Once-Fired 9mm Brass exceeds SAAMI max length (Federal)????

[azrocks]

I must be doing something wrong, but what that something is I have no idea.

Most of the brass I've been using has been sourced from shooting Federal 9mm 115g target loads (purchased at WalMart). Since I shot them myself, I know they're once-fired.

I got around to carefully measuring a sample of 100 of these once-fired cases this weekend - AFTER RESIZING / DEPRIMING (but before belling) - and approximately 30% of them exceeded the SAAMI max length spec of .754 inches. The range of lengths varied from a low of .750 to a high of .759. The average for all 100 was just a hair under .754.

Every forum I've visited has countless posts along the lines of "No need to trim auto pistol brass" and "I never trim 9mm brass" or "If I had to trim pistol brass I'd stop reloading". Yet I'm finding 30% of my once-fired Federal brass to exceed max length?

Am I missing something here? If brass stretches more through repeated reloadings, and I'm already at or over the max spec after using them once, something just aint right.

 

[Rule3]

SAAMI .754 - .010

OK, I fixed it. I was using the new CORE math

 

[ReloaderFred]

Semi-auto brass has a tendency to shrink through repeated firings, unlike rifle brass, so it's not going to get longer with each loading. Check them in the barrel of your handgun, and I'm betting you'll find that it will lock up just fine. After all, the chamber they're going to be fired in is the true gauge of whether or not they're "in spec".

Hope this helps.

Fred

 

[mdi]

SAAMI data is "sorta" different than that in reloading manuals. SAAMI drawings will show a dimension with a tolerance (+/-) and manuals give a max. dimension. My SAAMI download shows 9mm Para. case length to be .754" -.010" (.744"-.754"), and my Lyman manual just says .754". The SAAMI minimum chamber length is .754" with a maximum length of .776", which would tell me you brass is safe.

I haven't measured a 9mm case that I can remember (started 9mm 17 years ago), but I use the "Plunk Test" for all my 9mm and 45 ACP loads. If it "plunks" it'll chamber and it's safe...

Also be aware that any ding or burr on the case head will affect OAL measurements (BTDT. I chased a .010" variation in OAL only to find my Garand was dinging the case rim, making them appear .010" longer...)

 

[azrocks]

Thanks for all your help, gents! That completely clears things up & answers a few questions I hadn't even gotten around to asking!

 

[243winxb]

SAAMI lists the 9 mm Luger case length at a maximum of . 754"

The chamber length or headspace, is listed as a minimum of .754" The maximum chamber is listed as .776"
If your gun has a minimum chamber, brass longer may be a problem.

I would guess, only a custom barrel may have such a short headspace as .754"

There are tools , gauges to measure headspace.

http://www.saami.org/specifications_and_information/index.cfm?page=CC

 

[Sunray]

Odd even for Federal brass that's known for being softer than other brands that they would stretch that much on one firing. Isn't going to cause a catastrophe either. It might mean you'll have issues getting a fixed OAL.
The average for all doesn't matter. Set your calipres to .754" and use it as a case length gauge.
Just a hair under .754" is still under .754". That'll do. Trim the over length cases.

 

[higgite]

This thread by Walkalong might help you decide whether or not the "too long" cases are actually too long for your particular pistol(s) or not.
https://www.thehighroad.org/index.p...x-o-a-l-with-your-bullet.506678/#post-6294790

 

[azrocks]

SAAMI .754 +/- .010

.744 to .764

Just to be clear - this is NOT correct, correct?

Most people here are saying that it's .744 - .754, and that's the way I read the SAAMI spec as well.

 

[Rule3]

Just to be clear - this is NOT correct, correct?

Most people here are saying that it's .744 - .754, and that's the way I read the SAAMI spec as well.

I read it as +/- guess it is just minus. Heck, I don't know I never measure on or any other handgun caliber (except 38 special for the SW M 52 wadcutter pistol..

If the case headspaces on the mouth then how can it be minus .010 and not plus ?? The variance in chambers may make up for that

It's about 3 hairs

 

[Walkalong]

Never say never, but so far I've never had a case stick out of my 9MM Wilson case gauge because it was too long.

 

[243winxb]

Most people here are saying that it's .744 - .754, and that's the way I read the SAAMI spec as well.

You read well.

 

[243winxb]

Walkalong, can you measure your gage, might be interesting? I dont have one.

 

[Walkalong]

Best I can measure it is .755 to .756 deep.

 

[higgite]

Best I can measure it is .755 to .756 deep.

My Wilson gauge also measures between .755-.756 deep, as does my Dillon gauge.

 

[azrocks]

UPDATE:

Federal brass sucks.

I just got through measuring 100 CBC-headstamped units of 9mm brass I picked up at the indoor range where I shoot (this is the brand the range sells, manufactured by Magtech) for purposes of comparison. Of these, less than 10% were over .754" in length, and only two were greater than .755. Compare that to approximately 30% of Federal, which were often significantly greater than .001 over max.

To compare (100-count samples of once-fired brass):

Federal: minimum length: .750, maximum length: .758, average: .7536, case length standard deviation: .0019, average case wall thickness: .0116
CBC (Magtech): minimum length: .750, maximum length: .759 (one), average: .7529, case length standard deviation: .0015, average case wall thickness: .0123

Finally, I checked another 200 once-fired Federal cases for lengths above .754. Once again - approximately 30-35% exceeded .754.

 

[higgite]

UPDATE:

Federal brass sucks.

I’m sorry to hear that. I’ve reloaded my stash of 9mm FC brass 6 times, so far. I bought it as “once fired”, so no telling how many reloads some of the cases have seen. I haven’t measured it since the 2nd or 3rd reload, but it still gauges okay. Sorry that you’re having problems with it. Send it to me and I'll dispose of it properly for you.

 

[LiveLife]

I have used both old "FC" and new ".FC." 9mm Federal brass without issues (although there's slight difference in case wall thickness) in my KKM/Lone Wolf aftermarket barrels which tend to be tighter than factory barrels. Many factory barrels are made on the looser side of SAAMI spec range. As long as your finished rounds chamber fully and barrel lock up tight with the slide, you should be fine.

I am currently using many .FC. and Blazer/Federal brass, which I believe are made in the newer Speer/Vista Outdoor plant for my test loads, and no issues in my pistols and carbines.

Take the longest resized cases, drop them in the chamber and see how the barrel lock up with the slide.

 

[Rule3]

UPDATE:

Federal brass sucks.

. Compare that to approximately 30% of Federal, which were often significantly greater than .001 over max.

.

You consider .001 significant??

They fired the first time yes?

You can change the measurement by how hard you close the jaws of the caliper

Kinda splitting hairs. How many Angels can dance on the head of a pin?

I have 3 5 gal buckets of 9mm brass of every headstamp known a lot of Federal and have never ever had an issue.

 

[azrocks]

You consider .001 significant??

They fired the first time yes?

You can change the measurement by how hard you close the jaws of the caliper

Kinda splitting hairs. How many Angels can dance on the head of a pin?

I have 3 5 gal buckets of 9mm brass of every headstamp known a lot of Federal and have never ever had an issue.

Say your local authorities upped the speed limit to 120 mph. You get caught doing 121, and say to the officer, "I was only 1 mph over". To which he responds, "Yes, but you're still going FAST!"

.001 is significant in the context of the .01 range (.744 - .754) which the brass should have fell between but didn't.

Regardless, the difference in the Magtech brass vs the Federal is that A) <10% of the Magtech brass was over spec. 30+% of the Federal was, and B) Of the 10% of Magtech brass that was over-spec, the vast majority (all but 1 or 2 rounds) was only .001 over, where the 30% of Federal brass that was over spec was - in generally - significantly more out of spec.

It should also be noted that the Federal brass was all shot by me - guaranteed to be once-used from only 2 firearms - and the CBC brass was what countless other people using countless other weapons had shot. The fact it was still significantly more consistent in dimensions than Federal is telling.

I'll admit I may be splitting hairs. I'm new to this whole thing, and probably going a bit overboard. But I'm working up an accuracy load now, and the variance in Federal brass (along with its relatively thin case wall) is not a benefit in that endeavor.

 

[LiveLife]

It should also be noted that the Federal brass was all shot by me - guaranteed to be once-used from only 2 firearms

So all the new Federal brass "worked" in your pistols ... which means they should work in your pistols again reloaded.

Right?

 

[Havok7416]

.001 is definitely not significant, especially with an auto pistol cartridge like 9mm. Actually any dimension for reloading is likely to be within .001 and it's perfectly acceptable. My suggestion is to focus on the bigger issues of learning to reload (if you haven't already).

 

[LiveLife]

+1.

I'm new to this whole thing, and probably going a bit overboard. But I'm working up an accuracy load now

If you are pursuing accuracy, I would focus on:

- Maximum working OAL length for your pistols that reliably feed from magazine
- Neck tension - measure chambered dummy rounds' OAL for bullet setback
- After identifying most accurate powder charge, incrementally reduce OAL down to 1.130" to see if accuracy improves without compressing powder charge

Ultimately, it's the consistency of chamber pressure that will produce more consistent muzzle velocities which in turn will produce smaller shot groups/accuracy.

While resized case length is a contributing factor, but not as significant as finished OAL, chambered OAL (bullet setback), powder charge variance, etc.

 

[Walkalong]

Yea, can't get excited about .001 over on case length, even with the short 9MM case.

 

[azrocks]

Ultimately, it's the consistency of chamber pressure that will produce more consistent muzzle velocities which in turn will produce smaller shot groups/accuracy.

While resized case length is a contributing factor, but not as significant as finished OAL, chambered OAL (bullet setback), powder charge variance, etc.

This doesn't make any sense to me.

If the OAL is a significant factor (due to its relevance to cartridge volume / chamber pressure), then the variance in brass should be equally significant.

If I took the lowest and highest observed lengths from the Federal brass I measured - .750 & .759 - and loaded them to identical OALs, that's nearly .01 difference in bullet seating depth. Would you be happy with .01" setback? Because to my mind there's no difference between the two.

My main gripe with the Federal isn't necessarily it being max SAAMI spec. It's that it's inconsistent in length.

Also - speaking of setback - while I have yet to test it, I'm pretty sure the relatively thin case-wall of the Federal (compared to CBC) should be more prone to such issues. Any additional inconsistency seen as a result would stack on top of the inconsistency of the brass.

I agree that there are likely other factors that have a more dramatic impact on precision than the issue I'm exploring here. But choosing one brand of brass over another isn't a difficult proposition.

Regardless - how can you really tell if the changes you're making are actually affecting accuracy if your component selection is inconsistent. If I load 100 rounds of brass that varies in length over a .01 range, while testing a .01 change in OAL... will my results be meaningful?