I can get the measurement for you
I will remove the one on my sons and give you the measurement for it. I would suspect something else as the cause of the jam though. I would suspect the ejector or extractor is having a problem first. Is the round coming out of the chamber and then not being thrown clear of the opening or is it just not coming far enough rearward to remove the round completely from the chamber? If it is coming out all the way and catching in the opening, I would think the ejector isn't throwing it clear. This could be an broken ejector, the extractor could be engaging into the rim too far, the carrier may messing up and rising too soon blocking the ejection. Let me know what the mechansism is that is jamming the gun and I should be able to help you solve the jam. The spring could be the cause, I will look and see if I can find a source for you on it. Good luck.
I tried Numrich and they were sold out. I will get the measurement for you.