Why Are My .45 ACP Cases Too Short?

[Louca]

Last night I was preparing for some shooting with a friend today. Long story shortened, I found out my .45 ACP brass length is, on average, .0085" shorter than the published standard length of a case (0.898"). And it has me wondering why.

The cases I measured have been shot and reloaded many, many, times. And I am willing to believe it is time for some new brass. But how in the world are the cases getting shorter? I full-length re-size the brass every time. I have NOT ever trimmed the cases, nor do I ever de-burr the mouth of the case. I thought, if anything, the case might lengthen over time, but not shorten. Any ideas?

For reference, all cases were fired in a Colt Series 70 Mk IV 1911. Thanks.

Lou

(Apologies to any who read multiple forums since this is also posted to THR).

[g.willikers]

Are you measuring before or after resizing?
They get shorter when fired and lengthened when resized.
When the rounds are fired, the cases expand to seal the chamber.
That makes them a little shorter.
Measure them again, after they have been run through the resizing die.
There are exceptions, especially for bottle necked rounds and for very tight chambers.
But generally speaking yours seem to be acting normally.
Besides, is that small amount really going to make a difference in a .45acp?

[Brian Pfleuger]

Handgun cases often get shorter with use. It's common and of no concern. It's also why they never have to be trimmed. Load 'em and shoot 'em.

[Real Gun]

It will effect how the rounds head space and where the bullet winds up relative to the forcing cone. If the rounds are chambering okay, you should be within the range in which the gun will function.

[polyphemus]

Ordnance case length .898" +.0"/-.006"
As stated above they'll gain a couple of thou. after re size and you'll be
good to go.The concern when cases are too short is head space.

[Louca]

Thanks guys. Yes, these are cases that have been fully re-sized and de-primed.

OK, here is the longer story that I shortened! :-)

There have been absolutely NO problems with these cases in my 1911 EVER. No FTEs and especially no FTF problems of not going into battery. So everything is good there. But now I am introducing two new things: some new jacketed bullets I have never loaded (shoot LSWC normally), and I now also have an HK 45C. So, just to say I did it, I took the barrel out of the HK and tested some of these new rounds in the chamber to see if it gave me that "plunk". Almost ALL the rounds did not plunk and the bullets were hitting the "rifling" (HKs do not have a rifled barrel). Even though the bullets were hitting the rifling, the case base did not ever extend beyond the barrel tang. I did not test it in the 1911, but I suspect I would have found the same thing.

I loaded for the OAL mentioned in the reloading manual for the bullets. But the manual assumes the brass is 0.898 long. With shorter brass, the bullet sticks out farther since OAL does not consider case length at all. I suppose manuals for the .45 ACP should state the length from case mouth to bullet tip, but that could not be easily measured.

Having said all that, I am really not worried these rounds will not go into battery on either pistol. I think they will do OK. But it got me to wondering why the cases were shorter.

Lou

[Wallyl]

Louca,

I do believe that the cases get "hammered" shorter upon firing. A semi auto pistol smashes the leading edge of the case mouth into the chamber. In a 9mm Luger cases, there is a taper that reduces this force. I found if I use a carbide sizer die they are shorter than if I use a steel sizer die... I theorize that the case is pulled out longer when it is removed from the steel sizer die vs a carbide. I have carefully measured this and found it to be true....FWIW...

[243winxb]

A length of 0.898" may produce better accuracy in some match grade 1911's better than the minimum length .888" This has nothing to do with COL. I measure my COL this way for a lswc. Just into the rifling for accuracy, slow fire only, not rapid fire. End play is removed. [IMG][/IMG] Click photo for larger.

[Louca]

I found if I use a carbide sizer die they are shorter than if I use a steel sizer die ... I have carefully measured this and found it to be true

Hmm, guess what kind of dies I am using - carbide! Interesting.

Lou

[Louca]

A length of 0.898" may produce better accuracy in some match grade 1911's better than the minimum length .888"

It sounds like both the case length and the bullet seating depth are important. It is easy to control seating depth, not so easy to "control" cases that are a little short.

[243winxb]

There is a slight taper to the 45acp case. http://www.saami.org/PubResources/CC...ic%20Match.pdf Sizing methods that may be tried are, 1. Size only the part of the case that hold the bullet. Sort of like neck sizing a 223rem. This was in RCBS news letter, it did not work for me. Caused chambering problems. 2. Old RCBS carbide die instructons say to keep the thickness of Nickle between the shell holder & carbide die, when setting up the die. This does work for me. The brass at the web area is not fully sized. May help accuracy if rounds feed/chamber OK.

[Brian Pfleuger]

Headspacing in a semi-auto handgun is mostly in the mind of the gun holder.

Think of it. SAAMI minimum chamber dimension is 0.898 for .45acp, maximum is 0.920. That's a difference of 0.022, which is several times what a normal headspace would be and more than double the difference between "trim to" and maximum length.

In other words, unless you've measured from the back of the barrel hood to the lip in your chamber, there's no way of knowing what your cases "should" be.

Now, with your gun field stripped, put a case in the extractor and lift it up and down. How much "wiggle room" do you have? Not much, eh? That wiggle room is the ENTIRETY of the amount that your cases can be off from the true headspace of your chamber and still headspace "correctly" on the case mouth.

Short story: Almost all semi-auto handgun rounds "headspace" on the extractor, not on the mouth or any where else.

[243winxb]

http://www.leverguns.com/articles/ta..._reloading.htm Case lenght vs Accuracy.

[gwpercle]

Stop measuring them.
Shoot and reload. Not a problem so it does not require a solution.

[zeke]

look carefully at 243winxb's picture. Notice how the case is wider near the extractor groove? 45 acp is well known for getting shorter with repeated firings and resizing, especially with carbide dies that do not resize all the way down. Eventually, in a tight chamber, you may get feeding problems going into the chamber.

Is easy to check for yourself if you have a die that will size more of or the entire case, like lee's push through set up using their factory crimp die.