Since A1 parts aren't in production, CavArms wisely designed their A1-length stock to use common, widely-available A2 parts, except for the top screw where that wasn't possible.

-Troy

Another interesting thing we learned is that AR rear sling swivels are so expensive because they use a non-standard thread.  They are essentially the same as the sling swivels used on the M1 garand and use the same thread pitch.  We also had a hard time getting the different swivels for the M4 SOCOM stock.

So we had our own sling swivel stampings made that uses a standard thread pitch, and works with either stock.  We include these with all our C1 and M4 SOCOM buttstocks now as a courtesy to our dealers and end users.  Our sling swivels are big, beefy, and not entirely pretty, but they work.

The C1 stocks will still use a standard A2 swivel and screw, and the M4 SOCOM buttstocks use the same as the RRA ones.