It's hard enough feeding my K-31s with the price of 7.5x55. I could only imagine having to feed a semi-auto.
In addition to trying to attract the attention of the Foreign Military Market, SIG also attempted to attract the interest of civilian shooters. Two major variants were produced. The first, the PE57 is a semi-automatic version of the Stgw.57, chambered in 7.5x55. Nearly 4000 PE57s were produced. The second variant, the SIG AMT (American Match Target) was chambered for 7.62NATO, and around 3000 were imported. Included in that number is a small number number of 510-4s built on full auto receivers, but with semi-automatic internals. At the time, the BATF classified them them as semi-automatic weapons, and today they are likely to bring a premium price.
Like their predecessors, the Stgw.57 Series were machined to exacting specification. The Stgw.57 series is generally considered to be the finest select-fire rifle ever made for military serve. Workmanship, accuracy and reliability were unmatched. However, these qualities also made the Stgw.57 the most expensive production rifle of it's time.
Today, PE57s and SIG AMTs are quite rare, and consequently, quite expensive. Average price for either is around $3500.00. DSArms is currently selling PE57 and SIG AMT parts kits, and Tennesse Guns sells SIG AMT parts kits. However, in each instance, the receiver is missing. And, there is no known source for domestically made receivers, or U.S parts kits, to allow for the legal construction of the rifle from the kit.
The Stgw57 served with front line units until 1982, when it was replaced by the STG90. However, the Stgw57 is still popular amongst reservists, and continues to hold a place of honor in many Swiss households.
Both the 57's and the AMT's are fun to shoot! I am lucky enough to have fired BOTH. They were a friends who really had the money to support a GUN hobby. He also had 4 FN (Browning) FAL paras to go with them. I was lucky to have the money to feed them. 7.5 Swiss was REALLY expensive and hard to find then.