So to boil it down we're concerned abotu speed and convenience? Then why aren't DBMs the be all and end all rather than a floorplate? Certainly a floorplate is fast to unload, though likely slower than a DBM. But a hinged floorplate is no faster to reload than a blind magazine so where is the convenience issue? How much time is saved and is this relevant or simply an exercise in debating minutae? The argument that we give our troops a DBM has no bearing on the hunting field. The military asset may be called upon to deliver a large volume of fire in a short period of time and will be doing so with (hopefully) the assistance of cohorts. If grunt #1 has a mag take a dump the rate of fire doesn't go to zero and he can change the defective mag out and get back in the fight. If something goes south when you are in the alders following up a grizzly or in the jesse with a body-shot elephant and your rifle takes a dump you may well end up dead because there could be no help standing next to you. Thus, the blind mag is foolproof.
For some folks they are, but I have two problems with DBMs. First is that they don't improve the look of many of the rifles they were added to as an afterthought, but more importantly, I tend to leave the damn things behind. Now clearly that is my failing and not the DBM's, but the fact remains, I don't leave the magazine at home if I remember to bring my floorplate equipped rifle with me.
The speed of reloading is the same for all 3 types of magazine. If you want, or need, to reload quickly, have a stripper guide machined into your rear bridge and load with strippers. DBMs might be a tad quicker to reload if you have more than one, otherwise they offer no advantage in the speed of reloading, but at some point the ammo has to be stuffed into the spares as well. I doubt that bolt gun reloading can be accomplished any faster with a magazine swap than with strippers.
With respect to one's rifle failing at the moment of truth in a close range dangerous game scenario, again the onus is on the hunter to ensure the reliability of his rifle is as close to 100% as is possible. The thought of a floorplate coming unhinged, dumping the rounds on the ground as the hunter is charged is truly a nightmare scenario, and if the idea keeps you awake at night you can tape or pin yours closed, or as you point out, choose a blind magazine. The reality is though that a good quality, well maintained floorplate is as likely to break at the critical moment as is your extractor or the firing pin that you've exposed to thousands of dry firings in preparation for this moment.
Some individual rifles though have idiosyncrasies that require special consideration if they are going to function reliably. An example is my custom Brno 602 .375 Ultra. If the rounds in the magazine were pushed to the rear of the box, it was possible for the bolt face to slip past the top round without picking it up, due to the rebated rim of the Ultra case. Thus when loading, I had to ensure the top round was pushed forward until the nose of the bullet contacted the front of the box (actually the bottom of the feed ramp) the round then was reliably picked up and the recoil of the first round properly indexed the subsequent rounds in the magazine. If your rifle has an issue as easily resolved as that, it doesn't need a great deal of attention, but failures that take it out of action are not acceptable and must be addressed prior top going afield.
But, is the blind magazine foolproof? Fools shouldn't operate machinery, but I doubt that the blind magazine is worthy of your praise. If your rifle is exposed to rain, snow, dust, sand, or gets dunked in a swamp, there is no convenient way to clean out the magazine short of taking the rifle apart. If you take the rifle apart, get it all cleaned out and back together you cannot be absolutely sure that your zero hasn't shifted, so now you have to confirm your zero. Compare that to opening the flooorplate, clearing the carumba that has collected there, wiping it dry, closing it up, wiping off the ammo, reloading and being on your way. By the way, this is where Mauser style bolts that can be disassembled without tools have an advantage over their modern counterparts as well.
I recall hiking along the coast one day, stopping for a beak, and propping my freshly cleaned and oiled 590 against a rock. My dog of course managed to get tangled in the sling and knocked the gun over into the fine beach sand which instantly coved every surface it contacted . . . inside and out. And of course we hadn't walked 100' further when we met up with a rather large polar bear in the rocks. The gun wasn't completely out of action, but I was fortunate that I didn't have to shoot. Some days s**t just happens, and thats when you find out just how foolproof your gear isn't, and discover just how easily you can be made of a fool of.
