Well I've read blurbs (short ones) in 2 different books that discussed the Ju86R huntings, and they said they stripped the cannons off, leaving only 2 MGs onboard. I guess both were wrong.
I can post you Galitzine's combat report where he talks about the jammed cannon. I heard him say it too. Well documented in "Spitfire-a Documentary History" by Alfred Price as well.
I think you are mixing up the two stories Krusty. In the Med they modified some Spitfire Vbs to try and catch Ju86P recce birds. They got 4 blade props, had everything stripped out, including radios and had their cannon replaced by 2 50 cals. They even went up with only limited fuel to save weight. Different Spits, different places, roughly the same time frame as the MTO bit was the summer of 42 and the ETO bit was Fall of 42.