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Oh my days 😁 you and your length obsession lol Is the spring you fitted one you purchased from me? If so you just grab the power just down from it. I'm away at the moment but can sort something out soon for you.

It's a number of variables, length yes but most important being number of coils and thickness of wire. And as @Sewdhull says it's the N force in the 60mm or so in the cylinder. Every gearbox is slightly different so you'll get some variation. 1.3mm vs 1.4mm thickness makes quite a difference. Also quality of wire. I went through 5 Chinese companies before realising they their grade of steel wasn't good enough and in the end switched to Japanese steel. Quite a long, painful and expensive process! I've had my tester M110 spring now for 4 years, must be 500,000 through it so maybe I'll do a video on it soon and compare it to the new ones. For some customers who are unsure what spring to buy I've been sending out my tester M100 spring, along with their order. That way they can benchmark with the M100 and then either keep or return. Just saves a few pennies for anyone strapped at the moment.

Looks to me like you've fitted a 3mm wide bearing under the selector plate but a 2.5mm on the bevel gear. Ideally you need 2.5mm bearings. You can fit 3mm, in fact EZO (3x8x3) get their extra strength from being 0.5mm wide. EZO do 2.5mm wide but the set I tested exploded. Can you measure them?

As @Lozart mentioned, I think your CORE model has a 460mm inner barrel as standard, presuming a full cylinder? (you'll need to check). If you move to something around 360mm then something like a 4/5 cylinder would be better. I just received a new stock of Outer Barrel parts, not sure how much the Laylax set is?

@EDcase The lettering on the CYMA Thompson looks amazing, am I right in thinking there was no need to paint? They look quite deep.

@Tactical Pith Helmet gas only days at the Mall were simply the best...

they're pretty decent for the price. Wish I could get hold of them easily though. CYMA are just super difficult to deal with for various reasons. @Ben Savage ZCI is decent, give another one a go and let us know how you get on. I'm started to list the widths (guide rail to guide rail) of all pistons now in the descriptions. Hopefully it helps a few people out.

Ahhh right must be their super budget range, CYMA really do squeeze out every cent. How much did you pay? Saw these for under £90 a while back. If it is the piston, might be worth picking up a CYMA piston, they're only around £8 I think. Only downside is they are 15 tooth as standard so you'll need to shave down if you want to do any AOE correction.

CYMA make pretty decent pistons, did the stock one have a full metal rack?

what one did you buy in the end? did you get some gauge blocks with it

there's a few here from SE London, which part? I spend some time in Sidcup and I believe Colin is not too far.

Yes I've got some arriving hopefully in a couple of weeks. I did have some 22tpa on a boat coming from China but the ship go round the long way 😞

pretty easy, you just need a few basic tools. Ideally something like a dremel / rotary tool, a pinion puller and vice. But you can get away with a hacksaw and a file. Whether you need a pinion puller depends on how tough the pinion is already on. Bit of threadlock for the grub screw.

@dlusted fantastic mate

@dlusted added, many thanks