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Old November 11, 2012, 12:13 PM   #29
Join Date: March 4, 2005
Location: Ohio
Posts: 13,722
Correcting some misinformation


Take a look at the SAAMI drawing for 9 mm Luger. It likely answers a lot of your issues.

Note that the diameter of the case mouth of a loaded round is 0.3800" -0.007", or 0.3730" to 0.3800". Set your crimp die so the case mouth diameter falls into that range.

Note that the COL is 1.000"-1.169", and not 1.100" minimum. I don't know where you got that.

Keep in mind that SAAMI specs are for manufacturers to follow so their ammunition is compatible with all brands of guns and magazines. If something else works better in one of your particular guns, you can use it. It just won't necessarily work in some other gun. The main thing is that you work your load up in your gun with your seating depth, while watching for pressure signs.

Also note that while commercial jacketed round nose bullets tend to have elliptical noses, many makers of molds for cast bullets seem to have found that harder to cut than just a simple hemisphere on top of a conical section (Lee molds, for example). That shape is shorter and fatter than an elliptical nose profile is for a given weight. It is also often fatter at the ogive forward of the bullet bearing surface (the cylindrical portion). This forces you to seat deeper for the same feed reliability.

You may already be at your best seating depth. The "plunk" test works when a cartridge headspaces on the case mouth, as is the design for this cartridge. However, with lead bullets it often improves accuracy and reduces leading if you headspace on the bullet instead. This means the bullet sticks out just enough to come to a rest in the throat of the barrel just before the case mouth makes it all the way to the end of the chamber. This is because it is easier to distort a lead bullet on its way into the throat, so it's important that it start out straight. Jacketed bullets are tough enough to tend to align themselves on the way into the throat without distorting. Below is how this looks in the .45 1911 (third from left) but it applies to the 9 by analogy. It won't make so pronounced a "plunk", but it shoots well.

I don't know where the guys calling for .358" bullets are getting that idea. It is standard practice to make commercial lead bullets 0.001" wider than bore groove diameter. While the .38 Special, .357 Magnum, and .357 Maximum cartridges all have .357 groove diameter barrels and therefore get .358" cast bullets as standard, the .380 ACP, 9 mm Luger, .38 Auto, and misleadingly named .357 SIG all have .355" groove diameters and therefore will want .356" lead bullets standard. Unless slugging your barrel has shown you to have an oversize groove diameter, .356" is what you want.
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