Thanks for that. This as me pondering how i could fit a side lever to my S410.

Would i be correct in assuming the S410sl only came in FAC power and as a S510 block also.
Seem to remember that it was a shrouded barrel also.

Interesting thread.

Could you not just fit a S510sl block in place of the S410 bolt block.

Though looking at the diagrams of the parts you may be able to just fit the side lever and probe to your S410.
But not having compared the 2 this would need confirming.