the supers tructure. The armament of bo th mod els cons isted of 0 122mm gu n and a 12. 7mm AAMG. The main gun, used on th e ISU-1 22 (A- 19S) was the 122mm M- 1931/44 (A-19S) which was ba ll isti ca lly tlce some as the sta ndard Sov ie t 122mm corps M /37 (A- 19) from whic h i ;- hod been adopted. This gun hod a reinforcing ba nd on th e end of the barre l. The main gun used On rhe ISU-1 22 (D-25S) Was the 122mm M- 1931/44 (D-25S) which had the some ba ll istic cha racteristi cs os the 122mm tonk gun M (D- 25) used on all the IS seri es of heavy ta nks and had a doub lebaf f le muaz le-broke. Both we a pons fir ed sepa rate loadi ng ammunt ion and hod a range of approximatel y 16,000 yard. The ISU-1 22 (D-25S) had a high er ra te of fir e, 5-6 rou nds per minu te, whe reas the ISU-122 (A- 19S) fired only 3 rou nds per minute. The A- 19S fired slower be cause it hod a sc rew type breach-block whereas the D- 25S had a slid ing-wed ge type brea ch-block. A 12.7mm dua l- pur pose machi ne-gun (DsHK) was pe des ta l- mounte d forwa rd of the righ t- hand hatch on the superstruc ture roof of both ve hi c les. In add ition two trip od mounts were ca rried and two mac hin e-c arbin es, a. we ll as 25 han d-gren ades. BELO W: The more re gu la r version of the IS U 122 wi th th e A-195 gun. Russian Infa ntry ride On a n IS U during the fi na l stages af th e war on the East Front..-NOTE: Bello na Mi litory Vehic le Pri nts nor mall y used the vehic le desi gnati on in the namenc lotu reof the country of orig in on the grounds tha t this is the only correct title. In th e case 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 cepted" English " phonetic equ ivalent. Thus the accurate de sign a tion for th e Joseph Stol in tank is the IS, simi la rly the assa u lt guns ar e the IS U. The "G er man" phonetic gives 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. p..r:.::"sj

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20 IS U- 122 A - 19 S. Scale 1 : 48 ( -/I to l ' 0"). r.;',!:t""'\.,,, 'lq... -:===0 ===u I' '- Technical Specification for ISU-122 (A-19S) Crew: 5 Weight, Combat loaded: 101,470 Lhs Long tons short tons tonnes. Performance Speed, Max. Road: 23 m.p.h. (37 Km.p.h.) Cross Country: 10 m.p.h. (16 Km.p.h.) Max. Gradi ent: 36 degrees Fording depth: 4 1 3" (130 em) Trench Crossing: (249 em) Step: (100 ern) Min. Turning Circle: ' ( 9.3 metres) Ground pressure: 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 11 length overa II: 32' 2 110" length: w/o gun 21 Width overall: " Width over tracks: 10' 0" Height: 1w/o AAMG 8 1 3" Ground clearance: l' 6" Fire height of gun: 5' 11" Turret ring dia: None Road wheel dia (overall) 1 110" (980 em) (680.5 em) (356 cm) (305 em) (252 em) (45.7 em) (181 em) (56 ern) Centres: 7' 9" (236.5 em) Nt length on ground: 14' 8" (426 cm) Q Width: 2' 1.5/8 11 (65.2 ern) Pitch: 0' 61I (17.1 ern) Number of links per track: Type: cast manganese steel, dry pin. Mechanical Detai Is Engine: Transmission: Steering: Suspension: Armament Main: Calibre: Traverse: Elevation: Sights: 1 x Model V-2-IS litre watercooled, V12 diesel, developing 520 hp at 2100 rpm. Synchromesh 4-fwd. 1. reverse plus 2 speed auxi liiary. regenerative 6 twin steel wheels/side sprung on torsion bars, 3 return rollers/side. 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. Secondary armament: 12.7mm DshK AAMG M1938/46. on optional anti -ai rcraft mounti ng. Ammuntion, main armament: 30 rds mm Ammuntion, secondary armament: 500 rds, mm Internal fuel capacity: 66 imp.gals(300 litres) or 106 imp gals (482 litres) with additional fuel tanks. Type: Cast and rolled homogeneous. Hull, Nose upper: "(1lOmm)at 30 degrees Nose lower: 5.000"(J27mm) at 70 degrees Glasis plate /1( 75mm) at 74 degrees Sides, upper: lower; Pear; Decking: Belly: Superstructure Front: Sides: Rear; Roof: Mantel: Communications: Observation: 3.504/1( 89mm) at 15 degrees /1( 75mm) at 0 degrees 2.520"( 64mm} at 50 degrees O.984"( 25mm) at 90 degrees 0.748"( 19mm) at 90 degrees 3.543"( 9Omm) at 30 degrees t /1(60 to 75mm) at 15 degrees "( 55mm}at 0 degrees "( 30mm) at 90 degrees 7.480"(19Omm) rounded 1 x 9-R transceiver. TPU-3 laryngaphone. 5 periscopes. Technical Specification variation for ISU-122(D-25S}. Crew: 4 Weight: Combat loaded: 101,400 Lhs. Length overall: (1006 ern) He ight: w/o AAMG 8' 2/1( 250 ern) Armament 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 Sights: Tsh 17 telescope sight and diat sight. Armour Mantel: 3.937"(100 mm}rounded. " """,;:...:..._..._fhl!jiillli"'';" :. _,",.'-....Jo"'_.r.dl'...-"""". :."-. _,_...,J}.,...L...,Lt... '-'ll..l..,...""',...,..,.