9mm case lengths highly variable?

[viejorifle]

Just learning to reload. Starting with 9mm Luger casings fired in my P226, and for reuse in same weapon.

Lyman 49th ed. says to trim to 0.754, Lee's 2nd edition Modern Reloading also gives same figure.

When I put a dial caliper to my brass, they range from 0.753 to 0.742 in case length. The average length over about 200 casings is in the 0.745 area.

If I understand correctly, my Lee case trimmer will not remove anything from these casings.

If I were to assemble cartridges with these casings I believe there would be excess headspace which I've read should be avoided. Am I wrong? Why did the fire OK previously?

Newcomer kind of confused here.

Information

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[WarPig1976]

No, your good, I have NEVER trimmed a pistol case, revolver/rifle yes. As a matter of fact it's not unusual to open a bag of new rifle brass and most cases be under Spec by a few thousands.!!
Pistol brass gets picked up, tumbled,reloaded without ever seeing a set of calipers. I don't know anyone who does either.

I should add headspace isn't an issue with straight walled cases as found in pistols

[viejorifle]

warpig1976:

Thanks for your response. Being a new reloader, this is my very first batch, and the books all warn to heed the directions lest a gun explode in your hands. So I'm keyed to being ultra cautious.

If the reality is that cartridges will be somewhat different, and still safe to shoot I can proceed with my climb up the reloader learning curve. Still this batch will only be 10 rounds in size. I'm feeling my way slowly.

Kind regards. Ray

[WarPig1976]

After a while you'll be a pro and know what to careful about and what the corporate lawyers had put into the manuals. Wait until you start reloading rifle rounds and your COAL's vary by 10 thousands!!! that's a real mind bender until you realize why and there's nothing you can do, well you can but in milsurps its mute. Take your time and enjoy yourself, the fellas here are very knowledgeable and are always willing to help.

[CrossedCannons]

Are you measuring 1X fired brass or 1X fired & resized brass? Resizing will lengthen them and this is the length you want to pay attention to

A long time ago, I bought a bunch of 30 carbine brass and found they were all "too short", only to realize I was measuring them at the wrong point in the reloading cycle - duh

If 30 carbine is considered a "straight walled pistol case" (I've seen it stated as such on the internet), then the above advice to ignore case length is wrong (i.e. dangerous). Just starting out, measure every thing, be AN.., then learn from your own experience where you can take shortcuts. Never rely on the experience of others to short circuit The Process.

[browningautorifle]

Warpig was specific about rifle cases and a .30 carbine is a rifle. And before one starts the argument about .30 carbine "MAYBE" being a pistol case. I've shot Remington fireball and Thompson Contender in .308 and 45-70. They're rifle too. Reloading manuals put things all over in their books.

His advise on not bothering with too much case prep for pistol is sound. Use them until they crack and salvage them out. You'll probably lose them before that even happens...

[villiers]

9mm Para (Luger) seals at the rim of the case and thus needs to be the correct length. If the case is too short, gas escapes which you´ll be able to see by the burn marks on the outside of the case neck. Fired cases are usually too short, but revert to the correct length (19.0mm) after sizing. So if you measure cases BEFORE sizing, they´ll normally be too short. Luger, who designed the 9 Para, realised that that there was a problem in that the cases had to have a concentric rim and be the correct length to seal adequately. He propounded a stepped chamber which some weapons manufacturers still use. The "step" leaves a distinct mark, similar to a "bottle neck" on spent cases.

[jmoore]

Regarding cartridge cases, the main thing to avoid is "too long"! Can lead to rather more serious problems than too short. For those types that take a crimp (not 9x19) a uniform length is useful. Otherwise, it doesn't make a big difference. (Think .38 Spl in a .357 Mag chamber.)

[WarPig1976]

CC, the fact of the matter is nothing I stated is unusual or unsafe. Of course over time Viejorifle will gather information from different sources and come to the same conclusion, he just heard it here first.
As far as .30 carbine being a straight walled pistol case.....Don't believe everything you read on the Internet...

[Bruce McAskill]

I've been reloading 9mm for almost 40 years. During that time I have never ever had to trim a 9mm case what so ever and some of them have been fired over 20 times. Any normal pistol round do not need to be trimmed. The operating pressures involved are too small. The 30 carbine is and always has been a rifle case and has a much higher operating pressure then most pistol rounds. They do stretch and quite a bit so they do have to be checked each time they are loaded.