Where did you get yours from...am thinking of getting a TAG setup. (I have a S&T M320 launcher that's doing nothing atm....)
i also have an S&T m203, but to fit the tag shells i have had to file off the ends of the ridges inside the barrel... (but it hasnt seemed to affect the ability of the launcher to use normal moscarts)
i bought a couple of CO2 TAG launcher shells from here:
https://www.airsoftworld.net/tag-innovation-co2-pro-evo-shell-launcher-single.html
if you buy the shells, DO NOT buy green gas shells, as with mk2 tag rounds, they may not ignite the fuses 100% of the time (advice given to me by a couple of people who regularly use TAGs) buy the CO2 (gold band) or HPA (red band) shells, and either a TAG FIST2 or TAG HPA adapter to fill them.
airsoftworld also stock the rounds, so you can get a full tag setup from the one shop...
https://www.airsoftworld.net/manufacturers/tag-innovation
the other option is to buy a TAG brand grenade launcher, so you dont need to buy the launcher shells (load a round in launcher and fire it using CO2 capsule).. downsides to that is that a TAG brand launcher is around £700... and you are restricted to ONLY firing tag rounds... so no using moscarts in general skirmishing, unlike you could do with the S&T launcher
Would the shell fit in a standard m203? Or too long?
depends on the barrel length, but a shell will easily fit inside a standard length m203 with room to spare.
i did have to file down the "ridges" inside the barrel of my S&T launcher to fit the shells into the breech, but its an easy job due to soft aluminium... just time consuming to fettle it just enough for the shell. having done that modification to my launcher, i have used it over a dozen times to fire moscarts without any issue, so no need to worry about ruining your launcher if you regularly use moscarts ?
can't find it for the life of me but yeah you need to cut a crescent shape on the underside of the m203 tube for it to fit in / ... fit out
i dont think you do.
with a round in the shell you will struggle to put the shell into the breech if you hold it parralel to the barrel, but if you hold the shell at an angle to put the tip inside the breech and then rock it in (like an AK mag) then there's no need for any cutouts on the barrel itself.
as i have said above, my S&T only needed the ridges inside the barrel to be filed down a bit at the breech end to allow the shell to sit forward enough to close the breech...