Observations on ἱλασμὸν σωτηρίας

“[Soul-]saving forgiveness [of sins]” (ἱλασμὸν σωτηρίας).  This phrase does not make good sense in English:  “the pardon of salvation,” “the propitiation of salvation” etc. 
First, we must settle the definition of ἱ­λα­σμός.  Throughout the hymns ancient and modern, ἱλασμὸν ἁμαρτιῶν (which looks as if it is based on 1 John 4.10), ἱλασμὸν τῶν πταισμάτων and ἱλασμὸν ἐπταικότων appear regularly.  We note in particular that St. John of Damascus uses such expressions as πταισμάτων ἱλασμόν, πλημμελημάτων ἱλασμόν, ἱλασμὸν καὶ ἄφεσιν τῶν πταισμάτων in his Theotokarion.  We read also in the Triodion (canon 1, ode 9 of Monday of Cheesefare) that the fast is εἰς ἁμαρτημάτων ἀποτροπάς καὶ ἱλασμὸν σωτήριον, where the parallelism cinches our conclusion that the hymnographers seem to regard ἱλασμόν as a synonym for ἄφεσις.
How does ἱλασμὸν σωτηρίας fit together?  The crucial fact is that ἱλασμὸν καὶ σωτηρίαν καὶ μέγα ἔλεος is a common collocation in the hymns of the church.  No monastic hymnographer can escape seeing this collocation on a regular basis in the cycles of the services, particularly in the Menaion. 
This collocation can be broken up:  we find in the hymns ἱλασμὸν καὶ θεῖον ἔλεος and ἱλασμὸν καὶ σωτηρίαν.  E.g., St. Gerasimos also writes ἱλασμὸν τὸν σωτήριον, Παύλου τοῖς λόγοις ὡς ἐκομίσω (“when you received the salvific forgiveness by the words of Paul”) (St. Lydia of Philippi [May 20]).  
We can therefore suppose that ἱλασμὸν σωτηρίας and ἱλασμὸν τὸν σωτήριον are intended as poetic renderings of ἱλασμὸν καὶ σωτηρίαν.  The exact construction of ἱλασμὸν σωτηρίας I take in Wallace’s framework as an attributive genitive, which masks the attributive adjective as a genitive complement.  Apparently St. Gerasimos regarded ἱλασμὸν καὶ σωτηρίαν as hendiadys.