How much length does a case gain in the sizing die?

snowman · Sep 8, 2021

May be impossible to answer with any degree of certainty. Nevertheless I hear repeatedly both here and elsewhere that the only stupid question is the one that's not asked -so there it is.

Here may be some helpful information. I'm getting ready to load all my .44mag Starline cases the second time(bought them new and loaded & fired them all myself, with the same load and in the same gun). I really like the brass, but there is some significant variation in case length, and all are shorter than the standard length given in the reloading manuals of 1.280(from .009 to .017 shorter in their fired condition).

What I would like to do is trim them to the same length before sizing, in order to obtain a reasonably consistent crimp(not a perfectionist -just would like more consistency this time around). But I don't want them too short either, and don't know how short is too short. I know that the compression in the sizing die lengthens them, but I don't know how much.

Thought some experts here might be able to provide some enlightenment.

By the way, these are for long-range target work/fun in a 629 DX. Using a full charge of H110 under a 210gr JHP.

As always, many thanks for your time, friends.
Andy

WR Moore · Sep 8, 2021

Case length growth-actually stretching-varies widely according to how much the brass is stretched during firing and the following resizing. And a bunch of other factors. As a result all the trimming instructions I've ever read are to trim AFTER resizing as that's the condition it'll be in when you go to seat the bullet. Right out of the forming dies, there's going to be some variation in case length, especially of straight wall rimmed cases where the headspace is controlled by the rim. Frankly, I've got some .44 brass that's near the 50 year mark and the one time I tried trimming, very few cases needed it.

FWIW, I measured some new, never loaded/fired .308 match brass and found each example was either at or near the listed trim length of 2.05 in. Out of curiousity I ran a couple of cases through a sizing die. The case body didn't seem to touch the die, the neck did. One pass through the sizing die and expanding the neck grew the cases almost exactly 0.005 inches. But that's a bottleneck catridge.

If you just gotta do something, I'd suggest running the cases through the sizing die and set your trim length at the specified 1.275 in. What needs trimmed gets trimmed, what doesn't ignore. Methinks you're over thinking this. A handgun isn't a bench rest rifle.

Imissedagain · Sep 8, 2021

Size then trim to spec.
The ones less than 1.285" can be trimmed to be equal as well to make the roll crimps consistent.

Measure the cases before sizing and then after to get an average.

I treated my eyes and time remaining to a good set of digital calipers not long ago.
The new little digital, Mitutoyo 500 series, for our loading chores and the old big one is for the Iowa's crew..

teletech · Sep 9, 2021

How much does it rain in a storm?
As others have said, you can't predict it with any accuracy. Case shape, the cleanliness of the brass and dies, so many factors. I've even seen some cases get shorter in sizing.

ReloadforFun · Sep 9, 2021

As was mentioned, size, then trim. At that point the firing/shortening, sizing/lengthening should not present problems for a straight wall case.

Bottle-neck cases are the ones that grow in length when fired due to the pressure flowing brass from the shoulder to the neck.

Mike SC Hunter · Sep 9, 2021

I have in over 45 years of reloading never trimmed a pistol or revolver case. I do on bottle necked rifle cartridges.

BLUEDOT37 · Sep 9, 2021

snowman said:
...case length, and all are shorter than the standard length given in the reloading manuals of 1.280(from .009 to .017 shorter in their fired condition).

Fired cases are shorter because the case has expanded & the case walls are bowed out.

Once you size them, & straighten the case walls out, the change in the measured length is proportionally longer to the difference which varies with the load's pressure & the chamber it was fired in.

Size the cases first, then trim them.

If needed, reduce the diameter of your trimmer's pilot to fit the sized case.

.

stansdds · Sep 9, 2021

Straight wall cases stretch very little to nothing at all. I will trim revolver brass once, never had to trim it again. I once trimmed hundreds of 45 ACP cases, chasing best accuracy for USPSA competition loads. I don't think I really gained anything in that effort and all the brass was eventually lost in matches. In big matches, you were not allowed to police your brass, that was payment for the services of the range officers.

Bottle neck cases are a different story. Typically, the case neck will stretch as the case comes out of the die, the expander ball swages the case neck against the die and that will stretch the brass.

dla · Sep 9, 2021

This doesn't answer your question, but if you used the Lee FCD for your crimping, the case length wouldn't matter.

jem102 · Sep 9, 2021

BLUEDOT37 said:
Fired cases are shorter because the case has expanded & the case walls are bowed out.

Once you size them, & straighten the case walls out, the change in the measured length is proportionally longer to the difference which varies with the load's pressure & the chamber it was fired in.

Size the cases first, then trim them.

If needed, reduce the diameter of your trimmer's pilot to fit the sized case.

.

The above is what I believe you will find correct depending on what you are trying to accomplish.
It would be an easy step this next time out to "group" the various case lengths, within reason, reset the crimp for each batch and test them on paper by overlaying a fresh target for each case length group dead on top of the previous target. Radical crimp variation can cause accuracy issues but as already stated by others not a deal breaker in the vast majority of cases. when you peal down to the first target I think you will pleasantly surprised to find the overall mass group to be quite consistent with no outliers that would cause a poor hit unless you "pulled" that particular shot so make notes as you go round by round. This should reassure you of the "no trim needed". Having said all this "I" enjoy my handloading and do not find it a chore to trim my cases when I start to see the case mouths are rolling into the groove too high on the wheel gun as I have determined the max COL with a 10 case average when the brass was once fired with a given bullet. When "plunk" testing for the auto if the rim is past flush with the hood I will knock a few thous off that lot.

mikld · Sep 9, 2021

I would think there are several factors involved with brass growth. Age of case, number of times reloaded pressures, and gun used. I started reloading 44 Magnum in the late '80s and have 5 guns chambered for the cartridge. Heavy loads in my Puma stretch cases a lot and sizing them makes them a bit longer. My Dan Wesson had "tight chambers" and growth is less, minimal.

Don't overthink this phenonium. I don't trim my 44 cases and get good consistent crimps (Lee collet crimp and Redding profile crimp), good to very good accuracy, especially from my DW 44H, and consistent neck tenison for good consistent ignition. 44 Magnum is one of my favorite cartridges and have reloaded everything from 123 gr. balls to 300 gr ingot "T-Rex Killers" for my 5, 44 Magnums.

But a lot of reloaders trim their revolver brass and no harm, no foul, the Reloading Police isn't going to raid your shop and confiscate your handloads. They are your cases, your guns, your time, so if you wanna, trim them...

Tim357 · Sep 9, 2021

I've not had pistol brass grow that i remember. Generally, bottleneck rifle cases grow as they are dragged over the expander ball. Straight wall pistol brass doesnt get dragged over an expander ball, it is pushed into an expander. If anything, pistol brass tends to shorten over time, or at least stretching is held to a minimun. YMMV

snowman · Sep 10, 2021

Gentlemen,

I'm tied up for several days and am unable to respond. I should be able to get back on the forum on Monday. Thanks to all for your responses.

Regards,
Andy

67tempest · Sep 10, 2021

I have been reloading the same .44 mag brass for close to 40 years and have never had to trim it. I use a very moderate powder charge and I'm not shooting for pin point accuracy, just blasting.

44wheelman · Sep 10, 2021

Psi, chamber size, resizing die diameter, brass alloy….uuhhhg, many variables.

I also shoot a more moderate load, and after initial trimming, keep all my brass lots together, and don’t have much issue with crimping. But lead is a little more forgiving than jacketed (with respect to crimping).

gwpercle · Sep 10, 2021

Straight walled handgun brass stretch little or none after their first firing . I get a batch of new - once fired brass ... trim them all to a consistent book "trim to length"...usually between minimum and maximum ... and then reload that batch untill they wear out ...

Lets call it ... trim em' once and be done with it .
Gary

mikld · Sep 10, 2021

Tim357 said:
I've not had pistol brass grow that i remember. Generally, bottleneck rifle cases grow as they are dragged over the expander ball. Straight wall pistol brass doesnt get dragged over an expander ball, it is pushed into an expander. If anything, pistol brass tends to shorten over time, or at least stretching is held to a minimun. YMMV

Any time a brass tune is swaged, it will lengthen. Sizing (aka swaging) does not remove metal, it just dislaces (moves) it. On a straight walled case the easiest place for the metal to move to is toward the mouth, thus making he case grow in length... "Metal Working 101"

Or at least when I size any of my 9 different caliber handgun cases...

SMSgt · Sep 10, 2021

I'm not sure why anyone would be concerned about the length of a case before resizing.

snowman · Sep 12, 2021

Thanks to all for your time.

My curiosity got the best of me and I did a little exercise/experiment to see what kind of answer it might give me. As the pictures show, I chose 20 fired cases at random, measured the length of each and recorded it on a post-it note, then sized the case and measured it again.

Every case, with one exception, stretched from .007 to .008(the exception stretched .009). This is the answer to my question. For those who didn't think that straight-wall pistol cases stretched, I don't know what to tell you. My dial caliper, though not top of the line, I've found to be accurate whenever I've used it.

I was struck somewhat by the consistency of the stretch, since one or two of you mentioned that there would be a large variation, which I expected also. All but one were within .001 of each other.

I discovered that the variation in length between unsized cases, with one exception, was only .003 or less. Seventeen of those were within .002 of each other. I was mistaken in my initial post indicating that there was significant variation in the case lengths. All, however, are at least .007 to .010 short of standard .44mag length, after resizing.

Some are wondering the rhyme and reason behind my question(and this little experiment). It's virtually impossible to adequately explain, but trimming cases after resizing, in my particular setup, is somewhat problematic and definitely inconvenient. There are ways around the issue, but none are very satisfactory in my estimation. I realize that trimming after sizing is the better, and standard way of doing it.

Fortunately, given the surprising consistency of case lengths both before and after sizing has convinced me not to trim the cases. A couple thousandths or so won't cause any problem with crimp. I will be chamfering and reaming the case mouths, which I didn't do when they were new; and this caused some rough travel thru the sizing die and a little difficulty seating the bullets.

Thanks again, friends. Hope this post was reasonably clear.

Regards,
Andy

WR Moore · Sep 13, 2021

One minor quibble with your last post: your definitiion of case stretch. Case stretch is a permanent change in case length caused by brass flow. A good example is some .308 brass that's supposed to be 2.015 inch maximum OAL. I had some sized brass (reloaded 5-6 times) that run over length by up to 0.025 inches. What you described is the change in length caused by reducing the outside diameter of the fired case by swaging the case back to unfired diameter. The brass itself isn't stretching, it's just changing shape.

How much length does a case gain in the sizing die?

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