Hitting at multiple distances is different for each style of throwing, whether it is "spin", "no spin" or "instinctive".
On knife lengths, first, I am assuming you mean blade length not overall (OA) length, as a 4 inch OA knife would be rather difficult to control under any circumstances. All lengths I reference are OA. I never throw anything less than 12 inches OA and 12 ounces - the old "ounce per inch" rule. This is a safety rule out into place in many competitions to reduce severe bounce backs. Lighter, and smaller, knives tend to bounce back towards the thrower much more easily than larger, heavier knives. IKTHOF has modified their rules since incorporating the no-spin community into our ranks. I think the minimum for no-spin competition is 10.5 inches OA.
The following are MY interpretations of the terms -
Spin throwing - knife is held by the handle or the blade and thrown with 1/2 spin increments - 1/2 spin by blade, 1 spin by handle, 1-1/2 spin by blade, 2 spin by handle, etc. Each 1/2 spin increase moves the thrower back some distance "X". Under competition rules, a minimum distance is specified for each rotation amount. Under IKTHOF rules, 1/2 spin distance is a minimum 2 Meters, 1 spin is 3 M, 1-1/2 spins is 4 M, and on. 1/2 spin at 2M is the MINIMUM distance the thrower must stand when throwing. As an example here, for 1/2 spin, 2M is about 80 inches or 6 ft 8 inches. With my 13" knives, I stand at about 7 feet. With my 16" bowies, I stand a couple of inches further back.
No Spin - the knife does not spin any rotations from when the knife leaves the hand until the point hits the target butt. Some people have called this "1/4 spin" as TYPICALLY the knife is almost vertical as it leaves the hand and rotates from vertical to point forward. The distance from the target doesn't really matter. The throw is more or less the same at any distance. In reality though, there are subtle differences in the knife release at different distances, but they aren't "noted". This style has also been associated with the terms "military throwing" or "combat throwing". I dislike those terms because I don't consider them "true styles". But that's MY opinion.
Instinctive - the knife or tomahawk makes 1 spin from release to target regardless of distance. I know of throwers who can take the same knife or hawk at throw it from 6 feet to 30 or so feet, with the knife or hawk making a single spin. This, in my opinion is the most difficult method to master.
Some people use the term "instinctive" when they really mean "no-spin". I tend to think "no-spin" when I hear "instinctive" simply because so few people are adept at true instinctive throwing.
The following information is just MY ramblings. Others probably view throwing differently and will have their opinions.
Different length knives spin at different rates. They also have a different flight pattern when thrown "no-spin" style. The only way to successfully throw different length knives in either style is to practice extensively with various length knives until you develop a "feel" for each length. I am NOT a master thrower, NOT a trainer, etc. I WILL show someone how I do it, and tell them to give it a try. What I do is tell them to
"Pick a knife. Learn to throw THAT LENGTH OF KNIFE comfortably. Add a different length knife ONLY when comfortable."
For spin style, you learn to throw from a 1/2 spin distance. When you can consistently stick 1/2 spin, ADD your 1 spin distance. Keep working your distances out. Over time, you LEARN to innately learn to judge which end of the knife to grab when throwing. Example - You can change your 1 spin distance by subtlely changing how fast you cause the knife to spin. If you are 1 foot closer than your "standard" 1 spin distance, you "just" spin the knife a little faster than "normal" to get the point lined up a little quicker. I routinely practice at unknown distances, but i'm not good at it yet.
For "no-spin" training, start at about 6 or 7 feet. Throw "no-spin" repeatedly until you start sticking them. There's tons of youtube videos showing how to do it in "various styles" - Fedin, Thorn, "military", and more. Many more. I've been told "my style" is different from any of the "standard" no-spin styles. Probably because I just read about how to do it with no videos to watch (back then, dial-up wasn't really up to a lot of video downloads). My training style was as above - I started at 6 feet. I threw and threw and threw until I could stick 20 in a row at 6 feet. Then I moved back to 7 feet. AND repeat. Then to 8 feet. And on out. After about 15 feet, I still haven't gotten to 20 straight hits. I throw beyond that distance for competition training, but only so I don't totally get zeros at the 6M and 7M distances. I can hit out to about 25 feet, but not very consistently. Probably due to my knives. I throw the same 16" 19 ounce bowies for all styles. At long distances they fly like wounded ducks.
My no-spin training method is based on how I was told to learn how to throw "instinctive style". I figured if it would work for instinctive, it would work for no-spin.
As mentioned above, my recommendation is to start with 1 knife length and learn THAT length well. Then add another length. That said, for a 10" OA knife, 9" to 11" will rotate at a very similar rate and should not take long to assimilate. It all boils down to muscle memory. Lots and lots of practice.
