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.




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.



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/reloadi...he-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 ??