The Firing Line Forums - View Single Post - How do I know if I am crimping too tightly?

James K · March 23, 1999, 10:47 AM

Raymond and Walt,

Let's try this again. To be actually held back by the extractor, the case would have to be extremely short, as the M1911/A1 has a large gap (about 2mm) between the extractor hook and the breech face. (Go look!) In addition, when a round is loaded from the magazine, there is no real force except inertia that would force the cartridge out against the hook. Of course if the hook did hold the cartridge, the firing pin would still reach the primer; it jumps out a 1/2 inch or more when struck by the hammer, but that is not the way things are supposed to work.

Even if somehow the case is held back by the extractor, it will come back against the breech pretty fast after firing. I suspect that no matter what you say, your cases are really coming to rest against the chamber shoulder. If there is a roll type crimp, the crimp will be part way into the barrel leade. That raises pressures, as both the case mouth and the bullet are trying to fit into a space meant only for the bullet.

Also, cases held by the extractor or allowed to go too far into the chamber may have flattened primers. Here's why. The firing pin drives the cartridge to the limit of the extractor hook, the cartridge fires, the primer backs out into the excess headspace and expands under the pressure, then the case backs out over the primer, flattening it. Looks like excessive pressure. How do I know all this? Easy. I tried it all before some of you folks were even a gleam.

Suggestions:

1. Take the gun down and drop one of your reloads into the chamber. If the distance between the case head and the end of the barrel is less than the distance between the breech face and the extractor hook, the case is being stopped by the chamber shoulder, not by the extractor.

2. If you have an old worn out barrel, cut it in half length wise and see what your loads actually look like in the chamber.

Raymond,

Sure cartridge dimensions vary. That is why good reloaders separate brass by length and adjust the crimp accordingly.

March 23, 1999, 10:47 AM	#14
James K Member In Memoriam Join Date: March 17, 1999 Posts: 24,383	Raymond and Walt, Let's try this again. To be actually held back by the extractor, the case would have to be extremely short, as the M1911/A1 has a large gap (about 2mm) between the extractor hook and the breech face. (Go look!) In addition, when a round is loaded from the magazine, there is no real force except inertia that would force the cartridge out against the hook. Of course if the hook did hold the cartridge, the firing pin would still reach the primer; it jumps out a 1/2 inch or more when struck by the hammer, but that is not the way things are supposed to work. Even if somehow the case is held back by the extractor, it will come back against the breech pretty fast after firing. I suspect that no matter what you say, your cases are really coming to rest against the chamber shoulder. If there is a roll type crimp, the crimp will be part way into the barrel leade. That raises pressures, as both the case mouth and the bullet are trying to fit into a space meant only for the bullet. Also, cases held by the extractor or allowed to go too far into the chamber may have flattened primers. Here's why. The firing pin drives the cartridge to the limit of the extractor hook, the cartridge fires, the primer backs out into the excess headspace and expands under the pressure, then the case backs out over the primer, flattening it. Looks like excessive pressure. How do I know all this? Easy. I tried it all before some of you folks were even a gleam. Suggestions: 1. Take the gun down and drop one of your reloads into the chamber. If the distance between the case head and the end of the barrel is less than the distance between the breech face and the extractor hook, the case is being stopped by the chamber shoulder, not by the extractor. 2. If you have an old worn out barrel, cut it in half length wise and see what your loads actually look like in the chamber. Raymond, Sure cartridge dimensions vary. That is why good reloaders separate brass by length and adjust the crimp accordingly.