Nothing inherently wrong in the math, just in the model you are using. As it turns out, Greg Nuckols just published an article on Muscle Math, which sheds some light on why it is simply not feasible in practice to go from 300x3 to 840 lbs in 1 year (52 weeks).
Some of the major take-aways are:
- Recovery activities have a power law distribution (i.e. the law of diminishing returns), which means there's a practical limit to how much food and sleep you can use to recover from the work.
- Training stress is like a parabola, up to a certain training volume and you will get stronger. Over that training volume you will get weaker.
- Newbies and early intermediates have a high parabola that is narrower. This means you get more benefit from every training session, but you can't do as much as an advanced trainee.
- Late intermediate and advanced lifters have a flatter and wider parabola. This means you can do a whole lot more work, which is necessary to getting stronger, but the overall benefit to that work goes down.
He has some practical applications to this muscle math, but it will at least help you understand that the path to getting stronger is not linear. In fact, I'm not aware of any biological processes that are. It definitely feels like you could keep going right now, but don't be surprised when your progress slows down. All you need at that point is a different way to manage your training volume and intensity.
You should also consider that the number of people who can hit an 840 lb raw squat (i.e. no squat suit) are very few.
Transitioning from Beginner to Intermediate and Beyond
First, I'd like to recommend not worrying about whether you are advanced or intermediate. The whole concept of classifying yourself either by someone's strength standards or by your recovery rates (a bit more accurate) is a bit arbitrary. You can draw the line anywhere you want, and that's really not the point. The point is really what do you do when you can no longer PR every week?
This is where we have to introduce the concept of periodization. Put simply, periodization is the way you organize your training over the long term. You will be getting to a point where increasing weight will be increasingly difficult for a few reasons:
- You start feeling like you are in a fog all the time, and you start dreading going into the gym.
- Where exactly that happens is a bit different for everyone.
- You get to a point where you are no longer building strength, but merely demonstrating what you attained so far.
- The most assured way to build strength is to increase the volume of work.
Looking back at the muscle math article, you'll notice that there are units of work that are needed to build strength and as you get stronger you need to perform more units of work to get stronger. That's a good way to think about it. Essentially, you have to arrange the work you do so that you can increase the volume over time. This is where we get into the Texas Method (an intermediate program) concepts of a volume day, a light day, and a heavy day. The volume day builds strength, the light day provides active recovery while keeping the movement patterns fresh, and the heavy day lets you set a new PR.
The periodization article provides a number of tools to balance the demands of recovery, building strength, and demonstrating strength. You'll find that people with an 840 lb squat or better can't do that every day in the gym. They have to work up to it over the period of several weeks as they prepare for a competition.
The good news is that you can introduce these tools a little at a time. For example, if you are increasing the weight every time you squat, you can transition to the Texas Method approach to squat three times a week, but still PR at the end of the week. When weekly progress isn't happening any more, you simply use the same concepts and work on increasing your PRs at a slightly slower rate.
The point is there is nothing wrong with slowing down, and it will be very necessary after a while. I personally didn't pick up a barbell until I was 39. Linear progression on the squats lasted until I could do about 310 lbs. Weekly progression got me to 325 for a triple. I then went to a monthly program, felt a whole lot better and got over 400 lbs squat before I turned 40. Due to some life events and injury, over the next couple years I was only able to increase the squat to 450 (no belt, in a competition).
Every person's journey is different. You may surpass my squat in the same amount of time (particularly if you are fairly young). The point is to find a way that you enjoy training, and continue getting stronger. Use the tips in the two articles I linked to, or use someone's out of the box program. Just put int the work and enjoy the process. An 840 squat takes years--on the order of over a decade.