Help with 9mm Headspace

[tding]

:confused:I'm having trouble understanding headspace with my 9mm loads. Some of you may be tempted to tell me that I'm close enough but I'm a perfectionist.

I'm using an RCBS 9mm-124-RN mold with wheelweights. I have tried sizing to 355 and 356 seating to a COL of 1.140. According to my Dillon 9mm headspace gage I'm .0010 off.

I have checked the trim to length and try the sized case in the gage before loading. It seats in the gage just fine before the boolet is loaded. I'm sure the problem is with the boolet but I don't know how to adjust other than buying a 354 sizing die.

Can someone shed some light on headspacing in general and perhaps offer some suggestions - - other than "stop being so anal"?

[oneokie]

Will your loaded rounds chamber in your pistol? Can you extract the loaded round easily? After extracting the loaded round, do you see rifling marks on any part of the boolit? or the mouth of the case? Bright spots on the case mouth? or anywhere on the case?

Headspacing=the distance from the breech face to the place in the chamber that stops forward movement of the cartridge.

[GabbyM]

not sure how the Dillon gage is cut. But if it has a throat the bullet may be hitting that bfore the case is tight. 1.140 is fairly long.

Also any 9mm except a match chamered gun is going to have lots of room for fat cases. So I would not jump at going to small with your bullet. Remove the barrel from your pistol and try the round in it's chamber. most 9mm's shoot best with .357" bullets.

[clintsfolly]

my bet is your not taper crimping or you need to taper crimp more clint

[HeavyMetal]

Not really enough info here to decide what your issue is.

Are you having feeding problems? Or is this one of those "the guage" says it wrong things?

Bear in mind you don't shoot a guage!

Tell us a little more about the problem and you'll get help thats for sure!

[gray wolf]

delete

[mike in co]

ok so i will get up om my soap box.
headspace is a characteristic of a gun, bolt and chamber create a number called headspace.
ammo is not headspace......most ammo is built to a CLEARANCE of the chamber. sometimes the oal is ZERO clearance(boolit touching the lands), other times there is tons of CLEARANCE....most pistols.

OTHER than that, we have no idea what you are talking about. do you want an oal of 1.140 ?
is 1.140 too long for your gage ? is 1.140 too long for your gun ?
is your gage set for castboolits ? size the bullet for your gun( 1 to 2 thou over), set oal to chamber and feed.

do not undersize your boolits to make some imaginary oal from a book.

mike in co

[dwtim]

As an aside, why would you want the bullet touching the rifling on a 9mm autoloader? Not only would that effect pressure, but it would probably introduce feeding problems. It would on my pistols, anyway.

The 9x19 headspaces on the case mouth, which means taper crimp only. The case length standard is 0.754".

How to measure headspace:
http://www.forsterproducts.com/Pages/gages.asp

[mike in co]

As an aside, why would you want the bullet touching the rifling on a 9mm autoloader? Not only would that effect pressure, but it would probably introduce feeding problems. It would on my pistols, anyway.

The 9x19 headspaces on the case mouth, which means taper crimp only. The case length standard is 0.754".

How to measure headspace:
http://www.forsterproducts.com/Pages/gages.asp

i own the only 9mm that actually headspaces on the case mouth. the chamber was cut so that a certain lenght brass actually was at the chamber mouth.

most guns are nowhere near the brass end. that is a design criteria, not a fact of life.
most guns chamber on the extractor.

nothing wrong with a pistol round that touches the lands, one that tries to jam would be silly.

specs are nice, facts are often different.

mike in co

[Harry O]

Just to throw more confusion into the thread.

Has anyone here done any measuring of 9mm Luger (or Parabellum) cases? The max OAL is supposed to be 0.754". However, I have NEVER found a 9mm case that long. The longest I have found (and this is after measuring abut 500 and sorting them) is 0.750". The average is about 0.745". For something that is supposed to headspace on the mouth (or front) of the case, this would seem to be VERY bad for accuracy.

Someone on another forum once pointed out that when he used only the longest cases, the accuracy was better. I did all my measuring after that and tried it. He was right. The group size was about 2/3 as large for 0.748"-0.750" cases vs 0.740"-0.745" cases (both loaded with the same powder, charge, bullet, and OAL).

Unfortunately, I have never found where I could buy 0.754" long 9mm Luger cases, so I bought 500 9x21 cases and shortened them to 0.752"-0.754". I have tried them and the group size is about half what I was getting before with random lengths.

I also tried seating bullets out far enough to reach the rifling and headspace there, but they were too long, so I did not shoot them.

[mike in co]

Just to throw more confusion into the thread.

Has anyone here done any measuring of 9mm Luger (or Parabellum) cases? The max OAL is supposed to be 0.754". However, I have NEVER found a 9mm case that long. The longest I have found (and this is after measuring abut 500 and sorting them) is 0.750". The average is about 0.745". For something that is supposed to headspace on the mouth (or front) of the case, this would seem to be VERY bad for accuracy.

Someone on another forum once pointed out that when he used only the longest cases, the accuracy was better. I did all my measuring after that and tried it. He was right. The group size was about 2/3 as large for 0.748"-0.750" cases vs 0.740"-0.745" cases (both loaded with the same powder, charge, bullet, and OAL).

Unfortunately, I have never found where I could buy 0.754" long 9mm Luger cases, so I bought 500 9x21 cases and shortened them to 0.752"-0.754". I have tried them and the group size is about half what I was getting before with random lengths.

I also tried seating bullets out far enough to reach the rifling and headspace there, but they were too long, so I did not shoot them.


i shorten the chamber on one of my 9mm to .750...for just the above reasons. brass trimed to this length.
yep facts are different than specs....

[dwtim]

The headspace in your gun is what it is. There is no force that compels manufacturers to exactly follow industry standards. The SAAMI-recommended maximum case length for 9x19 is .754". I've seen trim-to length recommendations from .745" upward. Actual sampled cases are all over the map. Since chambers and cases may vary, reference headspace for a particular chambering is expressed as a tolerance and not an exact figure.

I realize that a properly dimensioned extractor will fit snugly in the cannelure and control the cartridge--I should hope it would; that's the point of an extractor, right?. Obviously an incorrectly cut extractor would create problems, but the distance from the far end of the chamber to the bolt face is still the critical dimension.

If I had custom-made 9mm brass cut to .850", my gun would be out of battery, and no amount of extractor work would fix the insufficient headspace. If I trimmed the case to .635", any extractor with a sufficiently strong spring would simply push the cartridge into the chamber without passing over the rim and into the extractor cannelure. No amount of extractor work would fix this, either, as the excess headspace would be so great that the firing pin would simply dent the primer--if it made contact at all.

Look guys, I'm sorry, but I didn't originally post to get in an argument about "extractor headspacing"; I posted in the hopes that the originator of the thread would read the page. It is not clear from the original question whether his problem involves headspace or some problem measuring cartridge overall length.

[mike in co]

The headspace in your gun is what it is. There is no force that compels manufacturers to exactly follow industry standards. The SAAMI-recommended maximum case length for 9x19 is .754". I've seen trim-to length recommendations from .745" upward. Actual sampled cases are all over the map. Since chambers and cases may vary, reference headspace for a particular chambering is expressed as a tolerance and not an exact figure.

I realize that a properly dimensioned extractor will fit snugly in the cannelure and control the cartridge--I should hope it would; that's the point of an extractor, right?. Obviously an incorrectly cut extractor would create problems, but the distance from the far end of the chamber to the bolt face is still the critical dimension.

If I had custom-made 9mm brass cut to .850", my gun would be out of battery, and no amount of extractor work would fix the insufficient headspace. If I trimmed the case to .635", any extractor with a sufficiently strong spring would simply push the cartridge into the chamber without passing over the rim and into the extractor cannelure. No amount of extractor work would fix this, either, as the excess headspace would be so great that the firing pin would simply dent the primer--if it made contact at all.

Look guys, I'm sorry, but I didn't originally post to get in an argument about "extractor headspacing"; I posted in the hopes that the originator of the thread would read the page. It is not clear from the original question whether his problem involves headspace or some problem measuring cartridge overall length.


your extreme examples are completely out of place as that is not what is being discussed..chambering a round in a known gun. i would guess that we would disagree with the terminology on 9mm headspace. no chamber design only has a single number as its headspace dimension all are either a number plus a few thou, or a min max number as in the 9mm which is 0.754 min to 0.776 max. there is no tolerance. to be in spec it must be between these numbers. it is not written as 0.750+/-0.004...that would be a tolerance. again this is terminology. yes there is no law forcing a manufacture to build to saami, but failure to do so, means the possibility of failure to chamber commercial ammo, or failure to fire. any given gun has a single number as ITS HEADSPACE. knowing this number aloows one to custom build ammo for it.
but since we still do not know what the orginators issue is, all of this is just chatter.....
have a good day.

mike in co

[Echo]

Headspace seems to be what I am getting more of - intracranially...

[mpmarty]

tding, the gist of all these answers should boil down to:

Cast boolit use in semi auto pistols is NOT a science, it is an art.
Do not size the boolits down to .354 as you will not be happy with the outcome.
As stated, remove barrel and try dropping loaded rounds into the chamber. The rear surface of the case head should be flush with the barrel hood. If it requires a bit of thumb pressure to make it go "home" that's ok but it should not fall deeper into the chamber and it should not stand proud with gentle thumb pressure.

Don't get so wound up in the "scientific details" that you lose sight of your goals.

[StarMetal]

i own the only 9mm that actually headspaces on the case mouth. the chamber was cut so that a certain lenght brass actually was at the chamber mouth.

most guns are nowhere near the brass end. that is a design criteria, not a fact of life.
most guns chamber on the extractor.

nothing wrong with a pistol round that touches the lands, one that tries to jam would be silly.

specs are nice, facts are often different.

No you don't own the only 9mm that headspaces on the case mouth, I own one. It's a match 9mm barrel that I built an upper for on my 1911 Gold Cup. The only 9mm I've ever had that I actually had to trim cases.

mike in co


No you don't own the only 9mm that headspaces on the case mouth, I own one. It's a match 9mm barrel that I built an upper for on my 1911 Gold Cup. The only 9mm I've ever had that I actually had to trim cases.

About sizing. My groove on my match barrel is .3535 so I have to size the bullet so that it's no larger then .356 for it. In fact with certain brass .356 bullets won't chamber.

I don't believe it taper crimp dies being the solution to a lot of things. That's not the original way the 9mm or 45acp were originally intended to be crimped.

Just my two cents.

Joe

[Daves1]

Correct me if I'm wrong, but I thought all 9mm headspaced on the case mouth same as .45 acp's.

[anachronism]

Correct me if I'm wrong, but I thought all 9mm headspaced on the case mouth same as .45 acp's.

In theory? Perhaps. In practice? Not unless you order a custom barrel (in most cases). Most autoloading cartridges are held in place by the extractor, on often sloppily at that. There is such a wide divergence in chambering that uniformity is right out the window. In order for zero headspace to work, every case has to be the same length, with only a very small tolerance permitted. Every chamber has to be the same too. These things simply don't happen in todays manufacturing society. You can install custom barrels, with tight chambers, as mentioned above, then you get to trim sort & trim brass, & perform other tasks to assure uniformity.

You have to pay extra in todays "wham, bam, thank you M'am" manufacturing society for this level of precision, & most guys simply aren't willing to handload (not reload) to achieve this anyway.

Yup, the worlds a sloppy place...

[35remington]

"Most autoloading cartridges are held in place by the extractor, on often sloppily at that."


No, no, no, absolutely not. We kill this one, here and now.

Guys, this belief gets recirculated over and over and over again. It's generally (the vast majority of cases) quite wrong. In actuality, tolerances are held such that even a fairly well below minimum length case in a maximum chamber is still not headspacing on the extractor - because extractor clearance is greater than this. Tolerances are specc'd to avoid problems, not allow them.

Let me drive the dagger straight through the heart of this mistaken belief. I have a pretty renowned pistolsmith corroborating, by the way.

Here's an example.

Remove barrel and slide from your 1911 (one frequently mentioned as having high tolerance variation) leaving barrel in slide. Insert empty case under extractor and chamber the round, locking lugs in the slide.

Observe case rim position versus the extractor hook with the barrel in the slide and the lugs engaged . The rim is well away from the extractor hook because it's headspacing on the empty case mouth. You can even get cute and pry on the case rim to move it forward to make sure it's against the chamber shoulder.....and it's still away from the extractor hook. Extractor headspacing isn't occurring, unless you've got a very, very, very short case in 45 ACP.

Tolerances are such that this is generally AVOIDED as rim headspacing is so extremely undesirable (cushioned firing pin blow; case canting in the chamber; poor accuracy) that it is very much in the manufacturer's interest to prevent this from happening. "Tolerances" so often "blamed" for causing extractor headspacing actually see to it that it doesn't happen - the very great vast majority of the time. The military, and those making large runs of autoloading designs, set tolerance such that this does NOT happen....tolerances are used to prevent undesirable occurances, not facilitate them.

Believe me, in WW 2, the military knew what variations were possible in 1911 construction, and the extractor location and chamber depth are set by JMB and various manufacturers such that extractor headspacing is avoided the very great majority of the time.

Handloader magazine KILLED Charles Petty's assertion that autoloading cartridges headspace more often than not on the extractor. Brian Pearce pointed this out, with Scoville backing, in an article directly addressing "extractor headspacing" in autoloading pistols.

Charles Petty was forced to recant.

The "headspacing on the extractor more often than not" myth has been killed deader than a dodo.

You boys just ain't got the word yet.

Feel free to replicate the test.

Headspacing on the extractor as "a matter of course" ??? "Most autoloading cartridges"????

Afraid not.

Here's Petty's recant:
"Another writer took me to task over my statement from a previous column that the .45 ACP can't headspace on the case mouth because of the relative lengths of case and chamber. Much as I hate being wrong -- I was.

In the industry standards both maximum case length and minimum chamber depth are the same at .898, so while they don't meet, the rimless straight case can go into the chamber as far as it needs to reach the shoulder. My erroneous conclusion was based on the fact the extractor holds the rim, which is true. What I overlooked was the difference between the extractor hook width and the thickness of the rim. This dimension allows for normal variations of case length and lets the case mouth touch the shoulder. Now if we had a case that was markedly shorter than usual, the extractor would come into play, but the gun would still work."

Here's the link:
http://findarticles.com/p/articles/mi_m0BTT/is_165_27/ai_105698450

If, for some reason, your cases are headspacing on the extractor, find out what's wrong and fix it for it's not a normal occurrance and is to be avoided.

[mike in co]

"Most autoloading cartridges are held in place by the extractor, on often sloppily at that."


No, no, no, absolutely not. We kill this one, here and now.

If, for some reason, your cases are headspacing on the extractor, find out what's wrong and fix it for it's not a normal occurrance and is to be avoided.


lol what a joke .
it may be true in a 1911,,,but not in the rest of the guns.......

may i suggest you go do a search on this site under brass.....9 in a 40
i'm in the brass biz..i have almost every cross up in semi autos ....32's in 380, 380 in 9 and 40's, 40 in 45.....9 in 40......

i personally have shot 9mm in a 9x21 gun...fully functional..that is aprox 78 thou short of the chamber mouth.

you can claim all you want, those of us that actually custom build guns and ammo, know otherwise.

sorry you aint selling gun rag drivlle here.....

mike in co

[35remington]

Mike, you're not paying attention. And I'm not beholden to the gun mags, just correcting the mistaken impressions advanced here. "The extractor not headspacing" comments I have are when the right cartridge is used in the right gun.

I didn't say that the WRONG cartridge COULDN'T headspace on the extractor, as in 40 in 45, 9 in 40, etc, etc, as it can and does, as the visible proof shows of bulged cases.

Where you err is in assuming that the extractor headspaces the majority of the time when the correct cartridge (45 in 45, 9mm in 9mm) is fired in the correct chamber. It does not, clearly and demonstrably the vast majority of the time.

It can, and does, headspace on the case mouth the vast majority of the time when fired in the right chamber. (Or on the bullet if it contacts the leade). But not on the extractor.

"you can claim all you want, those of us that actually custom build guns and ammo, know otherwise."

Building a custom gun doesn't automatically make you a headspace expert, as Charles Petty built custom guns too and also got the "headspace on the extractor" thing wrong.
It's time to look at the right information regarding autoloading pistol cartridge headspace in the proper chamber.

Mike, the extractor does not headspace the round when the right cartridge is used in the right gun. The vast majority of the time. It is important that you understand the distinction, as you're comparing apples and oranges when talking about headspacing a 40 in a 45 by the extractor, or a 9mm in a 9X21. I don't understand why you're making this irrelevant point. It isn't germane to this discussion, as we're talking about using the right ammo in the right chamber.

[StarMetal]

35remington is right. Another thing that throws some people off is that the firing pin on the 1911 can have a long travel. One thing not mentioned is often, especially with lead/cast loads, the bullet shoulder headspaces the round. Not exactly the correct thing to do, but lots of reloaders do it.

Another thing brought to my attention about the 1911 is the firing pin stop. If you look at the current ones the bottom edge is rounded to easy camming the hammer back. I was told that this isn't the correct profile. See the weight of the slide, the recoil spring, and mainspring are what control the slide recoiling. I was total that the original firing pin stop had a less round profile and the reason being that it would require more effort to cam the hammer back which was all figured in the total scheme of 1911 slide control. Any comments here about this?

Joe

[fecmech]

There was a discussion on The High Road back some time ago on that subject. Early Bullseye "smiths" changed the profile on the stop to better handle the light loads used in Bullseye competition. Some pretty knowledgeable fellows over there on the .45 auto. JMB had it all figured into the equation, the stop profile, mainspring weight and recoil spring weight. They all have an effect, it's not just change the recoil spring.

[leftiye]

Youse guys sure can find thangs to argue about! What I don't see is why it isn't just left at "for each of these scenarios, bett your butte that there's a gun out there that functions in that way." Further, as has been stated, it would be sheer folly to consider that any but a very few guns were made precisely as they should be made. What should be has been outlined in several angles, what is - is what you've got to make your ammo fit. Therefore, if it will chamber, a cartridge assembled so that the boolit touches the rifling is the end-all of this discussion.

[UncleClark]

If your completed rounds do not drop completely into the case guage is could be that you need to apply a bit more taper crimp. I have had that problem with 45ACP and 9mm is similar.

You 'belled' the case mouth before you seated the bullet and unless you undo the bell it might not drop completely into the guage. I use those Dillon guages a lot and have found them quite usefull in helping to adjust the crimp.

Also make sure your guage is cleaned out - they can load up with gunk.

Hope this helps.

[tding]

Loaded 50 9mm's last night sized to .356. 47 out of 50 dropped right into the gage. The difference was using two seperate steps (seating then crimping) instead of trying to seat and crimp in one step. It appears that the boolet was being crimped in the one step process.

Still wish I understood the process better. Even tightening the crimp on the last 3 boolets they will not drop completely into the gage.

[dwtim]

I hate to impose, but it is possible to post a zoom pic of the cartridge that won't fit in the chamber gauge, and perhaps one inside of your calipers?

The problem I had with one-step seat and crimp in the 9x19 was lead shaving. The seat body on my RCBS die is pretty wide, so now I flare the case mouth slightly before seating. It works out because I always taper crimp my nines. (Well, okay, it is a problem because the case mouth work-hardens, but that takes a while.)

[MtGun44]

Are you taper crimping, or using a roll crimp?

In 45ACP tc is critical to proper cartridge fit in the chamber. I tc
my 9mms too, but have loaded FAR,FAR less 9mm than 45 ACP, and always
have tc'ed my 9mm, so not as sure about tc vs roll for the 9mm, but I would
recommend it as a general rule for all semi-auto pistol rounds.

I did load a whole lot of .38 super and it required a tc for reliable chamber fit.

Bill

[StarMetal]

Are you taper crimping, or using a roll crimp?

In 45ACP tc is critical to proper cartridge fit in the chamber. I tc
my 9mms too, but have loaded FAR,FAR less 9mm than 45 ACP, and always
have tc'ed my 9mm, so not as sure about tc vs roll for the 9mm, but I would
recommend it as a general rule for all semi-auto pistol rounds.

I did load a whole lot of .38 super and it required a tc for reliable chamber fit.

Bill

I tc nothing and have zero problems. I build a match upper in 9mm for my Gold Cup frame, as I mentioned before, and the match barrel has a very minimum chamber. First one I've ever had to trim my brass to fit. It would chamber any bullets larger then .354 I don't, yet it chambers perfect and without tc the rounds. All my tuned 45's also chamber perfet without a tc. In fact they chamber empties which you know aren't tc'ed.

I don't know, seems some people have to tc, but I never have. I sure would like to try your pistols sometimes...bet I can get them to chamber reliably without a tc.

Joe

[tding]

With apologies for the photography

[UncleClark]

It might be the diameter of that first band on the bullet that is showing. Is there any difference in diameter at that first band? Either that or the taper crimp. It looks like the round is not dropping in by about the height of that first band.

[dwtim]

Ah, thanks for the picture. Now I understand why you're sizing down the bullets. There is a noticeable stretching of the neck in the right hand example. How thick are those case walls?