First I have to say I’m not expert in reloading, but the length the case expands too is going to be control some what by the size of the chamber of the gun that it is being fired from. Along with how hot the load is and how many times the brass case has been used. Even to what type of die you used to size the brass with can affect the flow of the brass. Some brands of case will even last longer than others. I reload a lot of .223 and I trim my brass every time I size it. And I generally only use the case two times before I throw them a way. Because I’m not sure how many times the cases have really been used. I usually load my .223 at about 90 percent of what the max load calls out for. And I’ve only been able to get about 4 reloading though brand new rifle cases for .223. With pistol rounds I just keep using the cases until the case splits down the neck. My pistol ammo is also only load to about 90 percent of max loads because I shot a lot and do not feel its worth hammering a gun to death with hot loads.
It is not incorrect. It is just not a complete thought and process. If you measure brass expansion after firing, I would bet that you would find that it expands out a bunch but not much in length. But that outward expansion needs to be pushed back in to the correct size so when you size it, that pushes the brass back in and like a tube of toothpaste you squeeze, that forces material to the ends as the path of least resistance.
So the firing of the case and brass expansion leads to the necessity to resize. Since the firing cause the brass to change shape. When it is resized, that expanded brass becomes elongated brass.
Mark this is the first I have ever heard of this approach. I am curious does this cause you any problems when seating the new bullet since the mouth is not open as much? Thanks
First, you have to understand what causes the case to lengthen is brass flow. The thickest part of the case that contains the powder is the web which is at the base of the case, nearest the primer. As the case expands under pressure, brass flows forward as that’s the path of least resistance. The case grows thinner at the web and thicker forward of the web and makes it’s way to the neck. Eventually, the web develops a groove from the thinning and stretching and will separate there. Re-sizing the cases does not reverse the brass flow, so the case gets longer.
markm, be careful just neck sizing your brass without the neck expander. If the brass gets too thick at the neck, when the bullet is seated, the neck diameter of the case will be too large for the neck diameter of the chamber. This can cause dangerous spikes in pressure
Interesting notion… I’ll have to think on that one for a bit. I’m doubtful it’d be a problem for me since I only load brass twice… But I still want to wrap my head around that idea.
I can’t say with certainty, but I believe the whole “brass flow” concept is bogus. What I do know is that the majority of brass length increases come during resizing. It’s as someone stated previously – the case dimensions are displaced forward as the body is squeezed down in the resizer. The case stretches at the web, but I don’t buy into the notion that brass turns plastic or liquid momentarily and then flows fwd.
Markm, have you taken measurements on case growth both w/expander ball and w/o? If so, what are the deltas? Did you lube the inside of your case necks at all or were they dry?
If you adjust your resizer to bump the shoulder just a couple of thousandths from a fired case dimension, you’ll controll how much stretch/case growth you experience. If on the other hand you just screw die in to press until firm shellholder contact is achieved, you can end up bumping shoulders .006 - .008", and you most certainly will see excess stretching and ultimately, casehead separation. You can even test a few cases by taking a paper clip or a short section of bailing wire, bending the tip to 90 degress, and filing it sharp. Then see if you can snag the separation ring that might be forming – no snagging, you’re GTG. But if you feel the snag, realize that brass is at end of life and further reloads are unadvisable.
Mistwolf, how does utilization of an expander ball keep neck thicknesses in check, while omitting the use of an exp ball allow them to thicken?
mistwolf has it right…the brass will stretch the most depending on the where the case & chamber vary on the saami spec.
The tightest chamber one the fattest case will stretch much less than the vice-a-verca. You can watch this by how much you have to trim after every fl. This is a GOOD brass life indicator!!
I have gone to minimal full length on all my reloading after the br boys started doing it and winning…auto guns get the complete full length and tossed after 3-4 hot loads.
I just did a quick check on doing a full length resize on my press. It gave me a increase in length of .004-.005 on 10 differient pieces of brass.
On a related note measuring some range pick-up brass showed an overall length of varying between 1.48-1.52. Given the maximum length allowed is 1.760 it doesn’t seem you need to trim each time.
I’ve found that as long as the interior of the necks are lubed, case stretch is minimal. That’s using diluted Lee lube w/alcohol sprayed on cases in a ziploc and kneaded a la “shake and bake”. Enough lube makes it into the interiors to lube them.
While I haven’t made any effort to compare results, I’ve heard (and adjusted my dies accordingly) that if you adjust the sizer ball up high in the die, just below the neck, so that expanding takes place while the neck is still partially in the neck resizing portion of the die, runout is reduced compared to when the ball is positioned low in the die and the neck clears this portion before it’s run over the expander. When thus adjusted runout measures between .000 - .002" IIRC. Just something to ponder…
The neck sizer squeezes the outside neck diameter down. Neck material gets thicker, and brass is work hardened, mostly on the outside. Neck expander increases internal neck diameter. Material gets thinner, but as it’s pressed against the previously cold worked outer layer, it flows forward more. That’s why cases lengthen more when both are used.
I don’t make the claim that outside neck sizing only is bad practice. The whole purpose to sizing the neck is to get adequate and consistent tension on the seated bullet. For the average reloader, using an expander after sizing the neck is the easiest way to achieve this. When neck sizing without the expander, if all the brass has the same thickness and that thickness is right for the sizer and bullet, all is good. If the neck thickness varies, tension will vary and so will pressure and velocity and accuracy will suffer. (If the reloader is getting the accuracy wanted, there are no worries.)
Here is a quote from Varmint Al’s website, an engineer who knows more about reloading than I ever will- “Most cartridge cases have a limited life because of high stress levels and the plastic deformations of the brass during firing and resizing.”
Well, after resizing…it is what it is. If the brass is too long, you need to trim.
Why?
When an overlength case is chambered, the mouth or edge of the neck will come up against the throat (left, top) before the bolt has fully closed or the case shoulder has contacted the chamber (left, upper middle). The camming action of the bolt is so powerful that it will actually crimp the case mouth fully into the bullet (left, lower middle) and wedge the case so solidly between the bullet and the throat that the neck cannot expand to release the bullet. Chamber pressures in this situation can and most certainly will go dangerously high (left, bottom).
I’ve found that 5.56 brass ends up being longer than .223 brass, I guess that makes sense based upon the difference between .223 & 5.56.
I’ve found a good number of the brass that I’ve tried are actully shorter than the recommended trim length. For “blasting” loads I just load them without trimming.
I’ve recently started trimming by Lake City brass to 1.760 Vs 1.750 and seem to get better results from my Noveske SS barrel.