Measurements of Stock barrel

Wondering if anyone can help me out by giving me the stockmeasurements of the j10 inner barrel length and ldt hk416.
I have just ordered X2 gold bruise masters, ready to order barrel extenders, but won’t be returning home for another week to measure up length.

I swapped the stock j10 for an alloy but I’m pretty sure it’s the same length as the default stock plastic one, fits inside the flash hider, and the LDT is standard with an alloy already so haven’t swapped that yet.

Thanks guys

Would this fit a 40cm inner barrel?

And if anyone has any links for any ldt hk416 that would be great.