Twist rate. Std. 93 barrel twist rate is 305mm or about one full turn every 12.2 inches and usually are not marked with the numbers 305.
The number 178 means that the twist rate is one turn every 7.12 inches a much faster rate.
While I have seen Hk 53 barrels with the 305 twist rate, I believe the standard twist rate on an HK53 barrel is 178.
As to when the Hk53 entered the HK product line I think that is a question for Tony to chime in on.
I have ones with rivers and without
He had it listed starting at $3k and it had gone through several cycles of not selling. When I answered his question (from my original question to him), it changed immediately to $3,300.00 without any explanation. Total ass, but I am happy with the gun.
"The problem with socialism is eventually you run out of other people's money" ~ Margaret Thatcher
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