case length inconstant?

[karlrudin]

I did a search of the forums before I posted this. I seen lots of post on varying OAL but nothing on varying lengths of cases of 9mm. I know cases vary and that is normal(manufacturer, amount of reloads, pressure, etc)but what I am finding hard to understand is this. I recently started reloading 9mm Luger and found during the reload process is that the case lengths vary from BELOW minimum to just short of trim length. All these cases new factory, fired in the same gun, and all were from different manufacturers. Since 9mm headspaces off the mouth of the cases, shouldn't their length be between trim length and maximum length. I've been loading rifle cases all my life and I pay close attention to cases length and trim amounts so I can get the most use out of a case but to also know when to discard because of thinning and trimmings. So, any input would be appreciated.

[rintinglen]

Welcome to the real world. Short cases are far more common than long ones in handguns--I bought some starline 38 Special nickel cases to use for +p loads. I measured one hundred of them. NOT ONE WAS WITHIN 5 THOUSANDTHS OF SAAMI MAX, and several were under SAAMI mini. Case lengths ran from a low of 1.132 up to 1.149 with the media average being about 1.143. Do you think I could get a consistent crimp? The 9 mm is even worse, especially if head stamps vary. Case lengths have run from .738 to .754 in my experience from the same box of factory ammo. (Winchester White Label).
However, all is not lost. Case length matters more in rifles than in handguns.
In most cases, it doesn't affect much of anything if your 9mm ammo varies a mite in case length. There are darned few handguns so chambered that can tell the difference and even fewer shooters sufficiently skilled to extract the level of accuracy that uniform case lengths can provide. Take thirty cases of the same head stamp, trim 15 and leave 15 alone. Load them with identical charges and boolits. Fire six five shot groups alternating between the trimmed and the untrimmed cases. I'm betting that any difference in group sizes will be statistically insignificant.

[tazman]

Partly because of their shorter length and partly due to less chamber pressure, straight walled pistol cases don't stretch as much as rifle cases do. You get more damage from belling and crimping the case mouth than the resizing process. Usually the cases will crack at the case mouth long before you would get separation due to thinning of the brass near the case head.

I have also found the case length to vary a lot in 9mm brass. I have never had it effect the function or accuracy of the load. I have never had a cartridge in my 9mm fail to chamber due to case length variations. I know I am not a good enough shot to tell the difference those tiny variations would make anyway.

[karlrudin]

So the bottom line is not to worry to much about length unless it is noticeably shorter and not to worry about stretch because the necks will crack long before then. Got it. Like I said, new at pistols and wanting to get a base line to work from.

[Alferd Packer]

If you're new to loading 9mm, try to pick thru and sort them by headstamp.
When you get enough of the same , load them and try shooting some, but only load a box of 50 .
If they work ok, then try more, remembering the best load is the one that just makes the pistol function and shoot reliably.
Also remember, the hotter the load, the shorter the caselife. Maybe one-three loads hot to five-seven with minimum loads.
Again, that all depends on how loose the pistol chamber is compared to how tight your sizing die is= case life too.
I don't expect these'll be combat loads in any case.
The necessary belling and crimping take their toll as well.
Nickle cases seem to split quicker for me. I size all my nickle cases with lube in a steel die when I have time and they last longer for me.
The carbide dies are quicker, easier and burnish the cases, but they also eat them quicker too.
As time goes on, everything that is plentiful now seems to become scarce.

[Ed_Shot]

My gripe about short 9MM cases is that my M-die does not adequately expand a .740 length case if I have it set to adequately expand a .746 length case. I think you have to draw the line somewhere or you are shaving lead with inadequately expanded short cases. All my 9MM cases are range pick-up. I measure all and sort by headstamp trashing those shorter than .746 (@ 3% ~ 5%). I have given up on trimming long 9MM cases.

[karlrudin]

If you're new to loading 9mm, try to pick thru and sort them by headstamp.
When you get enough of the same , load them and try shooting some, but only load a box of 50 .
If they work ok, then try more, remembering the best load is the one that just makes the pistol function and shoot reliably.
Also remember, the hotter the load, the shorter the caselife. Maybe one-three loads hot to five-seven with minimum loads.
Again, that all depends on how loose the pistol chamber is compared to how tight your sizing die is= case life too.
I don't expect these'll be combat loads in any case.
The necessary belling and crimping take their toll as well.
Nickle cases seem to split quicker for me. I size all my nickle cases with lube in a steel die when I have time and they last longer for me.
The carbide dies are quicker, easier and burnish the cases, but they also eat them quicker too.
As time goes on, everything that is plentiful now seems to become scarce.

I tend to load my ammo near the bottom with anything I load then work my way up and stop if the group starts to open again. In some instances this is well below max. In others I tend to stay a full grain(in rifles) below max. If it hasn't started grouping by then, time to move to another load. I did find in my cz-52, it wouldn't function the action with the bottom loads and had to move up one. Once it functions and I can keep 8 rounds in a 8.5 x 11 piece of paper @ 25', I'm done. Rifle is the only things I strive to get tiny groups :).