Airsoft Canada - View Single Post - Weird upgrade result

Karhgath · July 18th, 2007, 20:48

First time upgrading a gun, followed mechbox.com videos and tips and tricks around this site, had no problem (I'm pretty good at those things). It's an ICS MP5A4. (V2 mechbox, 100% tm compatible as I found out, not the split one) I also kept the stock barrel (no longer/tighter barrel)

First time I opened it, it already had metal bushing and a minor spring upgrade (MS110SP I was told), rest was stock. I didn't chrony it as I had no chrony at that time, but it was supposed to be about 320-330.

So I put in a MS110SP spring, metal bearing spring guide (guarder), air nozzle, and Angel silent piston head/cylinder head. By my calculation, it should shoot at around 360-370 (the angel set should cancel out the spring guide gain).

Went to a game and it was shooting at 290!! Weird...

Then, the gun failed, I though I had stripped something (but wasn't the case as I found out). I bought a chrony and went testing with new gears (guarder), piston (systema) and a MS120SP spring. That should logically set me above 400. Just finished the upgrade, gun seems to shot a lot harder, but I chrony it at... 320-330. This is consistant compared to the previous 290 tho, but no where near what's expected.

What could be the problem of such low but systematic FPS? Gear timing is perfect, shimming looks right, the shot is really consistant. Could it be the cylinder (the only stock part now) that I should change for one made for a longuer barrel(m4)? Maybe the spring is too strong/fast to compress properly with the mp5 cylinder?

I don't know, I'm all out of ideas. The chrony works fine, tested with other guns with known FPS and it reads fine. I'm also using high quality .20.

July 18th, 2007, 20:48	#1
Karhgath Trader rating Join Date: May 2006 Location: Montreal	Weird upgrade result - Low fps First time upgrading a gun, followed mechbox.com videos and tips and tricks around this site, had no problem (I'm pretty good at those things). It's an ICS MP5A4. (V2 mechbox, 100% tm compatible as I found out, not the split one) I also kept the stock barrel (no longer/tighter barrel) First time I opened it, it already had metal bushing and a minor spring upgrade (MS110SP I was told), rest was stock. I didn't chrony it as I had no chrony at that time, but it was supposed to be about 320-330. So I put in a MS110SP spring, metal bearing spring guide (guarder), air nozzle, and Angel silent piston head/cylinder head. By my calculation, it should shoot at around 360-370 (the angel set should cancel out the spring guide gain). Went to a game and it was shooting at 290!! Weird... Then, the gun failed, I though I had stripped something (but wasn't the case as I found out). I bought a chrony and went testing with new gears (guarder), piston (systema) and a MS120SP spring. That should logically set me above 400. Just finished the upgrade, gun seems to shot a lot harder, but I chrony it at... 320-330. This is consistant compared to the previous 290 tho, but no where near what's expected. What could be the problem of such low but systematic FPS? Gear timing is perfect, shimming looks right, the shot is really consistant. Could it be the cylinder (the only stock part now) that I should change for one made for a longuer barrel(m4)? Maybe the spring is too strong/fast to compress properly with the mp5 cylinder? I don't know, I'm all out of ideas. The chrony works fine, tested with other guns with known FPS and it reads fine. I'm also using high quality .20.