Well well... how springs settle...
Sepulcrum came over to my place tonight so he could chrony his HK416. He fired maybe a dozen or so shots thru the chrony using Metal Tech .20g (used my BBs), and his was firing pretty consistently at about 370 -380fps. With these low results compared to what I had shot with mine originally, I put about 25 rounds through my chrony with my 416.
It seems like my current muzzle velocity is somewhat lower than when I originally chronied it. Tonight it was shooting pretty consistently (for the most part) in the 410 range, with an odd spike or drop in velocity. About 5 or 6 shots in a row clocked exactly 410.7 (the screen blinked before the new reading came up, so I know it wasn't just the chrony not registering the shots). A few subsequent shots also hit exactly 410.7. The high was a single shot that hit 435 or so and there wa couple of low ones in the 388-394 range. But it was pretty consistent in the 410-420 range for most shots.
So it would appear that my spring is starting to settle with a bit of use. I've only fired about 200 rounds out of it at most since I got it. When I first chronied it, I had put at most 50 rounds through it, IF that. Sepulcrum said he's fired over 600 out of his, and it was about on par with the advertised velocity of 370 for this gun. It appears that the stock springs might sette down somewhat with use. I'm hoping that happens with mine as well. I hope that it eventually settles down to a sub-400 fps speed like Sepulcrum's did.
This could also explain why my MP5 seems to shoot a lot lower velocity than when I first got it. I thought it was shooting mid-to-high 300s. After putting 1500+ rounds through it 2 weeks ago at a friend's house, it didn't seem to shoot quite as fast as it did before, although still hitting with respectable force. When I finally chronied got my chrony, it was actually shooting 340-ish. 10 fps above the advertised speed.
I'll keep an eye on this and chrony this gun more regularly as I shoot it to see if the springs settles, and if so, how much.
On another note, we opened up our guns and compared internals. He has the SB-tagged mechbox everyone else seems to have with these 416s. I have a UTG-tagged mechbox. However, from what we could tell without actually removing them from the gun is that they appeared to be identical in every way. The pistons, springs and spring guides all appeared to be the same. The finish on his spring was a bit worn since he's used it more than mine, but otherwise, all seemed the same. Even the SB and UTG fonts were the same, although the UTG tag is stamped deeper into the mechbox shell and in a slightly smaller size font.
And yeah, his rails are sharp too. He's worn down the edges on his top and bottom rails a bit, but hasn't done the side ones. Mine are sharper than his.