L2 magazine for normal sized slugs?

I remember a whil back where Ed had shown a new mag for the L2 that would hold the standard sized slugs without them fallling out. Was this ever manufactured?
I know now that there are some companies selling L2 sized slugs, but I recently swapped to an FX barrel in mine, and while it shoots pellets great, I get some trouble shooting slugs. It seems like they might be getting damaged when the mag is cycling due to them moving in the mag. His is just a guess, I don’t see signs of lead build up on the lead of the barrel, but I did see a slight lead mark on the mag. I feel if we could pair a FX barrel with a standard size mag, the accuracy of this gun, along with a larger variety of projectiles, would be even better!
 
I don’t think the .303 slugs that avs, and Neilson make will work well in a superior liner. If I had an alpha barrel, it would be a no brainer, but the fx barrels I don’t think will work. Oddly enough, the .300 Neilson slugs had some fit the barrel OK and some fell through, so there are slight differences in diameter, but most other .300 slugs just fall right out.

Pellets work just fine, and have shown to be more accurate than the alpha barrels, but that mabe due to the alpha lacking a choke. Either way, I wish the mag was produced for us tinkerers that like to use different barrels in our toys!