ARM: Book Review - the Sexton SP Gun in Canadian Service

Book Review: "Weapons of War" Series; The Sexton SP Gun in Canadian Service by Doug Knight; Service Publications, Ottawa, Ontario, Canada,
2006; 24 pp. with B&W photos; price CDN $9.95; ISBN 1-894581-32-6 (http://www.servicepub.com )
Advantages: Good, clearcut description of how the Sexton came to be and its developmental history, along with some information on organization and details
Disadvantages: modelers may regret not having more detail information on regiments and markings
Rating: Highly Recommended
Recommendation: For all "gonners" and Commonwealth fans
    One of the myths of the Second World War which has unfortunately come down to us is that the Canadians copied many US designs, when the fact of the matter is exactly the opposite. The Ram tank was an original idea, and not a copy of the Sherman; likewise, the Sexton was an original design and not a copy of the M7 Priest.
    In March 1942 the Canadians, who were then primarily modeled on the British Commonwealth pattern of equipment and unit organization, decided to create self-propelled artillery to support their own forces and if needed to provide support to the British Army. Having the mechanically reliable and flexible M3 Medium Tank chassis available, they experimented with fitting the then standard 25-pdr field gun to it as a self-propelled weapons system. Three months later Montreal Locomotive Works (the Canadian subsidiary of the famous ALCO locomotive company in the US) produced a wooden mockup followed by a prototype in July. After testing and getting the kinks out of the design, it was shipped to the UK for trials.
    Even while it was under testing, the Canadian government ordered 84 of the new guns for their own artillery units. Fitted with a tank compass so the driver could get a rough bearing alignment of the gun for firing, the system was shown to work well. Tests at Larkhill in the UK showed the gun to be amazingly easy to deploy and operate, coming into action in 20 seconds and being able to change firing positions in less than 90 seconds. The comparative tests were such that the British decided to stop use of the American M7, now dubbed the "Priest" and opt for the ammunition-compatible 25-pdr SP gun. In May, the new weapon was given the formal designation "Sexton" (following the Priest, the British gave all of their SP guns clerical names, such as the Valentine based "Bishop" and the postwar 105mm "Abbot.")
    Sextons were organized into three-battery regiments of eight guns per battery (two sections of four each) or 24 guns total. Later, Ram OP Tanks were provided along with "defrocked" Sextons as Gun Position Officer's vehicles for battery level fire control. On occasion these regiments were refitted with M7 Priests, such as for D-Day, but the preferred vehicle was the Sexton. The British and Canadians preferred the 25-pdr as it outranged the M2 series 105mm howitzers, and the 25-pdr shell was considered nearly as effective on target as the larger 36-pound projectile thrown by the 105mm howitzer. Also the vehicle could carry 105 rounds of ammunition (normally 87 rounds HE-FRAG and 18 rounds AP.)
    A number of details are covered, such as most of the Sextons came from the factory fitted with Canadian pattern dry-pin tracks. However, most of the photos show that they were not kept long in the field and were replaced by one or another of the standard M3/M4 medium series twin-pin track sets. Just about every major type is shown in this book, so the modeler can rest easy about building a model of the Sexton.
    Overall this is a handy little book about one of the more popular - and long-lived, with some serving as late as 1964 in Commonwealth forces - self-propelled weapons. A set of 1/35 plans by George Bradford are provided as a centerfold, but no markings or coloring data is included. (Also see their books on the Ram - Parts I and II - and the 25-pdr for additional details.)
    Thanks to Clive Law for the review copy.
    If you mention the term "divisional artillery" to anyone from the Second World War who knows artillery, four guns will immediately be mentioned: the German leFH 18 10.5 cm howitzer; the US M1/M2 series 105mm howitzer; the Soviet 76.2mm ZIS-3 gun; and the British 25-pound Field Gun. All four were by far and away the most used weapons of their type by their respective nations, and provided most of the "on-call" artillery fire support for their troops.
    The British 25 pounder (so-named for its nominal weight of shell) was a linear outgrowth of the pre-WWI 13-pounder and its much-improved 18-pounder replacement. In point of fact, as Doug points out, the 25-pounder began as a new barrel created from older 18-pounders by boring them out and using "auto-frettage" - prestressing the barrels from the inside out to make them lighter and stronger - to tolerate the larger shells and greater propellant charges. These guns first went into service in 1936, and eventually received a new carriage and cradle assembly.
    The standard version, the Ordnance QF 25-lb Mark II on Mark I carriage, was the standard field gun for Commonwealth forces during WWII and long afterwards, until NATO called for standardization on 105mm and 155mm as divisional calibers in the mid 1950s. Like all things from the Commonwealth, Canada again stepped to the plate to produce its share of guns, and using a new ordnance factory built at Sorel, Quebec, just prior to WWII with the help of the French Scheinder company, the 25-lb gun went into production in 1940, with the first guns delivered in July 1941.
    Doug covers the entire production history of the weapon as well as a great deal of other information, including regimental organization and function, crew organization and function, and some items on both the well-known No. 27 limber (a leftover from horsedrawn days according to all who used it) and the FAT - field artillery tractor. Produced by both Ford and GM of Canada, these well-known vehicles with either the flat windshield No. 12 cab or more popularly known No. 13 cab with reverse slant windshield were probably better known and more prolific than the Morris tractor that inspired them.
    He points out how anachronistic much of the artillery thinking was involving this weapon, as the crews hated the limber. (Point: try backing up with a trailer towing a trailer and that you can't see either one, and you start to get the idea of why this hatred came about.) Also someone noted when the crews deployed for action one man stood alone at the rear of the piece with no apparent function. Someone finally figured out that he was the "horseholder" from the old days and nobody thought to eliminate him from the crew!
    The 25-lb gun was not the most powerful or longest ranged weapon on the battlefield, but Doug points out where its strengths were and why it was popular. One point he makes is the gun fired a projectile only slightly smaller than the US 105mm (25 pounds versus 33 pounds) to the same range and with a smaller and more easily handled gun. The 25-lb barrel was also more long-lived. Artillery weapons' life expectancies are based on how many "full charge" (e.g. tabular charges for reaching maximum range as designed without any modifications to the charge or projectile) rounds could be fired: for the 25-lb gun, it was 10,000 effective full charge (EFC) rounds. To put this in perspective, Soviet sources note that their powerful long range 2S5 152mm gun only had a life expectancy of 300 EFC rounds, and that the early T-72 125mm 2A46 gun had a life expectancy of only 200 EFC (e.g. sabot) rounds. Of course, firing reduced charges increases life expectancy and "super-charges" reduce it (e.g. each "super-charge" is rated at 4 EFC for life expectancy computations for the 25-lb gun). He notes that some guns were still fitted with their original barrels when placed out of service in the 1950s.
    Overall this is a very handy little book, as it also explains a great deal of artillery operations and functioning. I only noted one minor error - in the description of the weapon on page 24 the length of the gun is given as 25 feet 10 3/4 inches; it's not, as that is the complete length of the gun, No. 27 limber and FAT in march order from tip of the front towing pintel to the end of the muzzle brake on the later production guns. (The Canadian vehicles can be modeled in 1/35 scale using the Tamiya 25-lb gun and limber and the older Peerless Max/Italeri/Zvezda FAT with No. 13 cab, or in resin using various manufacturers in 1/76 scale.)
    Thanks to Service Publications for the review copy.      Cookie Sewell
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