Will the kit have Zimm? Dan

Very true! At best they can add the front edge of the grooves as seen at the tip of the barrel, but the groves go straight back without a twist. To add a twist you need the sliding plug to "corkscrew" as the mould is pulled open, and I suspect that would easily double the cost of making the tool for that sprue...

I think that a PE inner sleeve for the gun is the cheapest and most practical way to make the rifling. But it could be difficult to bend it, because of course it will want to fold on the rifling lines instead of making a curve. I would provide a plastic guide to push it into. David

I used Aber`s PE upgrade set for the Tamiya Sturmtiger. I remember thinking to my self "well, this is impossible to fit inside", but somehow it worked carefully bending it to shape. However, as someone else said in this post, gap between plastic and the PE seemed to be inevitable. Not to mention that adding a sheet of PE inside the barrel will screw up the barrel diameter.

The kit could be designed so that its own PE brings the barrel to the correct diameter. Aftermarket PE won't do that. David

Does anyone have any info as to how the barrel attaches to the trunions in this kit? This area specifically:

This kit looks really impressive. I may just have to sell off my ancient Tamiya kit with the doodads I collected for it.

Or you could mold it two halfs with the rifling following the mold lines,

Then you'll have people complaining about the several generations ago molding technique used, and the accompanying joint seam to fill!