I'll throw in a couple of points that I haven't seen so far.
The perception of delay is partly a personal and subjective thing, and varies with individuals. With anything slower than a fast center-fire, it's partly a matter of learning to focus on making the shot (and the follow through) and ignoring the things that are happening when you fire - parts moving in your peripheral vision, cap or priming flashing, etc. I am always aware of a flinter firing that small but perceptible bit slower than any center-fire, and if I fail to focus on the shooting to the exclusion of EVERYTHING else, I always hear the shot as clBOOM, not BOOM. Note that, unless there is a bit of a hang fire, I am not aware of discrete "clatch" then "BOOM", but I do hear the what I perceive as the beginnings of of the mechanical noise, even though the mechanics are completely finished before even the pan flash (see Pletch's videos). Heck, if I'm not focussing completely on the shot, I'm even aware of the hammer fall on my Parker Hale P.58 Enfield, although I don't hear anything different - just BOOM.
You may not need to pick the vent. Every flinter that I have owned with a chambered breech has had an internally coned touch-hole liner that has been generally self-cleaning of the touch-hole, excepting occasional partly contaminated powder or excessively dirty powder (bad lots of Elephant, for example). Thus, I rarely need to pick the vent to clean it, and I do not find an advantage in loosening or hollowing the powder just inside - I want to see grains of the main charge right at the touch hole. Since I don't want to exacerbate the eventual erosion of the rather thin-walled touch-holes in the liners when I do pick the vent, I use copper electrical wire hammered to a taper for a pick, rather than something as hard or harder than the liner material.
Regards,
Joel
p.s. I loved the M14 too - I shot well (for me) with even old well-used ones.