On second thought I realise that I have been less than my usual helpful self. As a sound engineer I can't help picking up some knowledge of film and the syntax therein, so notwithstanding Finius' comment, here's a few tips:
You need to engage the audience's interest immediately. In a much travelled amateur genre like this we need to know from the first few seconds why we should continue watching. Clips of bits to follow which promise something cool are an easy way to do this that require no skill in screenplay writing. Such clips should tease, not deliver.
Whether you mean to or not you are competing with a million and one other things a person could be doing other than watching your vid. For whatever reason the audience have clicked play, in doing so they did not sign a contract to watch to the end. This is where a screenplay comes in, because the moment the audience think, "this lad has no idea what he's gonna do next", is the moment they also wonder if they can be bothered to find out. That does not mean that everything should be scripted, although bullet points of what you intend to say on a large sheet of paper behind the camera will help keep it snappy. It does mean that you should think about what shots you want in the finished product and how long each should last.
This is going to seem apropos of nothing, but all will make sense anon* - An aircraft simulator is attached to the ground and the hydraulics can only travel so far to simulate the effect of stick movements IRL. So when the trainee 'takes off' the cockpit front tips up and levels out from the rear when the 'plane' reaches cruising altitude. So what happens when he pulls the stick back again? There's not far to go before the machine is at the limits of the hydraulics, right? Well it's all cool because the computer is programmed to imperceptibly bring the cockpit back towards zero the whole time, so there is always some virtual space for the machine to go into.
A well written screenplay works in the same way with emotional reaction. It doesn't matter what the emotions are, from mild curiosity to euphoric epiphany, via disgust, anger, sexual arousal, humour, whatever, they can be summed together as 'stimulation'. The reasons are extremely complex and, if you are resistant to this next idea, you will no doubt be able to think of examples which you believe prove it wrong, but trust me we humans have a limit to how much stimulation we can feel, particularly from something which requires "suspension of disbelief".
Ah but what is to disbelieve? It's a film of exactly what happened, right? Well, A. that is not how humans experience events IRL, and B. the stimulation is a result of what happens in the film, but in reality what happens is we just watch a screen. It's a bit like seasickness - if there's too much of a disjunct between the degree of an emotion we are stimulated to feel and what we can feel while, say, sat at home in a comfy chair with a nice cuppa, the brain goes "hang on a minute, something isn't right here".
This is why the most engaging films and/or music have bits where the intensity of stimulation, having been ramped up at the beginning, imperceptibly falls so that it can rise again. There are many ways pros achieve this but with the least understanding amateurs can do it by picking an engaging piece of music for the background and writing the screenplay to follow it, then editing the shots to fit exactly.
You can also substitute one type of stimulation for another, to give 'room' for the first to come back later. An easy way to do this is to lower the volume of the music and give the technical details (intellectual vs anticipation/comedy etc), then raise the volume again as you get on with the destruction. Even better would be to do some tech deets, about the gun say, raise the volume briefly for a good bit of tune while you show some tease clips, say holes appearing in paper targets followed by hit empty cans jumping about, then drop the volume again while you tell us the deets about the screen.
The major thing you've missed out on though is that a screen is a visual device! Why don't we see it working at least once ffs? But imagine what you could have done by shooting it whilst a film was playing? A bit of thought and you could have had a clip show so you could shoot it and have the characters (or real people) seem to react to being shot.
A major thing which amateurs almost never give enough thought to is to plan the project around the limitations of the equipment. For eg, if you can't use an external mic, stop talking before you walk away from the camera and under no circumstances whatsoever should you turn away from the camera whilst talking. Again it's about suspension of disbelief - anything which calls the attention of the audience to the fact that they are watching a vid rather than keeping them focussed on the content is bad. Poor intelligibility due to obvious technical limitations is a major cause of this. If you need to give information while somebody walks away, have somebody else say it close to the camera, or think of a different way of presenting the info. If you don't need to say anything, shut up!
I'm getting bored now, so rather than more generalised tips, I'm going to just critique:
- you should have realised that we would not be able to see the BB's in flight, or the damage happening from that range, using that camera. Setting the camera much closer to the screen would have helped and you could have done an interesting sequence of zooms and cuts to segueway from showing yourself sighting down the rifle to a close up of the screen.
- you should have put some black cloth behind the screen so that we would have been able to see glimpses of the BB's trajectory on their way and bouncing off.
- you should have shot the frame to sh!t as well as the screen itself.
- you should have shown us the computer you promised to shoot at the end, with some ominous music.
- small moments of 'human fallibility' are good for audience engagement, so don't edit your shots to robotically fit your screenplay, find a few, and I mean few, bits where you can keep some fluffed line, gormless expression, or other mistake/uncool moment. You can make this self-consciousness cool by synching three quick repetitions (less than 0.5s each) to the beat of the background music. If your tune is slower than 120bpm, use the half beats (syncopated jazz woo-hoo), or the quarters, leading to the end of a section of the music. You must follow this with a cut to a completely different shot.
- you've got far too much um-ing and ah-ing in your speech; at your age a certain amount of it is cute, but too much suggests that the rest of the vid will lack confidence and thus also lack deliberate focus and/or artistic style.
- your vid does lack focus. You should have decided what you wanted to show us most - is 'the star' you, your gun, or the damage. Is the point you being cool for having the gun / shooting the gun, your skill at shooting the gun as demonstrated by accuracy at that range, the implicit arrogance in destroying something which cost a not inconsiderable sum of money, making the best of a bad situation (ie it's fucked, yes i'm a dick, but at least it'll be interesting to watch it getting totally fucked), comedy, something else? You see 'the star' of your vid as produced is the sh!t camera.
- your vid also lacks artistic style. Basically you've had an idea and put it in front of a camera and let the chips fall where they may. It doesn't communicate anything about your soul.
- the fewer the ideas to communicate, the shorter the better.
- destruction is a 'sharp' thing, so sharp dialogue, snappy edits, and a punchy style, is the way to go.
Finally, an interesting title will get more audience than just a description of what it is.
*See what I did there? By that writing style, I've drawn your attention to the fact that a person who is different to you, with whom you may well share little in the way of taste, style, or interest, is doing the communicating, rather than engaging your interest in what I'm actually saying. Did I engage your interest in what I was about to say? No. Thus: know your audience and speak to them in language with which they are familiar, which includes the style of video.
