Must agree with Hawkyns here...after thirty five years of handling paper cartridges and following period military drills, I have never come across a problem by priming first. If a trigger is that sensitive as to go off whilst loading, than I would wager that the half cock or dog is not working properly and such a piece should never have been passed by the safety inspectors in the first place. Also whilst loading, the shooter should be aware of where the muzzle of his piece is pointing, even if he is careless enough NOT to engage his safety...this is just basic shooting safety.
And not to milk the marine that had the accident at Hampton, from what he told my lieutenant, he had more than one cartridge in hand at the time...the one he was trying to load and an extra...