This went a lot easier than I thought, so far.
I loaded up a batch of test rounds, to just off the lands -COL = touching lands less a fraction.
Started at 34 gr S335, 35 gr and 36 gr

First mistake was that I did not measure magazine length, so rounds were by some miracle just able to fit into mag with some bumping, pushing. After each shot I had to bump or rattle the next round up in mag - it was that close a fit.
Secondly I shot at 50 m, because I was really expecting from what I had heard, to perhaps not be on page with first tester rounds.

Imagine my surprise!  First shots in Yellow highlight. 34 Gr
Third tester lower group at 36 gr
I had to discard the 35 gr group because  I again FORGOT how fast the .303 barrel overheats and starts string shots, 4 slow wait between shots and still the second group was not usable.
20240114_130432 by David Frank Allen, on Flickr

Nice!

Any idea what the velocity was?

Just over 2moa?

Secondly I shot at 50 m, because I was really expecting from what I had heard, to perhaps not be on page with first tester rounds.

Imagine my surprise! 

Since going down the rifle bullet casting rabbit hole I've come to the conclusion that much of what is spouted about the subject is from people who have little if any direct personal of making the bullets or developing loads for them. 

I now have to ask - did you record speed?

Any idea what the velocity was?

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No I do not Know  :-X

I now have to ask - did you record speed?

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Oom Drie, when I arose to go to range, I awoke, took range box,target stand, rifle and test ammunition - got in car and drove off. When I got to the range I wondered about things like targets, batteries and had I paid my membership fees this year.
I do not think I have reloaded in over a year and I do not think I have used the club range in twice that time. I just went into a dead zone in that regard, happens when you have 2 - 300 rounds already loaded and you a hunter not compo shooter
It can be said I buy new rifles so as to have something to reload for.

Regardless of above, your said "correct load" and result were spot on, the 36 gr suggested is the winner. I will now load some loads in half mm shorter increments to see if there is a betterment in group - I can not load even .2 mm longer. I will be sure to have chroni and batteries for the event.

Keep us posted. Measure the water volume of a few fired cases as well as the barrel length to a cocked action (removes the firing pin) with a cleaning rod.

Also record COL from base to tip of bullet.

Keep us posted. Measure the water volume of a few fired cases as well as the barrel length to a cocked action (removes the firing pin) with a cleaning rod.

Also record COL from base to tip of bullet.

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Shall do so.