Am I being too anal sorting my 9mm bass by length?

I definitely can't shoot that well any more, but I have always trimmed my handgun brass. Actually, this is where my OCD comes into play I think. So if trimming your handgun brass helps you sleep better at night, as it does for me, then have at it. After all, they do include a trim too length for handgun brass in all my books, so why not, right?

On a more serious note, I can never fault anyone who desires to follow the data as it is written. And when it regards a high pressure handgun cartridge where a variable of only .010" can have a noticeable effect, such as 9mm, it can only help to produce more consistent pressures. And even more so if everything else is being performed with such precision.

I like threads like this cause it sends a message, that it's ok to follow the book to a "T".

GS

I'm getting a headache just thinking about sorting 9mm by case length.

Lets say I set my dies up with a piece of brass measuring .9 inches long and the bullet is being seated .25 inches into the case for an OAL of 1.5 inches. If i keep using the same shape/style bullet through the entire batch that I used to setup the dies, but I slip a case into the batch that is 1.1 inches long, how could there NOT be a deeper seating depth?

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I refer to seating depth from the bottom of the case to the base of the bullet. Your looking at it from the top of case to base of the bullet. The area between the base of the bullet and the bottom of the case (head) is what's critical to the pressure of the cartridge when it's fired.

Yes, the seating depth from your point of view will change because of the cases not being trimmed to the same length but the combustion area inside the case should always be the same if your dies are setup correctly.

I usually go through my 9mms "working brass" once a year to pick out the ones shorter then .740" because it affects my taper crimp and a few other things. Even if it is So short that it doesn't headspace the extractor will hold it in place so it still fires and no one really notices because it just doesn't cause any detectable malfunctions.

If you don't sort them for length, they will still fire just the same.

when I 1st started I trimmed the cases after sorting them because the "books" said to do it.....then reading and comparing different educated members on here that I respect their wisdom....rcmodel +walkalong for two examples ...also what I learned when hands on doing I relised it wasn't going to make a different result I do separate by head stamps ..that's where it ends...I relised my time was worth more doing something else sorry about the spelling

Technically variations in case length does have an affect on performance. Practically, it does not matter unless you are loading Max Loads for all rounds.
What it affects is the distance from Ogive to Lands, and Bullet surface contact with brass. Look at the attached PPT for explanation.

Because the 9mm headspaces on case mouth.


Remember technically vs. practically: what:

Compare the results and let us know what you find out

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This please. I'd like to see some stats on this. Everyone is saying it doesn't matter but I'd like to know for sure.

tightgroup tiger said:

I refer to seating depth from the bottom of the case to the base of the bullet. Your looking at it from the top of case to base of the bullet. The area between the base of the bullet and the bottom of the case (head) is what's critical to the pressure of the cartridge when it's fired.

Yes, the seating depth from your point of view will change because of the cases not being trimmed to the same length but the combustion area inside the case should always be the same if your dies are setup correctly.

I usually go through my 9mms "working brass" once a year to pick out the ones shorter then .740" because it affects my taper crimp and a few other things. Even if it is So short that it doesn't headspace the extractor will hold it in place so it still fires and no one really notices because it just doesn't cause any detectable malfunctions.

If you don't trim them, they will fire just the same.

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YES! I see! The area between case base and bottom of bullet will not change. So the difference has be to be found at the top where the case mouth terminates in relation to the bullet.

So OAL won't change either but there will be a difference where the case mouth meets the crimp die. This could impart 'more' crimp if its longer or less crimp if its shorter. Depending on the type of crimp desired and the particular die this could be a LOT or a LITTLE. I'm tracking..... So yes, it would all come down to headspace and crimp.

For whatever reason, your explanation clicked. Thank you!!

Don't forget, there is a hyphen in anal-retentive.

: exhibiting or typifying personality traits (as frugality and obstinacy) held to be psychological consequences of toilet training
— anal–retentive noun
— anal–re·ten·tive·ness noun

I never bothered measuring or trimming 9mmx19 fired brass. 50K+ rds to date reloaded. It mostly headspaces against the breechface with the extractor holding it back.

The 9mmx19 cases tend to get shorter, not longer with repeat firings so they won't get too long to fit into the chamber. The ones with several firings have the headstamp mashed flatter. In fact they can get oversize rims (if you're gaging them) with several repeat firings.

Yup - anal. Just load 'em and shoot.

I don't know if it matters, but I don't sort them according to length, I just chuck em up in the trimmer and take them all down to .740". I see little point in spending more time measuring, considering the trimmer gets them all consistently the same.

As for why I do it, again it's published, 9mm head spaces off the mouth, and I load full tilt. Beyond that, I have not personally heard of anyone ever having any serious problems when not going the extra mile, or two.

And my shrink says keep on trimming them.

GS

mixed case lengths

Potatohead said:

This please. I'd like to see some stats on this. Everyone is saying it doesn't matter but I'd like to know for sure.

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Potato, the 9mm shooting I do is in a casual IPSC context, not bullseye or benchrest pistol. Practical accuracy and reliability (I.e. chambers, fires and ejects) is what I seek and get.

The only thing statistically valid is that this has worked for me through near 15,000 rounds. At the beginning I measured a couple hundred mixed resized cases and found them to fall within an 7 to 9 thou range, mostly slightly short of book trim-to length.

I just now quickly measured a 100ct random mixed resized & primed sample and found the lengths to vary from:
.744 (one case),
.745 (10 cases),
.746 (19 cases) and so on to
.750 (8 cases),
.751 (4 cases),
.752 (1 case).
The trim-to length in my Lyman's is .751". Lyman's SAAMI drawing tells me new case length averages .754" (I've never owned a new 9mm case).

At the beginning my reloaded match ammo was put through a case gauge or chamber checked. I stopped after a year as what I do works and to tell the truth the stakes are not all that high.

My anecdotal numbers support what others have noticed, which is that 9mm cases don't grow, they become shorter. So then there's no point in trimming.

edit: as mentioned by rodregier, case inspection remains an important safety and performance step. The rims get mashed, cut, deformed, dished. The primer holes loosen. The mouth cracks, splits.
If a guy wants to feed his inner OCD, case inspection is a useful way to feed the beast.
Trimming, not so much.

"Am I being too anal sorting my 9mm bass by length? "

If I get caught with a 9mm BASS the FWC will arrest me and I will lose my boat all my gear and get a big fine.

So yes I sort them by size and let those go.

Yes. Life's too short to play with your food.

I only sort them by headstamp since I've noticed differences in OAL length with different brands of brass. I also sort the "once fired" from the "more them once fired" and that's it.

Yes you are.

If you are concerned with length, just trim them all, sorting takes a lot of time and doesn't solve the length issue.

I don't bother with case length. I sort by manufacture date zodiac sign, weather pattern when first fired, and the phase of the moon on reloading.


I can't say I've noticed much difference in my marksmanship though.

You should start loading for rifle if you like sorting and case prepping brass! First you can re-size, trim, chamfer, primer pocket clean, crimp swage, flash hole deburr, and clean all of them. Then you can sort by both head stamp and case weight! If you're really into it, put those weights into excel, do some statistics, make a histogram for fun, and only load the cases within 1-2 sigma of the mean.

Yes, I'm that anal-retentive, but I still don't sort any pistol brass that goes in a magazine, other than 45s for small primers... whoever thought small primers were good idea.

9mm bass is pretty small. Put that guppy back and go catch a real fish...

Sorry but I couldn't help but be a spelling nazi this time.

You must have a lot of time on your hands.

9mm & straight walled like- case length only affects headspace. IMHO, forget case length and concentrate more on same headstamp, consistent primer flash holes, etc. Good Reloading, Catpop