Sl 68 issue

[Tippster]

Recently bought a first gen SL 68, aired it up and it fired but I could hear a small leak coming from the rear. Disassembled it and replaced the two o-rings. Reassembled and had a leak down the barrel. Pushed the valve/valve seat back further and re installed the set screws, has no leaks but can hear air escaping when I open the breach, and occasionally fires multiple shot when pumping back. Thoughts?

[Toestr]

I'm first thought is that the input pressure is too low. If it fires when you're pumping back, the hammer is probably pushing back on the powertube when the bolt is latching.

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[Ironnerd]

Nelsons do like to misbehave when they get too low on pressure. They were designed to use 12g CO₂ Powerlets which deliver about 900 to 1,000 psi depending on temperature. Larger bottles (7 oz, 9 oz, 12 oz, etc...) have the same pressure versus temperature curve - CO₂ pressure in a partially filled container is completely dependent upon temperature. That's why I don't use my HPA tank with my Nelson markers.

Where this matters is that Nelsons need real pressure (PX) behind the cup seal for the system to work properly. With low PX, the hammer bumps the valve open a little before it latches to the bolt. That lets a puff of air into the chamber which pushes the ball in the breech forward into the barrel and allows a second ball to drop in form the hopper (although this can also happen if the barrel i.d. is too large and you tend to tip the muzzle down when cocking... so don't do that).

If you have good pressure, check the cup seal. If it looks nasty, it should probably be replaced.

[infamoussmiley]

Where can one buy a new cup seal and power tube for the SL 68?

Best,

Smiley

[Jonnydread]

I haven't ordered anything from them in the last couple years, but in recent history Tippmann still had spare parts and seals available for their older guns so it may be worth reaching out to them. Outside of that I think your only option would be here or Bacci.

[Chappy]

Tippmannaprts.com and pbsports.com both seem to be out,. PBSports bought out TPI's old stock years ago, so I would be very surprised if Tippmann USA still haev any, but it cant hurt to ask. Bacci and MCB are your likely best bets.

[Chuck E Ducky]

Sounds to me like a Cup seal issue unless your Pump arm is screwed out to far.