Home Forums Hunting & Shooting Ask The Gunwriters Handloader article: Cartridge Expansion

I hope you and Eileen will also consider publishing a collection of the first five years of Rifle Loony News next year. There's a lot of entertaining reading as well as good info and it would be mighty handy to have it bound into one place!

Agree. Too many articles just seem to not carry the in-depth descriptions of the subject today,

WOW!, Has it been 5 years already?

count me among those who appreciate more detailed, lengthy, well researched, discussion of such topics.

msquared,

That's an interesting idea. I'll bring it up with the CEO of Deep Creek Press.

Plus 1 on a compilation of Rifle Loony News.

Steve

Glad to hear the RLN compilation idea is going to the top for consideration! I would definitely order and I'm sure others would too.

The initial reaction from the CEO is very positive. She's sure it could be out by this spring.

You know what they say about opinions. Well I have mine too.

We have read that CHE is not a good tool for the handloader. Then we read CHE can only be used on new brass. I say one should either ascribe to CHE as one of the valid tools in the handloaders toolbox, or not. Middle ground is for politicians and liars.

I use CHE when loading for strong modern rifles, among many other tools, including pressure-tested data published by reputable sources. I don't claim any of them tell me the absolute pressure of my loads in my rifles. But the one thing CHE does tell me is that brass in the case head is flowing and expanding. I consider any measure of that an indicator that pressure is higher than I want to shoot, so I back down to where CHE is non-existant. On a remarkably regular and repeatable basis, CHE appears at one certain point as I increase the powder charge in increments, and likewise disappears when I back down to the previous step where it did not appear on the way up. That load at the point just below CHE is the the first load I shoot for group, and 9 times out of 10 it shoots well enough for me. It is important to note that I do not exceed published maximum loads even if CHE is not present. If the published max shows no CHE, that is the first load I shoot for group, and I only go downward from there if performance is not acceptable, which is rare. At the outset I only load powders that are appropriate for the caliber, so success is likely.

You have read that CHE measurement can only be performed on new brass cases. I say that not only should it be performed on once-fired cases, but it MUST be performed on once-fired cases. New cases vary greatly in the amount they expand on the first firing. I have measured initial CHE from zero to .005" (yes, five thousandths of an inch). New cases must be initially fired to get initial CHE out of the equation. Only then does measurment of expansion of the solid case head have meaning. Anyone who uses CHE knows that the diameter of the case head tapers larger as the distance from the extraction groove increases and the instrument gets farther away from the solid case head and up into the area of the hollow case body. The hollow case body is NOT what we are trying to measure. We want to measure expansion of the SOLID case head. All cases expand in the body, that is how they are supposed to work, but expansion of the SOLID head is what we are interested in here.

You have read that case brass varies in hardness, and thus in the pressure at which CHE occurs, and that is true. However, BRASS IS STILL BRASS. Comparing brass cases of differing hardness is not akin to comparing brass to steel. It is still brass, and it will behave like brass. Will softer cases expand a LITTLE earlier than harder cases? Sure they will, but again, we are using brass here, not brass and steel. Also, as I mentioned, CHE is only ONE of the tools used to indicate HIGHER PRESSURE THAN I WANT TO SHOOT.

Lower pressure cartridges are a completely different story. We should never load 30-30, 45 Colt, or 44-40 cartridges anywhere near where CHE occurs. In these cartridges I rely solely on pressure-tested data published by reputable sources. I won't say I never ever exceed published data for these cartridges by just a little bit, but CHE occurs at pressures far above what these rifles and cases are designed to hold, so CHE should never be seen in these rounds.

I guess everyone has me on ignore....

Mike

ready,

Sorry about that. I have a hardcopy subscription and reveived 288 better than a week ago, maybe two.

Hmmm that is odd used to get the e-edition a week or so before the paper, must be a ploy to entice the expensive paper edition subscriptions.

Thanks,

Mike

Mule Deer
I go more by the chrono than CHE, mostly because it's easier for me to measure and I don't have to worry about the difference in hardness from one lot of brass to another.

The problem is, how do I know my chrono is reliable as far as giving me a true number? What I do is shoot a factory load and use that velocity as a baseline, even if it is off from what the manufacturer lists. My reloads are indexed to the factory velocity over my chrono on that particular day. I have no way of knowing if the numbers I'm getting are true, but figure like numbers in factory and reloads should give like pressure, more or less.

Have you done a thorough review of chronos on the market to determine their accuracy and consistency?

Muledeer I just read the article and learn and enjoy very much from your articles. With that said please be gentle but by using the chrony are you saying that the speed can be used to gauge where pressure is at? If say an 06 load 165 is around 2700 fps this would imply you could significantly add more powder? Thank you and I would by a CD with your articles.....

I'm sure that I'm one of many who will line up for that.
And this.

Kodiakisland,

I trust a chronograph far more than case-head expansion as well, partly because obtaining meaningful CHE is comparatively difficult.

My main chronohraph is an Oehler 35P, which most people consider the very best available for handloaders, since it's more tolerant of varying light conditions and does't "drop" shots.

But I have compared several less expensive chronographs to the Oehler's performance, by setting them up in line and shooting the same bullets over both. So far the winner is the ProChrono. Not only are its velocities very close, but it's picked up fast .17 bullets in the same poor light conditions, and misses fewer shots than the other inexpensive chronographs I've tested. I tested the basic "Pal" model, which retails for right around $100, and liked it so much I just bought another. (A gun writer can't have too many chronographs....)

The most reliable way to use a chronograph to work up handloads to safe pressures is to compare published data with the same powder and bullet you're using to your results. If your barrel length is different than the test barrel's, adjust the published velocity by adding or subtracting 25 fps per inch.

As an example, let's say you're using 130-grain Nosler Partitions and H4831SC in the .270 Winchester. The Nosler manual lists a maximum load of 59.0 grains for 130-grain bullets at 3124 fps from a 24" barrel. Let's say your barrel is 22", so you subtract 50 fps from 3124, for 3074 fps. This means that at about 3075 fps in your rifle, the pressure should be safe, even if the powder charge you end up with is a grain or maybe even two higher.

Of course, if the load shows obvious signs of high pressure before you reach 3075 fps, then you should stop. But that rarely happens when using this method, though it has occurred a few times with a soft batch of brass.

That would be absolutely fantastic! Of course, I would still push for some sort of general comparison of (at least the most common) different bullets and their relative effect on pressure.

Great stuff! Thanks as always for sharing your knowledge and testing!

Mule Deer, For the average handloader like me the question has always been when to stop increasing the powder charge when working up a load. I own an F1 Chrony and take advantage of it to compare to factory ammo velocity or published data as far as velocity goes when working up a load.

What has helped me the most in the past few years is to use the Hodgdon published data for my rifle loads. As an example, by using the top load of LeverEvolution data with 30-30 load with a 170 Sierra FN bullet, I'm at 34,000 cup according to Hodgdon.

My 30-06 load is using a 180 grain Sierra bullet with the top load of H4831sc, I'm at 44,000 cup using Hodgdon's data. Both these loads I listed shoot well in my rifles, and I use the components exactly as listed by Hodgdon to avoid any possible extreme increase in pressure.

This take a lot of the guess work out of overpressuring my rifles while still getting a decent velocity. I do realize others do like experimenting while working up loads and are quite qualified to do so. I am just happy to use these loads and take a lot of the guess work out of the equation for me.........

That's certainly a valid way to do it, and you'll almost never encounter problems.

But many handloaders like to get as much zip as possible, even though another 100 fps doesn't usually make any practical difference. In my experience a chronograph is a very good tool for that, far better than the old methods of pressure guessing.