Brownells Gunsmith Tech Corner - September 2008

Question: I recently bought a 14 lbs. progressive recoil spring made by Sprinco (#943-102-014). How will I know if it is progressive recoil spring from a non-progressive recoil spring? Does the distance between loop of the spring vary? The package doesn’t say that is progressive recoil spring but after measuring the distance between loops, I found that they’re the same. Could you give me ideas about these? It would be of great help.

Answer: Progressive is just a term Sprinco uses to describe a high performance spring. It is not to be confused with a variable spring, which will have coils at different spacing. The Sprinco spring is a conventional style spring. If you prefer a variable spring we have one from Wolff (#969-424-014).
-- Steve Ostrem, Brownells Gun Tech



Question: Could tell me how a gunsmith would headspace a firearm that is fired from an open bolt?

Answer: Generally on an open bolt firearm the breech bolt closes completely (flush) on the breech face, and the case head of the cartridge is flush with the breech when it is in the chamber. With an unloaded gun, open and close the bolt on the breech face and note how the action closes, it should be observed to close flush on the breech. Next check the chamber with headspace gauges, drop the no go into the chamber, it should protrude above the breech slightly while the go gauge should be flush with the breech.
-- Eric Kiesler, Brownells Gun Tech