The Loch class frigates were developments of the earlier Rivers, and were the ultimate escort frigates, drawing on experience from 3 years of U-boat hunting. They were built as prefabricated parts, with rounds replaced by squares and curves by straights to facilitate production, these sections welded or rivetted together depending on the builder's facilities. Like the other escorts, they followed mercantile building practices, to speed building.
The two major advances were the excellent SW type 277 RDF ad the squid, a 12" mortar capable of lobbing a depth charge for 1/2 a mile. Unlike squid, this exploded at a set depth and not on impact, so was far more effective. Such was the confidence on this weapon, depth charge stowage fell from 200 in the River class to one rack for 15 on a bare quarterdeck.
The main dvantage of the Squid ( and Hedgehog to a lesser degree ) was that on a final run in to depth charge a target, the asdic became inoperable - the ship was blind at the vital moment. Thus, a weapon with a 600 yard range could range-out whilst still in asdic contact, for an accurate attack. These were regarded as the main weapon, unlike the River class in which the gun was the main weapon, the DC's being there to bring up a submerged target. The two squids were hosed in a protective housing on the shelter deck, dry, safe and with a direct supply of reloads. The 4" gun was relegated to the forecastle in a characteristically tall HA mount. A multiple pom-pom replaced the 4" gun aft, and there was provision for two tin and up to eight single 20mm cannons, although only 2 tended to be carried, or two 40mm Bofors.
The heavier SW type 277 RDF required a lattice foremast, the set at it's head, and IFF 242/252/253 was carried to complete the setup. Two asdics were carried; depth finding and a range / search / attack type.
Two vessels carried turbines to investigate how suitable they were, but it was obviously impossible to fit a large number of the class with them.