With regard to the 17 pounder debate, as well as the ammunition issue, I would refer people to the following site.
ANTI-TANK
It has two salient points to make, IMO. The distribution of 6pounder/17 pounders in the late war British Infantry formations, and secondly the effectiveness and issue of the various ammunition types, and why
Distribution of ATGs to Inf Divs
"By September 1943 the official position for European Theatres was:
Regiments in infantry divisions - 4 batteries each 8 × 6-pdr and 4 × 17-pdr in 3 troops.
Regiments in armoured division - 2 batteries each of 12 × 6-pdr, and 2 batteries each of 12 × M10 in 3 troops.
Corps regiments - as for armoured divisions.
At the beginning of 1944 the official WEs permitted divisional anti-tank regiments to comprise 4 batteries each with 8 × 6-pdr and 4 × 17-pdr, or 2 batteries with 12 × 6-pdr and 2 with 12 × M10, or 4 batteries each with 8 × 6-pdr and 4 × M10.
However, there was considerable dissatisfaction with these organisations, what was wanted, and was duly agreed and approved was:
Regiments in infantry divisions - 4 batteries each 8 × 17-pdr and 4 × 6-pdr in 3 troops.
Regiments in armoured division - 2 batteries, each 12 × 17-pdr, and 2 batteries each 12 × M10 in 3 troops.
Corps regiments - as for armoured divisions.
The following month a specialised anti-tank battery organisation was approved for 'assault' units (meaning amphibious assaults). These batteries had 2 troops of 6-pdr and 1 of M10. The reason for this was the policy that only tracked vehicles would cross the beaches for the first 8 hours of a landing. However, in August 1944 experience in Normandy led to a revised organisation for batteries in infantry divisions, a merging of the 'normal' and 'assault' organisations. Batteries became 1 troop 6-pdr, 1 troop towed 17-pdr, 1 troop SP 17-pdr to provide an effective mix of capability reflecting strengths and weaknesses of the various guns.
Starting in 1943 infantry type divisions in India had a composite LAA/ATk regiment instead of one regiment of each as in western theatres, although most divisions in India had never had an LAA regiment and a LAA/ATk regiment had been formed a year earlier, possibly for the Indian armoured division. These regiments were generally formed by a pair of LAA and anti-tank regiments exchanging two batteries. They lasted until September 1944 when all the LAA/ATk regiments in 14 Army became anti-tank regiments with 3 batteries, dual equipped with a 6-pdr anti-tank gun and 3-inch mortar for each of their 36 detachments.
Anti-tank was the one area of artillery organisation where there was national diversity. By the end of the war Canada had two types of anti-tank regiment, corps and armoured division regiments had 48 guns 50:50 towed and SP 17-pdr, but infantry division regiments had only 36 guns, still 50:50. Australia retained the 48 gun regiments, all 6-pdr, for the home defence divisions, but the jungle divisions were reduced to a single battery from a corps anti-tank regiment. All Australian anti-tank regiments were renamed 'Tank Attack Regiments' in 1943. In the final year of the war the AIF divisions' retained their tank attack regiments but anti-tank was little used and Australian batteries employed 4.2-inch mortars, 75-mm howitzers and acted as infantry."
Effectiveness Of ATG guns and ammunition
"Most British anti-tank ammunition during WW2 was solid shot, which relied on kinetic energy to penetrate armour. KE is the product of the mass and velocity of the shot. However, soon after WW1 an armour piercing HE shell had been developed for the 18-pdr field gun (such shells had been common for naval guns), and the original design of 25-pdr ammunition had been for an armour piercing cap for 25-pdr HE, this design was unsuccessful. Later in the WW2 a shaped charge (HEAT) shell was developed and issued to 3.7-inch Howitzers in Burma, although in the event it was never needed. HEAT was also used with the PIAT. To these can be added work on recoilless guns, including the 4.7-inch anti-tank using HESH that led to the post-war 120-mm BAT family, during the war the size of its ammunition and its logistic implications found little favour.
Wartime developments in anti-tank (and tank) gun ammunition addressed two matters, improving penetration of shot and flashless propellant.
At the outbreak of war the standard anti-tank ammunition was a solid armour piercing (AP) shot fitted with a tracer. Throughout the war anti-tank guns used fixed ammunition (ie the cartridge and shot were a single fixed item, unlike other artillery ammunition). Improvement to the penetrative capability of AP shot went through 5 stages:
Fitting a special cap to the nose to prevent it shattering at oblique impact angles, called Armour Piercing Capped (APC).
Fitting a streamlined ballistic cap over the AP, this reduced in-flight loss of velocity and increased penetration. It was called Armour Piercing Ballistic Capped (APBC)
Combining APC and APBC as APCBC. This entered production for 2-pdr in February 1943, for 6-pdr in April and for 17-pdr in August of that year.
Using a solid alloy body, highly tapered in shape, around a tungsten steel core, Armour Piercing Composite Rigid (APCR) was introduced very briefly for 6-pdr, and does not seem to have ever reached units in action.
In the summer of 1944 discarding sabot shot (APDS) was introduced. This was a tungsten carbide sub-calibre core in a light metal casing that fell apart and dropped away from the core when in left the muzzle.
APDS provided better penetration than APCBC but the latter did greater damage when it penetrated so both were used with APDS being used when penetration by APCBC was less than certain. In addition there were practice projectiles (PP) for all calibres. These were generally reduced in lethality and range. AP shot was available for 40-mm Bofors LAA guns throughout the war. However, HE was useful, during the first German attack on Tobruk the first rounds fired at tanks by 25-pdr were HE. The first caused a Pz KfW Mk IV to catch fire, with the second another tank lost its turret.
The following table summarise the main characteristics of anti-tank ammunition, most were fitted with tracers and there were also practice rounds for each calibre. The penetration figures are for standard tests and should be viewed in terms of their relativity and not actual penetration of tank armour."
Summary of Anti-Tank Shot Characteristics
Ammunition
Calibre
500 yds, 30°
1000 yds, 30°
2-pdr AP
53 mm
42 mm
6-pdr Mk II AP
75 mm
63 mm
6-pdr Mk II APC
88 mm
6-pdr Mk II APCBC
95 mm
6-pdr Mk IV AP
74 mm
6-pdr Mk IV APC
Unknown
6-pdr Mk IV APCBC
Unknown
6-pdr Mk IV APCR
100 mm
6-pdr Mk IV APDS
143 mm
17-pdr AP
123 mm
113 mm
17-pdr APC
118 mm
17-pdr APCBC
Unknown, not stated
17-pdr APDS
231 mm
25-pdr Mk 2 AP
62 mm