Scorched (?) Guardian .32 brass

[bearcatter]

I mentioned this as part of another post, but no one commented.

After my first range trip, I collected what empties I could. I was shooting Aguila and Remington, both 71 gr FMJ. On all of them, the forward half of the case looked scorched, for want of a better word. Under the soot, the brass was darker, dull, and splotchy compared to the rest of the case. I didn't see much of this on other empties scattered around the range. I haven't had a centerfire semi-auto in years, just revolvers, so this is kind of new to me.

Some friends that reload say it could be blowby from a loose chamber or low charge, sign that the brass is not sealing the chamber on firing. I think it's only because .32ACP headspaces on the rim, not the case mouth. That could leave a thousandth or so clearance at the case mouth, allowing this "blowby" ? Plus, there would be some gas exiting the rear of the barrel as the round extracts.

I'm happy with the gun, but is this an issue or not?

[Warthog]

Pix?  Would help to see some of the brass to diagnose what is happening

[bearcatter]

Don't have a camera that would focus close enough to show anything. Just picture light tarnish with a few small spots here and there, and the rest of the case shiny new.

Looking around online, it seems to be normal. Polishes off easily, so could be from oily film left in manufacture, or slightly short cases which are said to be common. Anyone else see it on their .32 brass?

[bearcatter]

I almost forgot that NAA does like Ruger and includes testfire brass with a gun. (They shoot a full mag through each gun.) I got it out, and it matched what I fired, except it was Winchester brass. I gave up and emailed NAA with that point and my description.

Basic reply was that it is fine, perfectly acceptable. Not exactly a detailed reply, but settles the question.

[adp3]

It's been a while since I had a Guardian so I don't recall how closely the design follows a Seecamp.  On the Seecamp .32's the chamber is slightly enlarged about mid-point.  This allows the brass to swell a bit and slightly retard the slide's rearward movement.  This swelling allows carbon blow by and you end up with sooty cases.  If you use a micrometer on your cases you can see if this is also the case with .32 Guardians.  I've had Seecamps and Guardians.  I much prefer the Guardian.  For me, the Seecamps only advantage is that it's slightly lighter.

Brst Regards,
ADP3

[Warthog]

Well, mine has been a pretty good gun.  I haven't had any issues reloading the brass either.

[bearcatter]

From looking around online, it would seem cartridges that headspace on the rim (.25 ACP, .32 ACP, .38 Super)  have their own peculiarities. The cases are made a thousandth or so short, to ensure the rim seats. The guns are chambered a bit deep, for the same reason. This leaves the first fraction of case in mid air, and helps channel the gases to where it does contact the chamber. Hence the blowby.

Also, the .32 ACP is actually a pretty hot cartridge on its own, moving a 71 grain bullet with the energy and velocity of a .38 Special. Pressure peaks quickly and shortens extraction time, increasing the chance of blowby. The cartridge has barely finished burning when it starts extracting.

FWIW, the Lee-Enfield and Mosin Nagant rifles use a semi rimmed cartridge, and the .500 S&W Magnum is semi rimmed.