headspace and C.O.L. in 45acp


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9teenEleven
August 8, 2009, 01:15 AM
I have some basic questions regarding pistol chambers as they relate to reloading. I am starting to reload for .45acp, but want to understand the function, rather than just following the numbers.

My first question involves the chamber depth, headspace, and the extractor. First, is dynamic headspace (as opposed to the static headspace of the chamber depth) determined by C.O.L. or case length?

If the answer is that the headspace is determined by case length, first, how does the extractor come into play? Second, why does C.O.L. matter for anything other than cartridge pressure and feeding?

Something that I ran across in my reading that is throwing me off is this picture:
http://img5.imageshack.us/img5/9690/45seatingpossibilitiesxyl8.jpg

The four different images imply that you can adjust headspace with your load. Should the bullet ever be touching the lands in order to obtain the ideal headspace?

This line of questions started when reading my loading manual and seeing that only max C.O.L. is listed not minimum (I am just getting started reloading). Assuming that max C.O.L. is the line you don't want to cross, how do you determine how much under max C.O.L.? Should I just forget about headspace as long as I am under max C.O.L., and worry about distance to lands, and pressure?

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Jim Watson
August 8, 2009, 06:02 AM
It is very usual to load a .45 ACP semiwadcutter bullet so the headspace is controlled by the shoulder of the bullet against the origin of the rifling, as shown in drawing no 3.

With other styles you are pretty much stuck with what you get when the round is at an OAL that feeds reliably. The SAAMI maximum of 1.275" is nearly always too long.

NoAlibi
August 8, 2009, 08:41 AM
The .45ACP case headspaces on the case mouth. It is that point on the case that stops the cartridge from going further into the chamber.

In the diagram on the right, the gun should not go into battery and should not be able to be fired.

In the diagram on the left the case is so short that the extractor holds the case and the case mouth does not reach the the chamber ledge that it would normally contact. I have experimented with trimming cases so short that the cartridge headspaced on the extractor and the two 1911s I tried them in DID fire. Even though the .45ACP is a relatively low pressure round, it still might not be a good idea for repeated firings in this condition in the event it may cause case head separation as it does in high pressure cartridges. Perhaps someone with more experience could chime in here.

BTW, using the barrel hood as a measure of proper headspacing may also not be a good idea, since that part of the barrel may vary in different models of guns. Head space gauges are cheap and it's the best way to go. A caliper can be used, but it's more tedious if many cases are involved.

Walkalong
August 8, 2009, 09:06 AM
Headspace is practically a non issue in .45 ACP. Things have to be really wrong for it to be a problem. If your pistol is OK mechanically, you are fine.

Seat the bullet so it feeds great, or if you think you can get better accuracy seating the bullet to touch the lands, and it will feed, fire, and function at that O.A.L., go for it.

The Bushmaster
August 8, 2009, 09:08 AM
The .45 ACP is one of the easiest rounds to load for. One reason for this is it's forgivness of our paranoid attitude toward absolute correctness or our habit to be down right sloppy and careless. The diagram above is an excellent visual aid when reloading almost every semi-auto due to the fact that in most semi-autos the hood will be in contact with the breach face with only a few thousands of an inch space. If you have loaded them like figure two you stand a chance of a missfire because the firing pin won't be able to hit the primer hard enough. In most cases though, the extractor in .45 ACP will hold the case well enough, but should not be counted on. In the last (fourth) figure. You will have a problem with the slide going to battery or having lead bullets slammed into the leades.

I've been loading .45 ACP for over 22 years without one single missfire in any of my 1911s and I really haven't paid that much attention to case length except for my Colt.

Headspace gauges for .45 ACP? Maybe if you are shooting compitition. Other then that.........Ppphhhtt!!!

NoAlibi
August 8, 2009, 10:03 AM
The Bushmaster
Headspace gauges for .45 ACP? Maybe if you are shooting compitition. Other then that.........Ppphhhtt!!!

EVERY round, factory or handload, that I use for home/self defense goes into the headspace gage. Having "seen the elephant" on several occasions this step gives me one less thing to worry about and more confidence in my equipment.

And, yes, the same thing goes for competition ammo.

Walkalong
August 8, 2009, 10:51 AM
I agree that for ammo you may have to defend your life with it would not be a bad idea to gauge it.

I am like The Bushmaster though, I don't for do it for .45. If your stuff is set up right, your rounds will work unless there is a gross error.

I also would not use a tight match chambered gun for self defense. ;)

I can not argue with anyone who gauges every single round. There is nothing wrong with that. Probably smart actually.

I wonder if they gauge factory ammo as well. Factory stuff is not immune to problems either.

rcmodel
August 8, 2009, 12:21 PM
how does the extractor come into play?As far as head-spacing goes, it doesn't, unless the case is excessively short.

There must be quite a bit of extractor hook clearance when the gun is in battery, or there wouldn't be enough clearance for the cartridge rim to slide under the hook at an angle during feeding while the barrel is dropped down out of battery.

The main thing the extractor does on an auto pistol is control the empty case and keep it on the breach-face long enough for it to hit the ejector. It also provides the pivot point to rotate the case out of the gun after it hits the ejector.

It actually plays a very small role in "extraction", as the case would likely blow out of the chamber on it's own if the extractor wasn't there.

Beretta & Taurus actually makes some blow-back operated pistols that have no extractor at all.

rc

ranger335v
August 8, 2009, 01:55 PM
OAL has got to be the biggest confusion factor in loading for newbies, and lots of older hands too. Basically, load to a length that feeds from your magazine and chambers properly. That's IT!

What we read is the books is ONLY what the people who made the book used in THEIR firearm with THEIR BULLET to produce THEIR RESULTS.

All the book cautions against changing ANYTHING in their components or dimensions is NOT due to SAAMI, or any safety reasons at all. It's simply legalise to give them some protection from idiots who get careless and then sues the book makers for the results when they blows their hands off. Fact is, there is no other single eliment in the total load data that offers as much potential for change as the firearm it is used in and no one ever mentions that! WE must load so our cartriges function correctly in our guns, not theirs. Thus, book OAL is NOT "SAAMI" for a specific bullet nor is it a rule we have to slavishly follow or blow ourselves up. Find your own best OAL and don't sweat it.

I wish they could print that and relieve some minds, but considerning the silly law-suit happy nation we have become, it seems they can't do that.

vagabond1
August 8, 2009, 03:56 PM
Help!! My 1911 GI Expert works great with commercial ammo, but my reloads are either stove piping or not locking the slide back on last shot.

jim

rcmodel
August 8, 2009, 04:46 PM
O'K.

You already have one thread running where you ask this question.

http://www.thehighroad.org/showthread.php?t=467522

Until you tell us what bullet weight you are using, nobody can begin to help you.

rc

NoAlibi
August 10, 2009, 01:34 PM
NoAlibi
Head space gauges are cheap and it's the best way to go.

This is the MidwayUSA auto pistol gage set I was referring to:

http://www.thehighroad.org/attachment.php?attachmentid=103111&stc=1&d=1249926131

I tried to find this on their web site so I could pass it on to anyone who might be interested. Not having any luck, I called them and I was advised that they no longer offered them (They couldn't give a reason why). When I went back to check for individual gages I was in shock that the price for one gage is ths SAME as I paid for the set (6 gages) on sale 15 years ago! :eek:

Did I say, "cheap"? Hoo-boy!!! My most grieveous error - sorry.

Yeah, I realize that things go up in 15 years, but not by a factor of 6!!! :fire:

Just count me as another grumpy old man. ;)

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