Question about different velocities between single shot and auto

I put a nylon Warinterest box into a nylon Wells receiver, and am curious as to why it has such a difference in fps between semi and auto. The box is mainly stock, just added the usual $20 metal gears and 1.3 spring. Using the t-piece that came with the box (SLR I think) and gen8 mag. Stock Wells outer barrel, 350x9.5x7.5 inner. Stock Wells motor and grip.
I don’t think the nozzle (original) is sealing 100% into the t-piece when it fires, but it’s the big difference from semi to auto that has me curious.
Single shots (with the odd double gel balls shot) anywhere from200 to 215/220. Put it to auto, all around 260 to 280. Put a few magazines through it using Warinterest milkies sizing anywhere from 7.2 to 7.4mm.
Anyone have an idea why so much difference?

My guess would be that when it is at rest, the seal is just sitting in the groove… cycled once, the seal might not get a chance to sit properly… once cycling multiple times, the seal has no time to relax, it is either one side of the groove or the other.

Did you do the seal? Did you use lube if you did? :thinking:

Hey mate, thanks for the reply.

I presume you are talking about the piston head 0-ring seal? Not sure what you mean by “do the seal”.
The stock o-rings and cylinder had good compression, the stock nozzle not so good. Waiting for upgrades.
I really just put it together as it is to see what was involved getting it to work in the Wells receiver.
And yes, plenty of lube on the rings.

I have done a few Wells boxes with the Gelballmod kits and they have all ran well with consistent 280-300 fps. The only problem has been the plastic casing cracking in the usual spot-the front right corner. So I thought I’d try a nylon case. Someone on here did mention he’d heard of a reinforced or upgraded gearbox casing for the Wells coming out, but I’ve seen nothing yet.

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