Steyr and slugs? Steyr Barrel Maker?

In case anyone else wonders about the results of slugs in the Steyr:

I tested the 21 grain NSA slugs against my guns preferred pellets (JSB Monster Redesigned and Air Arms Field) and the slugs didn't do as well at 30 yards. They did better than many of the pellets I've tested, though. I believe the diameter of the slugs is just a tad too small as they just fall into the magazine. The chronograph of each magazine showed the first shot with the slugs being about 30 fps faster than the remaining 4 shots. This tells me that the slugs are not indexing through the magazine properly. I've found that the Monsters and Air Arms pellets need a little effort to be pushed into the magazines. I think it is the slightly larger head size that makes them more accurate in my gun than other pellets. Here is a comparision of group sizes of the slugs compared to the JSB Monster Redesigned: