It's no small secret that a great number of vehicles ordered by the USSR through the Lend Lease program. Most of the issues with missing gear were solved very quickly, or so I thought. This table shows that missing weapons continued to be an issue until the end of the war. The number listed in the numerator is for weapons that were supposed to arrive, the number listed in the denominator is for weapons that actually arrived, split up by year. The second last column shows the total number of the weapon that was ordered and that arrived. The last column sums up the difference.
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The 76 mm howitzer, 76 mm gun, 75 mm gun, 57 mm gun, 40 mm gun, and 37 mm AA gun all arrived in full. However, once you get to the 105 mm mortar, there is an issue, with a shortage of 114 units throughout the war. The 50.8 mm mortar (2" smoke grenade launcher in British vehicles) is also missing 450 units. The 25.4 mm (1") flare gun rounds out the missing launchers, 1055 units short.
Moving on to small arms, the 13.97 mm Boys ATR shipped a whole 1850 units short, with barely any arriving, not that they were all that likely to be used at all. The American 12.7 mm Browning MG is the only item in this section that had no units missing. The 11.43 mm (.45) Thompson SMG came up 2339 units short, 7.92 mm BESA MG was 36 units short, the 7.7 mm Bren MG was a shopping 2628 units short, but the 7.62 mm Browning MG takes the crown. The Soviets counted 3928 of these weapons missing.
Aside from weapons that came with tanks, there were also some spares. So many spares, in fact that a surplus formed. This table has the same structure as the previous one, with the number of weapons arrived in the numerator, number of weapons expended in the denominator, and total surplus at the end. Comparing the leftovers to the deficiencies above, you can see that the difference isn't quite made up. A number of Lend Lease tanks had to go into battle lacking weapons.