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-   -   Velocity adjustments. An odd problem (http://www.mcarterbrown.com/forums/wgp/10006-velocity-adjustments-odd-problem.html)

Railgun 01-26-2007 03:14 AM

Velocity adjustments. An odd problem
 
I just finished coming in from playing with my new chrono. On my new WGP Sniper II I fired off a set and it read 160. That's fine, I cranked the IVG in about 3 turns. Now it was 380. OK, split the differnce... 370?!?! OK, back it off a bit more... 360. Geez, it's almost back where I started. OK, so split the difference again.... 360. Another 1/2 turn out.... 340. Almost there. 1/2 a turn out more... 160.... ??????????? The IVG needs to be virtually right out at the end of the body's rear opening or it's shooting hot

Setup on this is that it's using direct fed CO2 on a fairly new marker. So I'm guessing that the valve is actually set up for medium pressures and not the high CO2 pressure. I sort of expected some issues but this is crazy. Do I need a smaller diameter valve that is suited to CO2?

Now so far I've only chrono'ed blowbacks before but this seems rather odd to me. It's like with ANY pressure on the hammer spring it shoots up by a crazy amount and I have to back it off until the IVG doesn't put any pressure on it at all.

DarkNinja 01-26-2007 03:38 AM

Get a lighter spring.

russc 01-26-2007 05:47 AM

Sounds like you need a slightly weaker mainspring of the same length, or need to get a harder valve spring.

Eli 01-26-2007 05:55 AM

Or run a regulator....

Wycke 01-26-2007 08:21 AM

Quote:

Originally Posted by Eli (Post 89072)
Or run a regulator....

Werd. Newer WGP guns are not designed to handle unregulated CO2. What's happening is that with the IVG at it's "lowest" (furthest out) setting, the pressure in the valve chamber is preventing the valve from opening enough. There's sort of a "breaking point" at which the weight of the mainspring will overcome the pressure in the chamber, but then it's also overcoming the valvespring, so you've got too much gas flowing through the valve. You can try swapping around springs to find the right combination or use a regulator to bring the input down to around 400 PSI, which is what stock WGP valves & springs are really designed to work with.

doicomehereoften 01-26-2007 10:24 AM

Since it is a Sniper II, I would recommend a beefier valve spring. It'll help get the right balance in addition to hopefully helping against burping.

Railgun 01-26-2007 11:00 AM

I'm thinking valve spring in the light of the new day as well. I know that when it fires with no gas that it's really got a wussy hit on the valve pin. Unlike my direct CO2 Piranha blowbacks where the valve spring is a lot harder. Not to mention the super hard springs in the Nelsons.

I've got an autococker spring kit. I'll look into swapping the valve spring to a harder one as a first step. The hammer spring already seems fairly soft when cocking it so I'd almost prefer not to make it any weaker.


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