9MM brass shrinking.

[oldreloader]

I was checking some 9MM brass to make sure it hadn't grown. Max length is .754. That would make a trim to length of .744. The short brass ranges from .742 down to .732. There is no way I trimmed it that short. In fact I'm sure It has never been trimmed. Bought as new WW Whitebox factory ammo by me and only reloaded 3 times by me with a 5gr AA #5 charge and a MBC 125 gr 9 Cone lead bullet or 4.5 Grains of AA #5 and a MBC lead 147 gr bullet. How short is safe and why did it shrink?

 

[GLOOB]

Yeah. Nothing new here.

Why? Because it doesn't stretch. For a case to stretch, the pressure has to be high enough to glue the neck of the case to the chamber while pushing the head back and/or the mouth forward. This doesn't happen in small, straight walled, low pressure cartridges.

So it will shrink just a little bit each time it's sized, as would rifle cases, if they didn't stretch at all.

You actually trim this caliber?

How short is dangerous? Well, depending on who you talk to, you can safely shoot 40SW out of a 10mm handgun. A luger case will never get short enough to even compare. To others, the world will end if you try to shoot a case that doesn't headspace perfectly. Now shouldered cases can cause problems with improper headspacing, even in a pistol. I've seen case head separations in .357 SIG, resulting in stuck cases, even with factory ammo, due to improper headspacing. But never heard of that happening in a straight walled pistol caliber.

The sticklers will say something like this: "My reloading manual says that you can trim 0.02" when max length is reached. Therefore, the minimum length of a case is 0.734". If it's shorter than that I'd toss it."

So take your pick.

 

[ReloaderFred]

In 48 years of reloading, and roughly 750,000 rounds loaded, I've only trimmed about 10 pistol cases, and those were some Federal Nickel 357 Sig cases that I was determined to make work. In my humble (ok, maybe not so humble) opinion, trimming 9x19 cases is a total waste of time and energy. I get it by the bucket full and seldom load a case more than once or twice.

Hope this helps.

Fred

 

[rfwobbly]

9MM brass shrinking.

Stop washing it in hot water !!

 

[1SOW]

9mm: I also have measured new and spent cases like you did. Interesting information, but that's all it is.

I've never trimmed a case. I reload 100% range brass and keep reloading my free brass until the case cracks or the primer hole gets a little loose--which usually happens first with my loads after many reloads.

Your sizing die will "stretch" some added length to short cases. I've also found the LEE FCD will often stretch it just a skosh more than the sizing die, but it's not critical. The bullet seating and crimping die(s) actually do push "down" on the case a little. If you want to measure cases, do so AFTER it has been resized.

If the case is solid and the primer hole is snug, keep reloading it.

 

[TH3180]

9MM brass shrinking.

Stop washing it in hot water !!

I thought it was cold water that makes things shrink?

 

[oldreloader]

LOL at RF and TH..

 

[El Chivato]

9 x 19 headspaces on the case mouth, like the .45 ACP. With repeated reloadings, it can actually be shortened because the case is being hit in the back by the firing pin, and the "Anvil" is the case mouth up at the front. This is why you want a very slight crimp, or none at all. Too much "shrinkage" and you have a lack of headspace, and it may not fire!

David

 

[gamestalker]

Call me weird or what ever, everyone else does, but I do trim my pistol brass, in fact all brass. The circumstances your encountering has happened to me before but not throughout the life of the case. More commonly with 9mm for me, but like I said it eventually starts to grow. If I'm loading some near max loads with my usual slow burning powders, they do stretch some within the first or second loading. I'm talking about 9mm in particular. And depending on the cartridge and circumstances, I'll actually find a trim to length that is just above the minimum so it will allow me to trim all of my once fired brass to the same length, this keeps my crimps consistent, mostly revolver brass.
With my rifle brass, it all gets trimmed and nearly always reaches maximum case length within the first reloading. Once I have trimmed it to it's listed trim to length, I will maintain that length throughout the life of the brass. But in this respect, it usually only needs insignificant trimming to maintain same case lengths. I think this is because I neck my rifle brass which seems to keep the brass from growing once it has been fire formed completely, 1 or 2 reloadings usually does it.

 

[Lost Sheep]

Alternative headspacing

Thinking about El Chivato's post (#8) and Gloob's post (#2), I want to point out that many semi-autos will headspace on the extractor. That is how you can shoot (unreliably) .40 S&W in a 10mm and 380 ACP and 9mm Makarov in a 9mm Parabellum. This is NOT a good practice, as the extractor is not designed to act in this manner and is not 100% reliable in doing so.

Single action revolvers (without extractors, but using ejector rods instead) don't do this.

For an example of a revolver designed to do this, research the Medusa Revolver.

As always, verify for yourself everything you learn from casual sources. In life, believe only half of what you see and one quarter of what you hear. That goes double for anything you get from the internet.

Lost Sheep

 

[918v]

Get a Lee U sizer die. It will size the case more, thereby lengthening it.

 

[Rollis R. Karvellis]

Most shrinkage will happen in the dryer on hi heat.

 

[918v]

Thinking about El Chivato's post (#8) and Gloob's post (#2), I want to point out that many semi-autos will headspace on the extractor.

There is about .030" of slack between the case and the breechface while the case is being held inside the extractor hook. A 9mm chamber is cut to a .762" depth as measured from the breech face to the free bore. 99% of cases will headspace on the case mouth. This is true of other tilt barrel semi-autos as well. You need that much clearance for the case to feed, as the case slides inside the hook while chambering. The extractor does not snap over the case.

 

[1SOW]

918v: Thanks. Good info.

You need that much clearance for the case to feed, as the case slides inside the hook while chambering. The extractor does not snap over the case.

Some time ago: To get rid of three poorly seated and slightly damaged 9mm cases with primers, I hand chambered the primed cases and fired them in the garage. BAD CALL. The tip of the extractor claw snapped off.