On June 1st 1940 - Britain had 14,023 Bren guns available which could equip 40% of the Army's needs - or more likely enough to equip the fighting companies needs but not the B echelon units etc - by the end of Aug this figure had risen to 59% (so they had made about 6500 Bren guns in less than 3 months)
So while not abandoning so many Bren guns is certainly a good thing it was not a serious issue facing the Army
The biggest short falls were in Anti tanks guns, artillery and AAA and it was here that there was a slow increase in the replacement in the months following Dunkirk
25 pounder production was still ramping up and modification of the entire 18 pounder "estate" to the 18/25 pounder guns was nearly completed (with many of the guns already converted lost in France along with a number of unconverted guns).
So there was not a lot that could be done to restore the shortfall other than continue to ramp up 25 pounder production.
The following shows tanks and carriers in the hands of the army between June 30th and August 31st (all figures OTL)
| Infantry | Cruiser | Light | Carriers |
June 30th | 140 | 209 | 582 | 2,242 |
July 31st | 218 | 284 | 657 | 3,181 |
August 31st | 274 | 322 | 659 | 3,784 |
The period between June 30th and August 31st sees an increase of 134 Infantry tanks, 113 Cruiser tanks and 1,542 carriers of all types. Infantry tank production is steadily increasing from 57 in June to 90 in August, Cruiser tank production is decreasing dropping from 58 in June to less than 30 a month by the end of the year. Carrier production has increased dramatically during the year to over 500 a month by May. Infantry tank production peaks in December with 127 tanks in that month alone.
ITTL we are likely to see more of the Infantry tanks having been completed with Vickers Valiant production now ramping up (in addition to that of Matilda II) and I suspect that this would cut into the Cruiser production slightly as while the existence of the Vickers Valiant production would have resulted in a subtle increase in all things AFV related it would still have resulted in a shortage of certain common parts as the 3 production lines (Matilda II, Crusier tanks and Valiant) compete for them.
For example I have seen several comments regarding the sooner replacement of the 2 pounder gun with 6 pounder - which we all agree would be a great thing.
However 2 pounder production had been ramped up by June 1940 but I suspect that the slow increase we see post Dunkirk in replacement 2 pounder AT guns in the hands of the Infantry was primarily due to the numbers required to 'also' arm the Infantry tanks, then A12 Matilda II and Cruiser tanks which would have been 247 guns in the period June 1st - August 31st - here we are adding further Valiant tank production to the mix.
To switch production from 2 pounder to 6 pounder would have IIRC taken several months and cost the production of 600 x 2 pounder guns for just 100 x 6 pounder guns - and so this would have prevented hundreds of Matilda II and Cruiser tanks from being armed (with many of them being sent to the Middle East) and this at a time when as you can see from that link the table of establishment for anti tank guns in the infantry Divisions was only 1/4 of the number required by the end of Aug.
So I am afraid that the switch to 6 pounder simply cannot happen until this shortfall has been addressed.
There is a reason why we do not see the adoption of 6 pounder tanks and anti tank gun batteries earlier than we do.
Also remember that British industry was sleepily equipping 5 Divisions in 1938, then suddenly it was woken up to equip 10 in 1939 then err actually can we make that 32? And then in June 1940 - Oh fuck actually make that 55.
An 11 fold increase in less than 3 years was not possible - on top of this mad rush to build a continental army the losses of equipment in France particularly in Artillery of all types was a major issue in the months following Dunkirk.