Just picked up a new airsoft gun (I know, no airsoft in this forum, but this is more about the cartridges than the gun) a Modify PP-2000 GBB. I had 2 JT brand cartridges left over. Both worked fine, would typically get about 60 shots per cartridge. Then went down to Walmart to get some more. All they had were the 5 packs of Crossman. Grabbed 4 of them.

The first pack I tried, all were duds. The second pack I tried 1 worked fine. Haven't bothered with the rest. The duds all seemed like they were almost empty. You would get 2 or 3 kinda weak shots, then the next time you pull the trigger, the hammer drops and just vents the rest of the gas from the barrel. But the venting was kinda weak compared to other times when a valve would stick on my other guns and dump a full cartridge. I checked the gun over and everything seems to seal up fine. The cartridges that work seem to work beautifully, so it kinda rules out problems with the gun or mags.

So I figured maybe Crossman is just crap. Went and got some more of the JT cartridges and a pack of Gamo cartridges just to try. Similar results. All the Gamos were pretty much empty. JTs were the best but would still get half duds.

So this just has me confused. The fact that it's different brands of CO2 all doing this would suggest it's an issue with the gun. But like I said, when you get a cartridge that works, the gun runs with no problems. And I have alot of experience tinkering with these gas guns. I can typically tell what's causing a problem when I see one. And this is giving me "not enough gas in the cartridges" vibes.

Anyone else notice alot of duds when buying 12g CO2 cartridges lately?

Try putting a drop of oil on the end of the C02 that get pierced.
Also make sure the cartridge is properly seated prior to tightening.

If you have an accurate scale, does a good full one way more than the bad batch prior to piercing it?

This is what I was wondering. And yeah a drop of oil helps seal the cartridge.

I use the Swoosh cartridges for blowing out drain lines in furnaces, I have NEVER gotten a bad one in the decade or so I've been using them.

I had an empty 12 gram Crosman cartridge that came out of a 40 pack but so far it's been 1 in about 80 cartridges.

Don't know how it is anymore, but back in the day the Leland 12 gram cartridges were the absolute best. They always gave more shots then the Crosman ones. Started researching the topic many years ago when in a 50 pack that i got from amazon when i bought a Crosman 3576 had a bunch of duds and underfilled cartridges. Only time it happened to me so i went searching. Unfortunately it seems like they aren't really made much anymore.