Case trimming... what am i not getting?

So I inherited a Lyman power case trimmer from my uncle who passed away a few months back. I know very little about case trimming, and haven't really seen the necessity to mess around with it. My multiple times fired/reloaded brass has always functioned fine in my ARs. However, I figured I have one now, and I want to start loading more than just plinking ammo.

I started with .223, as it's the round i'm most familiar with. My Speer reloading handbook says to trim to 1.750", which I did. After doing so, I noticed the neck is now only .1", which I thought was ridiculously short (it even looks weird). So, I started measuring my manufactured ammo (winchester .223), and noticed that it's case doesn't meet the specification of my Speer handbook. The manufactured ammo exceed the "Max Case Length" by almost .1" of an inch.

I noticed very similiar results when measuring out manufactured .270 Remington ammo. The case exceed the Speer "Max Case length" by more than .1". It also exceeds the Max Cartridge Length, though, not by more than a few hundredths.

Overall, I trimmed more than a tenth of an inch off of my .223 brass. It has a ridiculously short neck now, but it measures out to 1.750".

Am I doin' it right?

-ska-

No, you are not doing it right.

At most, you'll cut 0.015" off the case mouth.

What type of dial caliper do you have?

After trimming .223, you neck length is 0.1"?? That is definitely not right.

You are sizing, then trimming- correct? As RedFalcon said, you should only have to trim a bit off after you size.

Someone with more experience will come along soon to give you better info.

Are you using a digital calipers? When you close the jaws does it read 0 or .100?

Max Case Length 1.760", Trim To Length 1.750".

Cases "grow" when they expand when fired, then are resized to fit in the chamber.

Alright... I have to report back that apparently I don't know how to read/operate dial calipers. I "checked" my calipers on a ruler at whole values (1", 2", etc), but didn't check them at .25", .75" and so on. When I did (mostly because of the gentleman suggesting that my calipers maybe reading .100 at closed) It turns out I was reading .65 as .75. So I actually trimmed my case down to 1.65".

Even though I revealed that I'm apparently an idiot , I do appreciate the help, as I would have most likely just shrugged, and trimmed a couple hundred rounds down to 1.65", had I not asked. I knew something wasn't right, and sometimes it helps just bouncing an idea of people. Thanks guys.

-ska-

how many did you trim? you need to scrap the brass or give it to somone who's converting .223 cases to 300 blackout

OK, get some digital calipers. E-Bay, Harbor Freight, Home Depot, etc. Much easier to read and avoid the mental gymnastics with the indicator.

Not a problem, we are here to help each other.

<offtopic>dryflash, you have some of the most distrubing reloading photos I've seen</offtopic>

OP, bear in mind that whether you use digital calipers, or analog (I far prefer analog, but it's a personal taste thing), you must check the zero - you can make the same mistake with a pair of digitals that you made with the analogs. Just FYI.

Pic from an old thread, some 380 range brass.

Now that the O.P. is well taken care of and Dryflash3 provided some entertainment. I don't see the harm in adding one more entertaining picture on the same vein.

Picking up some range brass last year I found this one. I keep it for the wild eye reactions I get.Left to right, new .40 S&W cartridge, somebody's fire-formed .40 to .45 case, and normal .45ACP.
What do you bet it wasn't magazine fed? There was only one.

That looks like it was a wild ride! I wonder what the piece looks like after that?

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