Dennis,
I think length wasn't critical so this is jus the length they came out at. Why more than one should come out at the 1/4" I don't know though.
When I made mine, I had to measure it afterwards, as length wasn't a priority. (43" actually)
Maybe he left the extra 1/4" for dressing the muzzle If it Needed it, and if it didn't, then we get 1/4" more for our money. :-)