9mm cartridge dimension variances???

Philadelphia Patriot · Jul 29, 2018

I bought reloaded 9mm online over a year ago. The ammo is reloaded from different manufacturers’ cases. I have a few Winchester rounds where the dimensions of the brass right above the rim (where the extractor claw fits when chambered) of the cartridge are different. At that location the cartridge is wider. Also the sloping portion above that area is a little longer/taller than other cartridges too. I have brass with the same Winchester markings that look normal compared to these different Winchester rounds. Below are 2 pics. The pictures aren’t great but trust me when I say the dimensions don’t match 100%. Is it normal for different manufacturers to have slight differences in cartridge dimensions or is there only one strict diagram to follow?

Nevada Ed · Jul 29, 2018

Not all resizing dies are the same spec's. and how far down the
die goes on the case and the belling of the case, can all make a
loading different from maker to maker.

All one can ask for is that the ammo will feed in your weapon,
depending on your pistol's camber and feeding system.

Some pistols are "Tight" while others loose in their allowances,
on how they accept ammo.

HKSmith · Jul 29, 2018

There is "one strict diagram" to follow and you can find it at the SAAMI website. All the major gun and ammo manufacturers agree to follow these specifications so that consumers can be confident that ammo marked 9 mm (for example) will safely fit and function in a gun chambered for this cartridge. These specifications all have tolerances, so ammo from different lots or manufacturers won't necessarily be exactly the same. For example, the rim diameter for 9 mm can be between 0.384 and 0.394 inches and the angle of the taper above the rim can be between 25 and 35 degrees.

I'd be interested to know if your cartridges fall outside the SAAMI specs. Just as an aside, current prices for factory 9 mm are so low that I don't see the point in buying reloads (which sometimes seem to be more expensive). Reloading your own of course is cheaper.

Pisgah · Jul 29, 2018

Published cartridge dimensions are "nominal" -- which means, they are the design specs, but there are acceptable +/- tolerances for most if not all dimensions. I would be surprised, if not shocked, to find two cases from two manufacturers that were identical in all dimensions.

Nevada Ed · Jul 30, 2018

As a note;

When I see ammo that has the brass expand around the bullet...

I wonder if the bullet dia. is .355" or if Military brass was used.

Bulging and off set bullets make for an ugly loading and show poor quality.

alwslate · Jul 30, 2018

Case differences between brands of semi auto pistol ammunition is
the norm. Look at new factory ammunition of any pistol caliber and you
will see differences between the rim shape and groove depth and width
between various brands. Just part of why some brands may function
more reliably in your gun.

WR Moore · Jul 30, 2018

OK, you seem to be concerned about the configuration of the extractor groove.

First, let's look at some back ground. Here in the US, SAAMI established the critical dimensions of cartridges submitted to them. I believe it's CIP that does the same things in Europe and one would expect there's some consultation back and forth.

The critical dimensions are established so that all cartridges of a given caliber should fit in a standard chamber and fire safely. Some other dimensions are left up to the ammunition makers.

Now, specifically concerning the 9 mm, there appears to be some variation in case rim diameter world wide. This is probably due to the widespread use of the 9 mm in sub machine guns. I generally suggest that if you're going to load 9 mm and may end up with some foreign brass that you use a .38 Super shell holder to allow for occasional oversize (from SAAMI spec) case rims. Lyman uses the same shell holder for 9 mm/.38 Super. Other brands don't, and the different shell holders frequently have a different height, which affects case mouth flare and bullet seating.

Your concern appears to be with the clearance cut dimensions forward of the actual extractor groove. This is one of those areas where the designers get some freedom so long as the critical dimensions that affect commonality, function and safety are within specs.

In short, don't worry about it.

9mm cartridge dimension variances???

Philadelphia Patriot

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Nevada Ed

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HKSmith

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Pisgah

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Nevada Ed

US Veteran

alwslate

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WR Moore

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