Sewdhull

The only corrosion that's blue I know of is that of copper. But it could be ground up thread lock

You need 800+Celcius to anneal springs, stainless is higher. The 20FPS loss is because the spring is less pre compressed, there's no extra friction in having 1 bearing instead of 2. I'm going to explain why because it's come up before. If you compress a spring one end will rotate with respect to the other and if you have a bearing at one end, that end will rotate freely because bearings have less friction than the spring rubbing against another flat surface and once the bearing is rotating there is not enough force to rotate at the other end. The whole spring is not rotating, the wire is repositioning itself as it is put in torsion, so if it is fixed at one end the other rotates. In Airsoft we have bearings not for friction issues, but so that the spring maintains its shape and does not bend to one side or the other when it gets compressed. You could fix the spring at both ends and have no frictional losses but you would still have the spring deforming as it compresses. If you put a bearing at both ends and lets say, one bearing is a bit stiffer than the other, then the bearing with the least friction will rotate first, but the other bearing will not rotate because the force to rotate it never gets high enough since it is relieved by the first bearing to rotate. This is essentially what happens if you have just one bearing. Remember that if the spring is fixed at one end there are no frictional losses, as it doesn't move. Friction also doesn't care about area, only the force and coefficient of friction. So if you have a bearing at both ends the friction is double that of one bearing, since the force at both ends of the spring is the same. If only one bearing rotates, the friction is halved. Because the angle the spring rotates is double with 1 bearing the same amount of losses occur. Both bearings need to rotate of course for this to be true.

312 xt95 324 xt100 356 Xt105 That was on the MP5 and I lost just under 20FPS going to one bearing from 2 so they would be a bit higher with the 2 bearings. Progressive springs are designed to have the coils close up and (they would not be progressive if they did not) you will end up with a spring that wants to bend in the middle if you heat up the middle of it to remove the springiness. If you really want to shorten a spring don't cut any off, pop it in a cup of water leaving the 15mm( or whatever you want to shorten the spring by) poking out and heat up the end with a propane o butane torch nice and quickly to a cherry red colour. Let it cool in the air. Then compress it on a long bolt to shorten it. You can repeat the process if you need to. I've never really understood why people cut the spring at all.

Ultimately the thing that determines the strength of the spring is the force needed to compress it when installed and compressed in the cylinder. You can have a long weak spring that gets pre compressed on installation and will be the same rating as a short strong spring which gets pre compressed less. They are all of similar length with variations of up to 25mm from those I have. Then that option is not available to you. It's not the length that matters but how it's used. I bought a selection of AKs springs when I was trying to get the right fps on the MP5

Do you have a bearing on the cylinder head? If so you don't need the one on the spring guide. I cant recall how much i lost, ill go hunt down the post

A certain rated spring takes into account the length of the spring to arrive at the strength the spring will be used at. For example you can increase the strength of a spring using spacers to pre-compress it or it can be longer than another spring with same spring constant which ends up pre compressing it when installed. In fact all the springs seems to have a degree of pre compression when installed. For springs that are the same length they need to be stiffer, thicker wire or some such. Looking at the springs I have what seems to happen is that some springs are just longer than an otherwise identical spring, until you need to use a stiffer material because you'll run out of room to compress it. Springs are cheap enough, I wouldn't bother cutting one. Take off a bearing at the guide end if you have one on the cylinder head perhaps, you don't need 2 bearings.

Are all those bearings the same width? I use some 3x8x3 bearings and they do protrude and the one under the selector plate needed the plate relieving, but yours look wrong. One flush and one not is weird. i think you'll need to open it up again... https://simplybearings.co.uk/shop/Bearings-Deep-Groove-Ball-Bearings/c3_11/index.html?selection=Flanged+Ball+Bearing Select 3mm ID and you'll see 2, 2.5, 3 and 4mm widths.

LOL, it's not weight, it's mass. Then yes, 2k extra for you. Altho the hop works to counter the weight of the BB so i guess either would work...

The reason is that the average speed of the bb is higher if it is heavier. With greater mass the bb slows down more slowly and the force due to drag is less because of the reduced speed from the outset. So you have less deceleration all the time for the same speed (.2 vs .4 is half of the deceleration due to drag of the .2) and more drag for the same energy for the .2, because its going faster and drag is exponentially increased with speed. The result is that the .2 has a high force slowing a light bb which reduces it's speed much more than the lower force on a heavier bb. The heavy one overtakes the light one in effect and arrives sooner than the light one. The graph above from the Airsoft trajectory project shows the time and mass relationship.

Yeah time to target will be less with a heavier BB. Clearly at first, 15 to 20m if I recall correctly, the lighter BB will arrive first but the amount of time you are looking at is neglible. Only once the distance increases does time difference become a factor and then in favour of the heavier BB. Range is dictated by the hops ability to spin the BB and this uses energy so if you keep the same spring etc and try to spin a heavier BB you will lose some FPS but not necessarily any range, but you might.

A heavier BB will go further and quicker than a lighter one if it has the same forwards energy. The issue comes when you add hop to impart more of the springs energy to the BB to make it spin in a similar way to a lighter BB which leaves less energy to make it go forward, so it's slower out of the barrel not only because it's heavier, but also because some of the pushing energy got used up getting it to spin. Normally we would adjust the spring to add some FPS to compensate for the hop rubbing more. Joule creep happens because a heavier BB takes longer to speed up and exit the barrel than a lighter BB so the force acting on the BB can do so for a longer time (potentially the pressure will be higher too). This only works if the lighter BB wouldn't have used all the energy.

Sorry I thought I'd linked. https://www.ak2m4.co.uk/internal-parts/gearbox-tools

I think your chrono is telling fibs. Even if you didn't suffer from mech issues, your still going need a motor with a no load speed north of 60k

You should get a couple of clips for the trigger and ARL. Makes a significant positive difference to putting the gearbox back together.

Try using a 7.4v lipo.