A week after Bendigo and Adelaide Bank completed an issue of residential mortgage-backed securities at the best pricing the market has seen in two years, Westpac has gone one better. The bank has priced the top tranche of its latest RMBS issue at 85 basis points over the bank bill swap rate and upsized the deal three-fold.On Friday, Westpac priced the Series 2013-1 WST Trust. The A$1.9 billion class A tranche, with a weighted average life of three years, was priced at 85 basis pointed over the one-month bank bill swap rate.Pricing on the $71 million class B tranche and the $97 class C tranche was not disclosed.Westpac launched the deal earlier in the week seeking $750 million, but it ended up issuing $2.1 billion.The top tranche of Bendigo and Adelaide bank's issue, Torrens Series 2013-1, was priced at 95 basis points over the one-month bank bill swap rate. The $790 million tranche has a weighted average life of 3.6 years.Compared with these deals, issuers were paying between 135 and 145 bps over swap to get RMBS deals away late last year.In August, Firstmac paid 165 bps over the swap rate on the top tranche of its 1-2012 RMBS Issue - almost double Westpac's pricing.Westpac Institutional Bank was the arranger and sole lead manager for the Westpac transaction.Talk is circulating that specialist lender Columbus Capital is undertaking preliminary marketing of a $500 million mortgage-backed bond. Columbus last tapped the market in 2007 and again in 2008.