PTR steel lower question...

[Wolfsburg]

I'm thinking about buying a clipped and pinned steel lower for my PTR but from looking at the pics I've seen, I don't understand how the stock attaches to them. On the "Navy" style polymer lowers there are two holes for the two buttstock pins to go through, but the steel lowers don't seem to have these. How does this work? Do steel lowers require a special type of buttstock?

 

[Shear_stress]

The steel lower doesn't have the holes, but has a "tail" that goes inside and is retained by the sheetmetal portion of the stock.

 

[Wolfsburg]

Hmm, so is it only held on by friction? I guess I don't understand how the buttstock stays put without those pins holding it onto the lower.

 

[Shear_stress]

The lower goes on first. The stock then fits over the tail of the lower, pressing the lower tight against the receiver. The pins then go in, retaining the buttstock. The lower can't be removed without removing the pins and stock.

 

[Wolfsburg]

I guess I need to break the gun back down and look at how all that integrates together. I recently put a wood buttstock on the PTR and while the metal stock ferrule slips over the rear receiver and lower, the pins also seem to hold it tightly in place by going through another set of holes in the tail of the lower. Since the metal lowers don't seem to have these holes, what is keeping the stock secured, other than friction?