Home Forums Hunting & Shooting Ask The Gunwriters Great article in the new Handloader Mag by MD!

I've read about the merits of case head expansion for many years. A couple of years ago I did a test of approximately 60 rounds of 30-06, all loaded with the same powder, bullet, primer, etc in virgin Winchester cases. The charge weight was varied to give pressure readings from approximately 25K to 90K in a SAAMI spec barrel fired in an universal receiver. For each shot, two pressures were recorded with two conformal piezo transducers per SAAMI, one pressure was recorded with a case-mouth piezo transducers per NATO, and two pressures were recorded with two independent strain gage systems. They agreed within expectations.

I wanted to do a properly documented article on the use of case expansion as a means of pressure measurement. Each case was carefully saved and marked to correspond to a particular shot. After the test was over, I attempted to measure the fired cases to determine expansion. I found no significant expansion until we reached the proof pressure range. The cases were thrown into the scrap bucket, and I didn't write the article.

KenO

Montana Man, I know you and I don't prescribe 100% to Hagel's load development but at least its a good text book and resource on how to do it. 31 pages of it and a lot more detail than I care to go through on every new load I work up!

I doubt Hagel, Keith, O'conner, or John Wayne cared about "caveats" on their statements. There is a volume of good wisdom in "Guns, Loads, & Hunting tips",even if we discount some of his "He Man Methods" regarding pressure. We can learn a lot from these ol'e boys!

Ken,

How much was the "significant" expansion at the proof pressure level?

MM

Ken that is fascinating and I think that article needs to be printed. Have you seen Steigers study? If not I could scan it and send it over. Obviously he didn't have your same technology back then with piezo transducers at the time so he used a copper crusher barrel and a .206 piston.
Thanks for responding!

Speer #10 lists loads for the .30-06 using MRP with a CCI 250. With a 60.0 gr charge weight and a 180 gr bullet in WW brass, the velocity was 2644 fps out of a 22" M700. MRP was the powder that took N205's place in the Norma lineup, which, according to Hercules, is the same as RL-22, i.e. MRP=RL-22. If you look on the can/jug of RL-22, you'll see "Made in Sweden" on the bottom of the label.

You're recording 200 fps more with less powder, which seems like a lot, even with the extra 2" of barrel. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

Nice to have you joining us now and then Ken.

Now if I could come up with more than 1 of the 4 things you mentioned were required to revive the 35.

Sorry, I can't give exact numbers on the observed case expansion. It should suffice to say that the cases were trashed because I judged that the effort was hopeless in terms of finding a way of observing pressure before it got well past the suggested maximums. Someone else with instrumentation (not copper) will have to do the study.

Just my opinion ---

KenO

I did a similar test for HANDLOADER magazine a few years ago. This involved three cartridges, the .22 Hornet, .270 WCF and .30-06.

In the Hornet the "expansion ring" in front of the rim was measured (essentially the method Ken Waters has long used); in the .270 and .30-06 the case head was measured the same way Hagel did it. Then the loads worked up were tested on the piezo equipment at the Western Powders lab in Miles City, Montana.

The Hornet loads were warmer than SAAMI standards, but not dangerously so. The .30-06 loads were right at SAAMI standards. The .270 loads were close to 70,000 psi.

Along with other incidents (such as the one in an earlier post on this thread, where two different brands of belted magnum brass produced .0004" and .002" head expansion with the same manual-listed load) this pretty much convinced me that measuring brass expansion was not a consistent way to estimate pressure--and any inconsistency in estimating pressure is a bad thing!

JB

Sounds like the only truly safe way to handload is to never exceed book maximum with a given combination of components, and when changing anything(i.e., primer, case, bullet) to start over with the lowest listed loads.
This leads me to another question-If I am at the books listed maximum, and I see no "signs" of overpressure other than a slightly higher chronograph reading, should I back it down a grain or two? My specific example being a swift 225grain AFrame out of a 340wby using the max. Swift manual charge of 93.0grains, which I worked up from starting- No visible signs of overpressure other than my chronograph gives me about 100 fps faster than the manual says??

I believe that in the field, John's article confirms much of my own experience. To me it puts a more technical face on why my 7mm-08/ 7x57, .35 Whelen, .257 Rbts, and 180 gr. .30-06 just seem to kill with much more authority than the paper ballistics would suggest. I am learning to be happy with that 2700-2800 fps area (2500 in the Whelen) and just go hunting.

I could be wrong here , but any testing done by working up loads in sporting rifles(by head expansion or any other method) and then taking pressure readings from piezo equipment.........in COMPLETELY different barrels and chambers (I assume) would be more or less meaningless.

Just because the 270 loads(for example) were a bit over the top in the pressure barrel , does NOT mean they were in the sporting rifle............

Agreed, but my test of the 30-06 was in the same barrel.
KenO

Now we're starting to see the truth, that ALL published loading data is basically of little value. The published data was safe in that particular barrel/chamber and there is no assurance it is safe in any other barrel/chamber. We just assume it is safe and it may or may not be a good assumption for our particular application.

That then throws the velocities achieved into the same light. It was achieved in a barrel/chamber with a particular load that produced that pressure with no assurance it can be duplicated in any other barrel/chamber.

When I look at the freebies handed out by the powder companies, I see "Accurate 2003 Reloader's GUIDE, Reloader's GUIDE for Hercules Smokeless Powder, IMR Smokeless Powder Reloader's GUIDE. They are guides to what was safe in their equipment and it is then left up to the reloader to determine if it is safe in his equipment. Think it isn't so, read the disclaimers in each one of them and see what they actually guarantee!

I don't know just why you are so surprised. All the loading manuals, free or otherwise, simply report what the writer observed. They are offered to handloaders as guidance only. For you to consider them as the gospel truth of what you will get with your loads in your gun is well beyond their intent. You can't safely regard them as predictors of what you will get. If you handload for your gun, you are on your own.

If load receipes were consistent and predictable, the ammo factories would not spend a large portion of their budgets simply testing ammo they've just loaded. Even the "reference ammo" that is often considered a known pressure is not a pressure calibration standard; it's main function is to establish a mythical "average" barrel when all the test barrels are made to the same specs.

Perhaps you now understand what Mule Deer and others have been saying when they state that velocity in excess of factory quotes is the first and most reliable indicator that the pressures are in excess of factory pressures. There is no free lunch, and with the same powder, you don't get extra velocity without extra pressure.

Regarding your earlier argument regarding the revisions in the pressure specs for 357 Mag ammo, I expect that the original specs were done with copper crusher in accordance with the SAAMI CUP procedure. Copper crushers used in the 30K - 40K psi range with the CUP procedure are extremely fickle. The crusher reading depends not only on the peak pressure, but can be significantly influenced by powder burning rate, piston mass and lubrication, and the shear strength of the case wall. It is no surprise that the initial standards needed revision after experience.

KenO

Ken,

You realize with the program available, someone is being responded to, but that response may not actually directed toward you. I really wasn't "picking" on you with my response, I was just using the "quick reply" feature.

However, I really appreciate you taking the time to respond!

In the science disciplines I am familar with, there is a high degree of accuracy. The abilities to weigh objects to less than .1 mg have been in place since the very early 1900s, with the advent of the Chain-o-Matic analytical balance. Man made elements that produce molecules that can be counted on one hand have been around since the 1930s. To think pressure measurements are still in the dark ages, is beyond anything I can comprehend!

I have already referenced the UK's National Pressure Laboratory (NPL) and the methodology employed that utilizes "distortion effects". There shouldn't be any fickleness to the measurement of distortion effects in a copper pellet. Surely there's an ASTM protocol for testing ballistic pressures that should return repeatable results.

From the appearance, it seems the lack of precision somewhere, is prohibiting the determination of proper quantitative results. A minimum SAAMI sized chamber with a minimum sized cartridge should return a particular result, with consideration for the tolerances allowable in production powder.

When thousands of dollars are expended in equipment to ensure the USP chemicals in your potato chips don't have more than 1 ppm of Pb in them, to expect less than stellar quality control from powder pressure testing is totally unacceptable.

We both know it isn't exactly true when you say, "There is no free lunch, and with the same powder, you don't get extra velocity without extra pressure." There are things that can be done that will reduce friction and result in more velocity with the same amount of powder. I know I'm being nit picky there, and please understand I didn't call you a liar, which would have been rude, crude and socially unacceptable, but science is in the business of picking nits all the time. <img src="/ubbthreads/images/graemlins/wink.gif" alt="" />

Just so you don't have to ask, I am familiar with the primary, secondary and tertiary products involved in the production of nitro cellulose. I also understand the variation involved through the use of natural sources of cellulose. Most organic reactions are anything but straight forward and have plenty of by-products. I used to make a living in the production of organic chemicals and their testing.

Paul,

I understand that you have vast scientific experience.

How much time and effort have you actually spent actually measuring chamber pressures in firearms?

There are SAAMI/ASTM manuals available regarding ammo testing. Have you read them?

Let's not talk about what might be done, or what is theoretically possible, but what actually can be done and at least demonstrated if not proven.

KenO

The velocity figures that your chronograph gives you may not be accurate.

If your screens aren't quite as far apart as the distance that your chronograph is set for, you'll get higher velocity numbers at SAAMI-safe pressures � but your bullets aren't going as fast as those figures tell you that they are. Conversely, if they're too far apart, and you keep increasing your powder charges to get the velocities that you see in a manual, you're stomping on thin ice � with pressures that may stomp back, sooner or later (when your hardware gets tired of tolerating the abuse).

'Way back in the days before Everyman computers, I calculated the velocity errors for several erroneous spacings. Lost that old table years ago, so I've been planning to redo it someday. When I do it again, I'll publish it. Calculating all those numbers is a chore that daunts this ol' math ignoranus. Right now, I can't even guess how big an error in spacing makes a worrisome error in the fallacious "velocity."

Be sure that your screens are fully and only as far apart � as accurately as you can measure the spacing � to get accurate velocity figures.

Only the mental image is left of an old photo that I saved for years, then lost along the way � a chintzy chronograph's instructions on how to set-up your screens � with the screens mounted on two steel posts that you stomped into the ground at approximately the set spacing. At a distance that you measured by stepping it off? I suppose. That's the impression that I got � not nearly good enough unless you can step-off distances to a very small fraction of an inch.

Measure the correct spacing to within whatever error is congenital in your steel tape � with no slack or sag in the tape. Then mark that spacing as precisely as you can mark it � with a scriber, not a Marks-a-Lot felt-tip pen � on a length of PVC pipe, electrical conduit, or aluminum angle � something that's both straight and rigid, preferably that you can fasten your screens to, accurately and repeatedly if not permanently.

And don't expect your velocity figures to match published figures to within less than 25 ft/sec or even less than 50 ft/sec.

340Boy--

As Ken points out, your chronograph might not be accurate--but I have owned a bunch of them and found they were all within 30 fps of each other, if set up properly.

I probably would back down your load a little. Swift bullets are notorious for being "grabby," due to their copper jackets and soft cores. They thus tend to create more pressure than bullets of the same diameter and weight, which is why the Swift data for various cartridge/powder/bullet combos is often less than listed in other manuals.

JB

Thank you Mule Deer,
That was my understanding of the Aframes as well, I will take your advice.
Regards

Paul,

Yes, I know that MRP & RL22 are both made by the same mfg. in Sweden, however, IME, they are NOT exactly the same.

I still have quite a bit of MRP and save it for certain cartridges (namely 270 Win & 338) and if you compare the kernels side by side both by unaided eye and with magnification, you will see that MRP is darker and shinier and the kernels are much more uniform in size than with RL22. They are both double based propellants.

In using both of them, I have always felt that RL22 seems to act a bit faster than MRP and consequently, where I have used them both in the same gun, I am usually a grain or two light on max charges of '22 vs MRP.

I like MRP better than '22 and in my personal testing MRP is very temperature stable; never tested '22 for temp stability but have seen conflicting reports on it here as well as reports of somewhat high velocity spreads between lots.....again, I have not see that with it.

As for MRP, replacing N-205, not sure that was the case; for a while both were offered at the same time.

Regarding my 'o6 loads w/ 180 gr. bullets, the cases are usable for multiple loading and seem just fine in my gun.........what are your comments on the marine's loads? Those are HOTTTT by my standards.

MM