doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Action stressing and elongation

Several past posts refer to action elongation resulting from overstressing as a possible cause for loosening in doubles.

Is there any reference to measureable action elongation?

The reason I am asking is a Beretta 682 someone showed me recently. The lockup is tight, the overall condition is good. But, there is a gap, big enough to put a sheet of printer paper through, between the top barrel and the breech face.

The trunnions are sound, the shoulders tight, and that leads to the thought of how the gap developed.

Other than action elongation I speculate that perhaps the chambers were stressed (Poisson effect) and took a permanent "set" making them shorter and fatter. Or that someone polished off the breed ends of the barrels, though there is no visible evidence of this. The breech face has imprints of the top barrels, so at some point there was contact with the breech face.

While pondering the cause another thought crossed my mind, do autos and pumps ever show loosening of their lockup? I have never seen one, yet.

If it "locks up" well but you can see through the breech it is well worth checking to see if the barrel wings are hard down on the action .There should be a clearance of at least .001" between. This is a common problem with many O/Us and when the clearance is achieved the barrels may come down on the face but need a lager bolt to lock up.

If it "locks up" well but you can see through the breech it is well worth checking to see if the barrel wings are hard down on the action .There should be a clearance of at least .001" between. This is a common problem with many O/Us and when the clearance is achieved the barrels may come down on the face but need a lager bolt to lock up.