9mm Trimming question

[Rizzo]

Yes, I have read many threads about 9mm case trimming and the consensus from most reloaders is that they do not trim pistol caliber cases.

But........,

Since the 9mm case headspaces from the case mouth, the way I see it is for a batch of untrimmed 9mm cases that have been reloaded to a certain C.O.A.L, the length of the bullet from the case mouth will vary due to the different case lengths.

If we are trying to use a cast boolit then we set the boolit depth deeper, step by step, until it passes the 'Plunk Test".

But, since the cases vary in length, the next round set at that C.O.A.L. may not pass the plunk test due to a shorter case that was loaded and set to the desired C.O.A.L.. This would be because there is more boolit sticking out of the case and thus hitting the "rifling" in the barrel.

To avoid this potential problem trimming the 9mm cases to the same case length would solve this potential problem.

Does this make sense?...or, where am I going wrong with this thinking?

[JeffG]

Personally, I trim mine. I was seeing and feeling differences in crimp. Fortunately, I haven't needed to do it often.

[triggerhappy243]

the case does headspace on the case mouth. so the brass should be all the same length.... regardless of what you use as a bullet. As far as head spacing goes, the length of the protruding boolit is irrelevant to headspacing. if the boolit hits the rifling before it headspaces, your boolit is too long. trimming the brass any shorter will not fix the problem. You also need to be aware of that the boolit could make the brass case swell beyond acceptable dimensions..... making that round fail the plunk test.

[tazman]

Yes, I have read many threads about 9mm case trimming and the consensus from most reloaders is that they do not trim pistol caliber cases.

But........,

Since the 9mm case headspaces from the case mouth, the way I see it is for a batch of untrimmed 9mm cases that have been reloaded to a certain C.O.A.L, the length of the bullet from the case mouth will vary due to the different case lengths.

If we are trying to use a cast boolit then we set the boolit depth deeper, step by step, until it passes the 'Plunk Test".

But, since the cases vary in length, the next round set at that C.O.A.L. may not pass the plunk test due to a shorter case that was loaded and set to the desired C.O.A.L.. This would be because there is more boolit sticking out of the case and thus hitting the "rifling" in the barrel.

To avoid this potential problem trimming the 9mm cases to the same case length would solve this potential problem.

Does this make sense?...or, where am I going wrong with this thinking?


The situation you describe is possible but easily avoided.
I have never seen an unloaded/fired case that was too long to chamber. Being straight walled(slight taper),they will only shorten after repeated use, not lengthen as bottleneck cases do. If you stop the seating depth with the longest length possible, theoretically you could load a shorter case with the same OAL and hit the rifling with the boolit. What I do is load my boolits to a depth slightly deeper than the max OAL. That few thousandths is enough to make sure that short cases will still fit in the chamber.
All the 9mm pistols I know of have enough firing pin stroke to set off a primer that is chambered with slightly excessive headspace. If reliable function is what you are looking for, what I described is what you need to do. If maximum accuracy is what you are after, then trim away and discard cases as they shorten.

[dragonrider]

All I can say is do not waste your time.

[Char-Gar]

A uniform case length, is important to a uniform bullet seating depth in the case crimp, which in turn is important to a uniform bullet pull, which in turn is important to unformed pressure and accuracy.

Now the question is, just how important is ultimate accuracy to the shooter?

If the answer is not much, than any old mixed range brass will do just fine.

If the answer is somewhat, then sort brass by headstamp.

If the answer is very much, then sort brass by headstamp and length, which can be by measurement or trimming.

The 9mm cases seem to have much great length variation than most other handgun cases.

I would agree that case trimming is a PITA, and whether it is worth it or not, depends on your accuracy goals. Functional ammo can be put together will some pretty sloppy case length uniformity.

[Tackleberry41]

I never really messed with trimming 9mm, 40, 45ACP. For general purpose ammo not really needed. Now my blackhawk with the conversion cylinder, running 45 super, yea I put that little extra effort into it. Or new brass, will it work out of the bag, generally it does. But I don't buy new 9mm or 40 or 45ACP. My 44 mag rifle, or 45 colts, yea I trim them, as said you get way more consistent loading that way.

[bangerjim]

If a 9 is too long, it goes in the scrap bin! Not worth messing with those little dudes. I have over 9K of them, but even if I didn't, I still would not mess with trimming.

Same with 40's.

They are everywhere at the range for the picking.

banger

[Scharfschuetze]

Char Gar makes excellent points in his post above.

I might also add that you consider the accuracy level of your pistol. My Browning High-Power benefits from paying attention to all the loading details. My Glock and Beretta, not so much.

Neck tension will also play a part in uniform bullet release on ignition, so in addition to uniform length, make sure your cases are uniform (ie. same brand & headstamp) in this regard.

Uniformity usually equates to more accurate loads and better results in most of what we do in life, so articulate what your end goal is, be honest about what your equipment and your components can do and then load to a goal you are satisfied with and one that your equipment will reach without frustration.

[bedbugbilly]

For me . . . trimming 9mm brass wouldn't be worth it. First, I can't shoot that good . . . second, I'd just loose it on the ground and not be able to recover all of it making it not worth my time. I have a stash of about 7,000 K . . all range brass and mixed head stamps. For my shooting . . . not worth the time to sort it even. If they plunk in my cartridge gauge the way they should, they should be just fine.

But reloading and shooting means different things to different people . . . some concentrate on the "right alloy" while others concentrate on "bullet design" and others on "brass". If a person thinks they need to trim their 9mm (or other caliber) brass . . . then "have at it". With time spent on casting, loading, etc. . . . I spend enough time just getting stuff loaded to shoot let alone all the other things in life that need attention . . . and I'm so old, my time is limited so I've learned to spend my time on the "important" things . . . like having an extra coffee in the morning and taking a nap once in a while. :-)

[Ed_Shot]

All my 9MM brass is range-pick-up and bet I have 15K +. I have measured every case and it's separated by headstamp. I discard brass shorter than .747 and keep everything longer just to insure I get adequate expansion so there is no shaved lead during seating. 9MM brass that's only .740 long is not uncommon and I find the worst offender for short brass is Winchester. I don't measure or separate .380, 40 SW, or 45 ACP cases but I find it worth it with 9MM.

[dudel]

The few times I've gotten new pistol brass, it needed trimming for consistency.

[Harry O]

I wondered about the same thing quite a few years ago. So I decided to try a test. Trim a bunch of them at the maximum length and do some group-size testing with them against random cases. The maximum case length is supposed to be 0.754" with a trim-to length of 0.744" or 0.750" depending on the loading manual. I started measuring my cases. NONE of them were over length. Very few of them were over 0.750". Quite a few were under 0.744". That sort of killed my first idea. I did not have any long ones to trim-to-length.

A short while later I found some 9x21mm empty cases on a gunshow table and they were cheap enough to ruin. The experiment was back on. I set up the trimmer and trimmed them to 0.754". I loaded up a hundred or so and tried groups of 10 shots from a rest. 50 were shot from a Browning P-35 and 50 from a CZ-75 compact. Then I did the same thing with random length cases. The bullet, powder, and primer was the same for both.

The full length trimmed cases were definitely more accurate. They gave groups of about 2/3 the size of the unsorted brass. However, I did not think that the work needed to get that result was worth it. Keep in mind that NONE of the 9x19mm cases were long enough to trim and I did not want to use the wrong headstamps in my 9mm's. I still have some of the cases in a labeled bag, though.

[wv109323]

A pistolsmith in Hawaii that builds some of the most respected and accurate 1911's says that case length and brand is meaningless. His experience told him that the base of a cast bullet contributed more than anything to accuracy. The edge of the base of the bullet needed to be consistent(flat base or beveled base) and the sprue could not be "torn" when cut.
His guns most always shot under 2" at fifty yards many were better.
He loaded ammo by the five gallon bucket.

[Bullwolf]

Yes, I have read many threads about 9mm case trimming and the consensus from most reloaders is that they do not trim pistol caliber cases.

But........,

Since the 9mm case headspaces from the case mouth, the way I see it is for a batch of untrimmed 9mm cases that have been reloaded to a certain C.O.A.L, the length of the bullet from the case mouth will vary due to the different case lengths.

If we are trying to use a cast boolit then we set the boolit depth deeper, step by step, until it passes the 'Plunk Test".

But, since the cases vary in length, the next round set at that C.O.A.L. may not pass the plunk test due to a shorter case that was loaded and set to the desired C.O.A.L.. This would be because there is more boolit sticking out of the case and thus hitting the "rifling" in the barrel.

To avoid this potential problem trimming the 9mm cases to the same case length would solve this potential problem.

Does this make sense?...or, where am I going wrong with this thinking?


I think the part you are missing, is that no matter how much you trim (or don't trim) the case... The measurement you are looking at is the total overall length of the cartridge.

The length of your case does not affect the cartridges over all length while seating boolits, your seating die adjustments do.

*Boolits simply get seated out farther on shorter cases, and deeper on long ones*

However, the length of your cases will affect the amount of crimp you apply to each cartridge, unless you adjust your dies for each different length case.

Take a closer look at the plunk test.


http://castboolits.gunloads.com/attachment.php?attachmentid=114719&d=1391328588

You don't want your cartridges to head space below the barrel hood, and alternatively you don't want the cartridge to be proud of (above) the barrel hood either

What you are generally trying to do with the plunk test is set your OAL so that your boolit is not actually contacting the beginning of the rifling transition in your barrel.

https://lh5.googleusercontent.com/-dScRenzwZzE/Tz3NEksXtcI/AAAAAAAADOU/_pS6NKuOtrU/w860-h645-no/Bullet+Shapes.jpg

You also don't want to set your OAL so short that cartridges fall to far into the chamber.

By plunking loaded ammunition, you are also are assuring yourself that all of your reloaded cartridges will fit in your barrel. Case bulges, or boolits that are not seated straight will rub and may possibly bind up during plunking showing you that there is a problem before you get to the range and tie up your firearm.

Shootingtimes.com has a very good article that helps explain how to diagnose chambering problems while using the plunk test. If you don't quite grasp how it works yet, the article below is a good read. It also describes how to perform basic trouble shooting steps while using the plunk test.

http://www.shootingtimes.com/reloading/reloading-tips-the-plunk-test/


For the record I do not trim 9mm. I would discard a problem case before I ever bothered, and I own a case trimmer. I've loaded mixed head stamp 9mm commercially without ever having to trim a single 9mm case. I would never say that trimming 9mm is a requirement, but if you personally want to do it for consistency sake well there's nothing wrong with doing that either.



- Bullwolf

[mongoose33]

As a practical matter, a too-short case will "headspace" on the extractor; it's not going to fall in, and as long as the bullet is seated short enough that it doesn't contact the rifling, it's going to be fine.

Normally I just use a mix of brass for 9mm but I'm sure that if I worked at it I could tighten those groups. I shoot a lot of steel so 1" group accuracy isn't very important.

I don't sort or trim my 9mm brass; I probably should. I have 600 new Lapua 9mm cases I've yet to fool with, but now I'm going to be motivated to both trim (if necessary) and use them and see what I get. I'm sure they'll be better; might end up being so much better that I look at the 2000 rounds I just loaded out of mixed range brass and sigh. :)

[flyingrhino]

All I can say is do not waste your time.

+1 on that. I've been reloading and shooting 9mm for over 30 years. I have never had to trim one.

[swheeler]

COAL is NOT going to vary because of different brass lengths. The distance from your shell holder(cartridge head) to contact on seater plug is the same distance no matter what length your brass is. I have never found 9 or 45 brass that is longer than max length, ever. No I don't trim them.

[Char-Gar]

COAL is NOT going to vary because of different brass lengths. The distance from your shell holder(cartridge head) to contact on seater plug is the same distance no matter what length your brass is. I have never found 9 or 45 brass that is longer than max length, ever. No I don't trim them.

Longer than max length is not the issue. Uniform length is the issue.

[gray wolf]

As a practical matter, a too-short case will "head space" on the extractor;

Please don't tell me that 1911 handguns also do this.
Now I don't no for sure about different 9MM guns, but most extractors have enough wiggle room for and aft to let a case go forward a little.
Along with a firing pin that is long enough to push the round forward, so while the extractor holds it, the firing pin will push it forward when fired
so the case mouth is head spacing correctly.

Again, 1911,s work this way, So I am not saying that all 9mills do the same.

Took me a long time to grasp this, wasn't until it was correctly explained that I finally got it.

All my SWC bullets have the case head even with the back of the barrel hood, this is done by letting the bullet come to rest at the start of the barrel lead.

I would guess that if you drop the 9MM cases into a barrel that has been taken out of the gun-----very few case heads would be at the back of the barrel hood.
If they fall below then they are to short, so what are you gaining by trimming ? and how is this a fix ?

I do trim pistol brass if a nice even crimp is what I want, and most times I do.

What am I missing ??

[zomby woof]

I can shoot 9mm in my 38 super. It headspaces on the extractor. From what I understand, the first 1911's in 38 super did the same.

[Char-Gar]

Gray Wolf... The 1911 extractor will hold the case until stuck by the firing pin. It will then go forward until restricted by the inside rear of the extractor and there it will stop. That may or may not bring the mouth of the case in contact with the front of the chamber to headspace. There are some rounds that are so short, that they will not do so. Now this situation is not conducive to accuracy, but the rounds will fire and the pistol function.

The firing pin strike won't strip the rim from the extractor on a 1911 pistol. There are so many kinds and varieties of 9mm pistol, that I really can't speak to how those operate.

Trimming for uniform case length has nothing to do with headspace. As you correctly stated, bullet seating is the key to uniform overall length of the round. However with cases of unequal length, the amount and location of the crimp will change. This in turn has an effect on uniform pressure, which will show up in the accuracy of the round.

Functional ammo can be loaded with mixed make and length cases, but I am talking about maximum accuracy, where small things make a difference. For most folks they don't make enough difference to warrant the extra work of trimming, for some they do.

[Rizzo]

From reading the replies and article link posted, the scenario I described can be avoided by doing the following:

"If you stop the seating depth with the longest length possible, theoretically you could load a shorter case with the same OAL and hit the rifling with the boolit. What I do is load my boolits to a depth slightly deeper than the max OAL. That few thousandths is enough to make sure that short cases will still fit in the chamber." (thanks tazman)

and,
From: http://www.shootingtimes.com/reloading/reloading-tips-the-plunk-test/#ixzz3qRk6vdUd
"For pistol ammo, a general rule of thumb is to seat the bullet at least 0.010 inches deeper than the minimum depth required to fit."

I did some measurement testing yesterday and sampled 15-20 fired 9mm Luger cases and found the case lengths to be .740" - .745".
I then resized them and re-measured and found the cases to increase in length to a range of .7495" - .751".
Pretty interesting and a fairly uniform case length!

BTW, I had purchased a Lee 9mm trimmer and while it is adjustable in .001" steps the max length it trimmed to was only .740".
That seems a little short to me but would give consistency.

At this point I am not going to trim the cases and am going to use the methods described in my quotes above.

Thank you all for your input.

[gray wolf]

Here is a very good old post about head spacing,
to long to copy it over but well worth the Re-read.

http://castboolits.gunloads.com/archive/index.php/t-69593.html

It kind of shows how people can be wrong And be right as long as they are flexible in there ability to understand what's being said.

[Char-Gar]

The term "headspacing" is one of those terms thrown around without a common understanding of what it is.

My understanding is that headspace is the distance from the bolt face of the firearm and the place in the chamber where the case can move no farther.

In a rimless rifle case, this is the distance between the bolt face and where the case shoulder contacts the chamber.

In a rimmed rifle case, this is the distance between the bolt face and the place where the rim contacts the chamber.

In a revolver, this is the distance between the rear frame flat and the end of the cylinder, unless the cylinder is countersunk.

Now to the auto pistol, my understanding of headspace is the distance between the breech face and the shelf in the front of the chamber which presents the case from moving forward beyond that point.

In my understanding , a 45 ACP cannot headspace on the extractor as it is not part of the chamber, although it will keep the round from moving forward, so the firing in can ingnite the primer.

If the understanding of headspace is the distance between the breech face and "whatever" holds the case for the firing pin to ignite the primer, then a round 1911 round can headspace on the extractor.

It all depends on what an individuals understanding of headspace is. Without a common understanding, then the wheel goes round and rounds with opinions and so forth. I am certain there must be some technical definition of headspace that is used in the industry, but I don't know what it is. If somebody can come up with that, I will modify my understanding to conform to industry standards. That said, please dont give me a paraphrase or a recollection, I would like book, page and quote.

[gray wolf]

now to the auto pistol, my understanding of head space is the distance between the breech face and the shelf in the front of the chamber which presents the case from moving forward beyond that point. i have to agree with you, the term head space is one that is widely throne around without the true understanding of the term. But i think more involved is how the correct head space is achieved. Setting up a 1911 for the proper head space involves a lot more than dropping a round in the barrel and having the case head even with the barrel hood.



in my understanding , a 45 acp cannot headspace on the extractor i believe that to be true as it is not part of the chamber, although it will keep the round from moving forward, yes it keeps the round from going forward within the limits of the free space built into the extractor so the firing in can ingnite the primer. agree again, ever notice how much the firing pin can protrude through the breach face. the pistol was made to work within min. And max. Cartridge lengths.



if the understanding of headspace is the distance between the breech face and "whatever" holds the case for the firing pin to ignite the primer, then a round 1911 round can headspace on the extractor, it may be captive by the extractor hook, but to say this is allowing proper head space i believe is wrong. i think again in this case we miss the full understanding of head space in the 1911. A 1911 correctly set up for head space does not depended on an extractor and how or how it does not hold a case. Take some 1911 cases and drop them into a removed barrel, how many fit so the case head is even with the hood ? Don't know about your cases but many of mine have grown shorter from reloading and fall below the barrel hood. They do not contact the back of the breach face, yes they are being held by the extractor hook, but to say head space is being achieve because of this brings us to your statement about how the term is miss used and or not fully understood. With that i certainly agree. .[/quote]




1911tuner

january 11, 2006, 07:25 pm

in light of realizing that so many good folks are misinformed on the subject of correct headspacing in the 1911 pistol, i took the liberty of doin' this thread in the interest of our continuing education, so that all may be armed with the knowledge to make a call of: "sheepdip!" whenever some gunshop
commando drops a round into a barrel chamber...shows that the rear of the rim is flush with the face of the hood...and pronounces it good to go. While that condition may well exist in a pistol with perfectly acceptable headspace,
that, in and of itself, is not an indication.

Headspace falls into two categories.

Static headspace is the measurement between the breechface and the cartridge stop shoulder with the pistol in battery. Static headspace only changes with wear and/or locking lug deformation or setback...or wear on the breechface.

Live...or working headspace is the difference between that measurement and the length of the cartridge case that is fired in the gun...and varies with every shot unless all brass is trimmed to exactly the same length.

Excessive headspace is defined as static headspace that falls outside of acceptable limits as set by the saami for the caliber. Static headspace is correctly determined with a gauge...typically go and no-go. Precisely measuring headpace requires a determination of the exact dimension, usually done by using a go gauge and an appropriate feeler gauge in conjunction.
Go...plus feeler gauge thickness equals total static headspace.

Headspace limit for the 1911 pistol is .898 inch minimum and .920 maximum. Go and no-go sets are made to these specifications.

Headspace can be excessive and still be safe. It can be excessive and be dangerous. It depends on which direction that the excess goes.

If the stop shoulder is reamed too deep in the chamber, it can be outside ot the maximum limit, yet still be safe. If the locking lugs are incorrectly located,
incorrectly cut, or deformed...the excess can be dangerous , because it allows partial opening of the breech on firing. The case backs out of the chamber until the slide reaches the limit of its rearward travel as determined by the horizontal lug to lug fit...and the case head loses chamber support.

You can ream the chamber too far...file the hood to perfectly flush with a chambered round or go gauge...and it will look like good headspace...but it's not.

You can ream the chamber perfectly at minimum dimension...with a cartridge
or go gauge dead flush with the hood face...and if the lug fit allows the breech to partially open beyond no-go limits on firing, you have a dangerously excessive headspace condition.

To better understand this, we need to understand that when the pistol fires, the slide and barrel are tied together by the horizontal lug engagement. The barrel is slammed forward by the bullet while the thrust of the expanding gasses are driving the slide rearward in a 20,000 psi tug of war...and are doing their level best to separate the slide and barrel. If the lugs allow the slide to move rearward beyond safe limits...no-go...the case follows the breechface...loses chamber support at 6 o'clock...and bulges or blows.

[Char-Gar]

Well, I read that piece from 2006 and did not find it particularly helpful. It seems to create two types and definitions of headspace i.e. static and live. While my understanding would agree with the "static" understanding, the "lives" seems a little bizarre to me. In my understanding he is just talking about poor barrel lug to slide fit allows the slide to unlock from the barrel in a premature manner.

This "live" headspace thing seem no more valid that folks taking about the round headspacing on the extractor. I am not a tech guy, so maybe I am wrong.

At any rate, the few things to which I won't apply technical terms are;

1. Seating the bullet to allow the loaded round to almost touch the breech face is a good idea as long as the round chambers and fits in the magazine.

2. In will over a quarter million 45 acp rounds loaded in fired in a score or more 1911 pistol, I have never had a bulged or blow case.

3. All this picking around over tech talk is pretty much a waste of time. It is pretty much a word game. I know how to load safe and accurate ammo for the 1911 pistol regardless of what is called what.

[Larry Gibson]

All I can say is do not waste your time.

+1.

Larry Gibson