Say there is a hypothetical spring which has a free length of 10.0", and it requires a 10.0lbs force to compress it completely. If you cut that spring in half, it will still require 10.0lbs of force to compress that half completely. If the original spring required 4.0lbs of force to compress it 4.0", the half-length spring may also be able to compress 4.0", but that will take 8.0lbs of force. The spring did not become less stiff because you made it shorter. It can be confusing, I understand, but you have to be wary of nerf pages when you are trying to answer a physics question. There is a great deal of misinformation which has been disseminated through this hobby, and it becomes worse when people use the incorrect nomenclature.

Ok so from what I understand from your very helpful post, spring output is dependent on the free length and how much you compress it. The theoretical 5 inch spring took 8lbs to compress it to 4 inches since that was 4/5 of the spring. If you wanted to compress 4/5 of the original spring (by 8 inches), that'll require 8lbs. The constant for the original spring was 1lb/inch of compression. When you cut it in half, that doubled...

~~So now I'm going to try to apply that in my situation. The stock 6.5 inch Magnus spring took 4.5kg to compress it by 5.5in, that means it has a constant of 0.81kg/inch. I changed the full length to 4.5 inches. 4.5 is roughly 2/3rds of the original spring length. That means the constant increased by 1/3 (0.27), so the new constant is now 1.08kg/inch. Therefore, the new spring has an output of 4.32kg/inch?~~

~~I'm not sure this is right, so if I'm wrong, please correct me.~~

*EDIT:THE ORIGINAL SPRING ACTUALLY COMPRESSED TO 0.5IN*

HEHE, turns out I accidentally mismeasured the compressed length...whoops

So now I'm going to apply this to my situation.The stock 6.5 inch Magnus spring had to compress 6 inches, or 92% of the original spring. The new cut down spring is 4.75 inches long, and compresses by 4 inches; a.k.a 84%. It took 4.5kg to compress 92%, meaning 0.05kg per 1%. So to compress 84%, that'll require 4.2kg.

Does that mean that my Longshot has a 8.7kg springload?!

**EDIT #2**: Now that I think about it, I really don't think the stock LS spring is 4.5kg. The NIC Spring database records it as 2lbs per inch of compression. It compresses by 4 inches + the 0.75inch of precompression; that's 9.5lbs, or 4.3kg. Which means, my LS springload is really 8.5kg total.

But if we really want to get technical, the nerfwiki lists the Longshot's spring at 3kg?! Finally, OMW lists their 8kg spring as 2.5x the original?! Maybe if I have time, I'll make an updated spring database through all of my knowledge gained...

**Edited by Bubba Longshot, 02 August 2017 - 06:17 PM.**

"The only thing that sucks about Nerf modification is the anxiety that something will break... That's why we reinforce a whole lot!" -Me