Actually the last 3 weeks I played one OTB game every week against 1800+ players in a local tournament, my otb rating was 1000 before the tournament(lost a lot of games in the chess club, average players of 1500+). The time control was 50 minutes each.Now my OTB rating is around 1250.

1. I was getting into inferior middlegames after the opening, this happened because they knew the lines better or better positional skills.
2. On tactical level they still blunder the same as an 1300 player. In two games I won the queen, first game by a combination of queen and knight and second game just pushing a pawn that blocked the queen after a queen check. My point is that these variations were easily sidestepped if the opponent took ten seconds analysing the position.
3. I won the first game by grinding out and eventually my opponent blundered, he didn't have a big advantage, only out of the opening but managed to equalise easy and before winning the queen also winning position. The second game I lost a piece in the opening by playing nervous and bad. We grinded some more but it was unholdable. Still I had some chances. The third game started with a little advantage out of the opening for black but a huge simple blunder in one made him gave up his queen, eventually it became two rooks and 3 pawns vs queen and 2 pawns. I blundered by playing too fast and lost a crucial pawn and resigned.
4. In all those games there were chances for both sides to win the game in the middlegame. The 1800+ players played better in the opening phase but not necessarily in the middle game. True probably 1800 players will win statistically more games against 1300 but I think the gap is smaller then you think.

1300s drop way more than 1800s

1800s drop way more than 2100s

Only till you get to 2200 and above, that most of the dropping stops, and many factors such as calculation, positional play, etc come into play.

That's from my experience so far though.

The majority of my games at last weekends National Open in Vegas, depended on a temporary pawn sac, or taking advantage of weak squares. 

I remember my days of playing in the C section at tournaments.  Invariably all the games hinged on one and two move tactics. 

I don't know about this generalization of 'magnitudes' all over in every area. I have played many 1800+ players and they were far from equally strong in all areas. I recall one, in particular, whose opening play was terrible: against any player much stronger than 1300 he was likely to come out of the opening worse off than his opponent, and consistently so.

It was tactics where he shined, and he also carried that and what looked like sound intution, into the endgame which he played well too.

Other 1800+ players were grinders: they seemed to shun tactical lines and complications completely, yet force you to play boldly or you eventualy simply got strangled. These were extremely patient players who tended to have good endgame technique.

I think around the 1800 range, there is enough tactical ability gained that whether or not the player goes for aggressive tactical play, or not, he has developed enough tactical skill that he will not be prey to the cheap shots 1300s consistently fall for.

But at 1800, there are no general magnitudes of all aspects of the game that is light years beyond anything. There is solid tactical play, combined with one or more elements of the game he has begun to develop some level of strength in - but is not the complete, well rounded player that the 2200+ crowd are. Note that one element may simply be psychological evolution, such as patience in quieter positions.

But who is generalising when you say "mainly tactics"?

You then even describe how other 1800's are not so tactical at all but have developed good patience and psychology.
Endgame technique is also not as much about pure brute calculation as it is about having experience, patience and recognising patterns.

That said it is also a matter of definition because if you look at it for example from a computeristic viewpoint you can simply say everything in chess is tactics and you would be right.
But from a human viewpoint and the way humans play we could make distinctions between different types of skills required.

Ofcourse an 1800 is not complete or light years ahead of anything.
Having been through the 1300- to 1800+ myself what's changed? Well..my ability to get good positions. How much of that is tactics? Some of it hardly all of it. Infact at 1300 I would try to play much more flashy thinking I was going to be the new Tal.. (And strangely I failed! ..for now  )

Its been repeated, time and time again, by highly regard chess authors and coaches that tactical study is the foundation for better chess play and a higher level of chess understanding. Examples:

'Chess is 99% tactics' - original author unremembered because its so often repeated  by other authors;

'Most games between lower rated are won, or could be won, on basic tactics' - Heisman;

'A positional advantage is of no use if you then fall into an elementary and decisive tactical blow' - Silman (that quote I'm paraphrasing).

From my own experience, and I'm only an improving intermediate player, but one who started below 1300 and has progressed some distance beyond it, it was tactical study that brought about the most immediate and substantial improvement in chess play. More recently, they have helped to cement positional concepts I studied years ago but could not integrate into my own play.

Tactics exist in the opening; in the middlegame; and in the endgame. Therefore its a logical deduction that proper study of tactics will carry over to all 3 phases of the game.

Today I try and balance my study between annotated games, some endgame study, a little bit of opening theory for incremental improvement in the major oppenings I play or face. But tactical study remains the backbone, and on the days where time permits study of only one element of the game, then tactics is the only element studied that day.

Q: what's the main difference between a 1300 and a 1800 player?

         A: The rating

And i am the flip side of that coin.  Tactics are the thing i study the least. 

I believe it was Tartakower that said the quote about chss being 99% tactics.  Joel Benjamin said chess is 100% calculation.  This is why chess study should involve all phaaes of the game.

I think when people mention tactics, they don't necessarily mean that just doing tactical puzzles mainly will bring one from 1300 to 1800. I think when people say this, they mean that being aware of the various tactical possibilities in a position is very important in improving. I think being aware of the various tactical problems that could occur with  strategic decisions is very important. Spassky in particular reproached himself for not always checking his ideas for tactical soundness. He claimed Capablanca was a genius in that he rarely ever made tactical mistakes. He, in fact, claimed that Rubinstein was a bad tactician in comparison.

I think this more generalized view of tactics and how they relate to planning is probably what people tend to mean when they say "mainly tactics."

1300 Player: Has some opening principle, but in middlegame is obviously outmatched tactically by an 1800 player. Endgame does not stand a chance.

1800 Player: Has an initial idea/execution in mind and calculates 4+ moves further throughout the game.

Okay I would agree with that. When I made my biggest jump in rating, it was while taking a pretty balanced approach to the game. On the tactical side, I studied the Art of the Checkmate, Winning Chess Tactics for Juniors, and Chess Tactics for the Tournament Player.

On endings, I read, and then re-read, Pandolfini's Endgame Course.

For middlegame/strategic Play, I read Chess Master versus Chess Amateur, How Not to Play Chess, Simple Chess, and Best Lessons of a Chess Coach.

The study method was to work through one book from each category together (so 3 at a time). It was my tactical play that looked to improve the most, but probably the other books played a role as well - just more subtle.

After a year of no chess, I spent a few days studying nothing but tactics, and in my correspondence games (the only play I've focused on since coming back to the game) it is tactics that have been the decisive factor.

But, because the break was due to illness that led to an abrupt stop in play, I forfeited enough games during that year to drop an 1800 rating to 1380. So when I began playing again, I got paired with under 1700 opponents and its been simple tactical blows that have decided most of them.

I have been 16 wins, 2 draws, no losses since resuming chess (one of them was objectively lost by me, but better endgame play converted it into a draw). I don't expect this streak to last long, nor would it exist at all were I paired with the same level of opponents that I was before the play gap.

I may give too much credit to tactics. I still use the three book system of study, so as to not neglect any aspect of the game, while my openings remain unchanged and I have many games with them that have built a level of comfort and familiarity that can only come with time and experience. And, lastly, positional concepts that I studied years ago have begun to crystalize more and find their strategic ideas into more of my games.

I still suffer the weaknesses that plague all intermediate players though: my ability to calculate is neither that deep nor consistent; I occasionally play moves consistent with "hope chess" where I've put too much emphasis on my own threats and plans, and not enough on my opponents; and there remain some serious gaps in my chess understanding. My evaluation and analysis skills, likewise, are inconsistent and not on par with stronger players.

It's really a matter of understanding what those 2 elo's represent. Like chess itself it's interesting what you can pull out just by making general observations. I wrote an indepth artice on this topic you might find interesting :) 

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Definitely. It is from where you will form your plan. I even think i have wrongly evaluated some important lines of our ongoing game too!

1800s do not drop pieces, or do so less often. Usually, they are much stronger in the endgame than 1300s, handle opening transpositions better, calculate deeper, and may have better emotional stability (i'm thinking of a particular 1300 in my local club who cannot bear being ahead a minor piece).

Were that true, the 1800 player would be devoting so much time to raw calculation that he would wind up in very serious time trouble early.

I suspect there are many 1800 players who either cannot do this (particularly in very complex positions where several threats are present), or simply are more pragmatic and choose not to - they have a solid enough grounding in tactics, strategy, and probably some basic endgame theory, to find good moves mainly by intuition that is derived from experience and the above abilities.

1800 is too intermediate a rating to make sweeping generalizations about that are supposed to apply to everyone in that rating class.

The more pertinent question: where is the 1800 player weakest? Any of Khmelnitsky's "Chess Exam" training books can answer that question.

Where is the 1300 rated player weakest? Everywhere. Any instructional book with rating appropriate annotation of games (Like Chernov's classic Logical Chess Move by Move), book on elementary tactics (Heisman's Back to Basics: Tactics; Hays' Winning Chess Tactics for Juniors; Alburt's Chess Tactics for the Tournament Player; or Polgar's Chess Tactics for Champions), or an approachable endgame book like Silman's Complete Endgame  Course, or the more elementary Pandolfini's Endgame Course, are all candidates.

Since the 1300 player is weak everywhere, its a reasonable conclusion to draw that by beginning his study with a well chosen book that addresses any of those weaknesses, improvement will come in time. Then he can broaden his scope of study to tackle another weak area, and so on.

Sounds good.

As your strength improves instinct, or intuition, still plays an important role. Its just that it gets better, more accurate, and you develop an intuitive feel for positions based on experience, analysis, study, or any combination of these.

It can guide you more successfully through the opening, aid in alerting you to tactical possibilities, and let you know when its time to simplify (and when not to) into a winning endgame where again intuition plays a role.

Its a popular misconception that the stronger your rating, the correspondingly better at calculation you are. We're not computers, nor are our brains wired like computers, so it doesn't work that way.

As far as calculation goes, I think it better to say that the higher your rating, the better you get at determining when its time to begin looking at combinations where accurate calculation is involved.

As an example, a weak player will look at a potential line of attack, but when he sees that the target is defended, he'll abandon the line and look for other moves. The stronger player will instead pose questions like "can I remove, decoy, or interfere with the defender?;" "can the threat of doing so create a weakness I can subsequently exploit, now or in the endgame;" and, most importantly "ok, it looks like this line will lose my Queen for a rook... but, looking deeper, I can then create a fork that wins the Q back and puts me up the exchange with a winning endgame."

Accurate calculation plays a role there, but its more than calculation. From my experience, my strength increased a notch when I stopped stopping the analysis the moment I saw a material deficit, like in the example above, where before it would end when I saw the loss of the Q. That leap in analysis had nothing to do with calculation ability or depth, but more of an intuition involving when to calculate, combined with the realization that calculation, if its worth doing at all, needs to go a move deeper than it used to before I dismiss the line.

I(a 1300 player ) played against Perseus82(a 1800) player.  If you're interested, here's how it went.

In this opening, after 9...a5, 10.Ba3! is the key move. As after axb4 Bxb4, c5 is threatened immediatly. (b6 a4! threatens a5) Gotta be fast, fast, fast in the Bayonette. Any move that saves time, do!

16.Ra1? was a tactical error.

Black could have won material with 16....e4. Luckily, you spottted that, and dodged it next move with 17.Ra2

Better was 16.Nc3. whenever black recaptures on f5 with the knight (instead of the pawn), he is giftwraping the e4 square for your knights. A knight on e4 in the KID is called a "Petrosian Knight." There it blockades the e5 pawn, locks in blacks DSB, and exerts pressure all over the entire board.

it is instructive to note how blacks Bg7 came to life, after 19...e4! In the KID, if black can find some way to make his DSB good, he often gets the advantage.

23.Na1? is bad. You still needed to blockaed that e-pawn, with Ne3. By lettting that pawn roam where it may, black can use it to generate vast quantities of counterplay.

Conclusion: You really have a good feel for the Bayonette. You stuck to your guns well, and attacked the queenside with fury. You just need to learn a few key ideas, to start killing 1800 KID players regularly.