After inserting and compressing the CO2 cartridge, the CO2 leaks

you will have to send it back to the manufacturer to get repaired.

The crosman 1008 does indeed fire pellets! NOT BBs. ONLY pellets.

Your seal is probably out...

I have the same problem and have dealt with guns for 40 years !
I am glad to see that the other folks have some realistic and innovative ideas of how to remedy this problem.
I went to Lowe\'s on a "tip" and found some very small \'O\' Rings for $ 0.87 for two and I am experimenting with them. The first try I couldn\'t crank the screw down far enough to even puncture the CO2 Cartidge. Using a larger screwdriver I finally managed to puncture the cartidge, unfortunately it still leaked but waas a much smaller leak.

Still experimenting.

I am going on-line to locate the Model 380 Schematic diagram which is where I ran int this site.

Good luck all !

The Phantom Break-Barrel does not use CO2. It is a spring-loaded break-barrel weapon. If you really do have a CO2 gun, check the rubber seal around the outside of the cartridge puncture needle.

Probably not by you, but by the shop, maybe. It sounds like the needle was bent and lost it's seal. Crosman has repair stations, if they don't fix it, they will send you another one. I have sent them guns before and got brand new ones instead of the old piece of junk I sent them for repair. They also bought out Sheridan/ Benjamin line of Air rifles, And they repair all those too. I sent them an ancient rifle, an old Benjamin Franklin,17 cal. bare bones stock and barrel only, they sent me back a total refurbish, welded, painted, new .22 cal.barrel, all new guts, unbelievable. I think the total cost was $35 on that one. They wanted $15 for paint, I told them I didn't want it painted, they said, OK, Get a hold of them. Hope this helps.

Well that takes me back! I have an old Daisy 1200 -- essentially the same pistol in a different brand.

My Daisy has a hand-turn screw to hold the CO2 cartridge in place, and you have to tighten it quickly until the leaking stops. It does this by pressing the cartridge up against a nylon washer to form a seal (and of course pushing it into the piercing pin to get the CO2 out!)

With age, I'd expect that nylon washer to get stiff or crack, making it harder to form a good seal. You don't need an exact replacement part, but if that's happened to yours then you will need to replace it with something more-or-less the same size as the original.

I would send it of to fix, playing with compressed gas is dangerous, sound like a seal my have corroded.

This is better known as a Crossman Air Pistol and it is powered by co2 cartridges that will not last too long once puntured/installed in the pistol, they tend to leak out within less then a day if not being used so try to use the cartridge once you have it in place.
Some fire BB's and some fire pellets.
Wear protective eye wear and clothing and always fire down range never point any pistol at anyone when handling it keep your fingers off the trigger and point up or down range.
Happy Target Practicing!!

Frank i would love to help you, i'm an airgun enthusiast too. please tell me the model crosman you're shooting at the moment and i would love to walk you through this, if you need repairs i'll also try to help get you in touch with parts or some ideas for service if it's needed.