don't sweat it - think TWG know what they are doing
they might use a m90/95 or their "usual" spring they use to bring down hot guns
most of Europe run with lower limits than china guns out of box
just remember Guarder springs are good but just a tad warmer than we often think
SP100 does not mean M100 but perhaps more like a M110 spring the reports say
often most springs are a little tiny bit warmer new as they are only a rough guide and fade a smidge in use
The guide is quite rough as longer/shorter barrels effect the fps or creep
plus - total spring compression can be increased by spacers/bearings/spring guide
so the same spring in two guns/build "could" produce 300 to 360 fps (honest)
TWG downgraded it, the test sheet they included showed 336, 343, 348, 342, 344. They didn't use the SP100 or tightbore, I think they just cut down the existing spring, or as you say, put in their "usual" spring. Quite a lot of variation, so I don't think the spring quality was up to much.
Anyway, I sent it straight into the techies at Stevenage who've fitted the tightbore, the SP100 and with the hop up in it shoots bang on 350 (i think one test shot did 351 they said, but I'm not worried about that), and far more consistent - within 3fps. What I did notice however is that the rail system on the front is actually in 4 separate sections and there's a little bit of wobble (apart from that, the guns really solid), I think they've tightened that up too. Going to nip out and pick it up tomorrow, can't wait to shoot it for the first time!
Also impressed with the cheapo EOTech clone I bought with it. Razor sharp and crystal clear, came with both a screw type and quick release type mounting screw, the green setting is super bright. Doesn't glow up from the front either like some of them do. Feels rock solid.
Unfortunately, UPS gone screwed up and delivered 3 days late, so I missed the skirmish on Wednesday night which I was looking forward to. Night games are rare and lots of fun. Got to wait until the 16th until the next skirmish. Damn!