Issuers of residential mortgage-backed securities are enjoying strong market conditions. On Friday, AMP Bank upsized its latest deal to A$1 billion from the A$500 million it was seeking at the launch, and priced it at tighter margins than its previous issue, last September.Heritage Bank also priced an issue on Friday, returning to the RMBS market for the first time since 2011 with a $400 million transaction.So far this year, Macquarie Bank and Bendigo and Adelaide Bank have been able to improve on the pricing of RMBS deals they did last year, with the margins on top tranches coming in by between five and 10 basis points. AMP Bank will pay 95 bps over the one-month bank bill swap rate on the $920 million A tranche of Progress 2014-1 Trust.Last September, AMP paid 100 bps over swap on the equivalent tranche of Progress 2013-1 Trust.In the latest deal, pricing on the $60 million AB tranche was 165 bps over swap, pricing on the $15 million B1 tranche was 245 bps over swap and pricing on the $5 million B2 tranche was 300 bps over swap.Heritage Bank will pay 95 bps over swap on the $368 million A tranche of HBS Trust 2014-1.Pricing on Heritage's $20 million AB tranche was 165 bps over swap. Pricing on the $12 million B tranche was not disclosed.