If (and assuming the typical paper puncher/plinker/critter hitter/sport shooter type):
1. You are in a very dirty environment (desert, dusty, dirt, etc...), you probably could benefit from a dust cover.
2. You are going to lay your weapon on the dirt as the guy in the video did, you probably could benefit from a dust cover.
3. You are in the rain, although not a waterproof seal, you probably could benefit from a dust cover. (because it will help keep direct rain fall from entering the weapon).
4. You plan on covering the rifle with dirt or intentionally throwing dirt into the weapon, you probably could benefit from a dust cover.
5. You plan to produce movies showing intentionally treating the weapon in an unrealistic manner as shown in the video above, you probably could benefit from a dust cover.
6. You have a requirement, policy, necessity, need, or have made a choice, to have a dust cover, you probably could benefit from a dust cover.
7. You have a requirement or policy that when a weapon is not in use and racked or stored the dust cover will be closed, you probably could benefit from a dust cover.
Now, why do I say that "you probably could benefit from a dust cover" in 1 - 7 above? Aside from a practical application, its because generally people who can aford to intentionally mis-treat their rifles like in the video just for the sake of showing an unrealistic point (guy even mentions at one point its unrealistic) are not generally the people who shell out their cash to buy your weapons for you so this means the choice is up to the individual weapon owner.
The video has nothing to do with the dust cover really, the guy is demonstrating the weapon function even when subjected to dirt (which indicates the need for a dust cover anyway). If he had the dust cover shut all the time then he probably would not have had much of a video. If you have a dust cover or don't have a dust cover, its your rifle and the choice is an individual choice to have or not. I don't see why people get so "do i need a dust cover..." discussional and confused when the choice is theirs. If you have one it doesn't get in the way and doesn't hinder you - if you don't have one it doesn't get in the way and doesn't hinder you - it all comes down to what the individual wants for their weapon, their needs, their requirements, and their use of the weapon.
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I personally think a dust cover is needed for a platform like this. I'd rather have it and not need it than need it and not have it, plus I have a need for a dust cover on my weapons, and I close mine all the time when the weapon is not in use. Training, education, experience tells me a dust cover is needed, of course I do things with my weapons the average shooter doesn't. There is a reason why the dust cover exists. However, for the paper puncher/plinker/critter hitter/sport shooter type its something they can choose to have or not and would probably not suffer any consequences from not having a dust cover if their weapon is not subjected to the things in the seven items above (or in the video).
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