First again, nice work on that.
In my opinion you should have a look on the prod mounting it seems a bit out of center.
I think you should shoot a heavier bolt, too, but I am not agreeing with the formulas used to calculate the energy.
First of all, you can never apply the same energy stored in the prod into a kinetic mass.
Especially for crossbow steelprods.
You must consider the mass of the prod and the string has to be moved, too.
And you always have a certain amount of friction which decreases energy transfer.
Even a roller nut from steel takes it´s energy.
You should try out heavier Bolts in 10g steps (40,50,60 and perhaps 70).
At least when you built your chrony. (looking forward to it)
Most of my ressources state to get to 60-65 m/s with a steel prod in safe operating conditions.
So this seems very fast, lets have a look if the chrony can proof the data.
How much is the prod weight? 920-960g ???
Most crossbow prod weights related to the belonging bolts I know from different german sources are in relation of 1/45 or 1/48.
But the problem ist these were mostly very heavy prods (commonly ~3kg on a "Halbe Rüstung") with higher draw weights than we use.
It is not that easy to compare with our low weight modern replica bows.
So with around 3kg prod weight the bolt would have 60-70g.
Not that easy, you should make tryouts to get into the best speed mass(energy) relation.
And ft it sounds to loud, it would be a hint of too much dryfire.