- September 26, 2017 at 2:59 pm #47168
Loading Manual Error……
Over the years, especially the last nine years with an Oehler M43 actually pressure testing, I’ve discovered error in data in almost every make (Speer, Lyman, Hornady, Hodgdon and Nosler) of loading manuals. This is especially the case with data from older and newer manuals that list pressures derived from the C.U.P. method of testing. Lee’s manual simply copies the data from other sources, both C.U.P. data and modern psi data obtained from transducer/strain gauge pressure measurement. Many newer manuals have loads “adjusted”, usually down, from the data in older manuals. Many think this is from lawyers, etc. but the truth is most newer reloading manual data is derived from better and more complete pressure testing through the use of peizo-transducers and strain gauge measurements. What is found is many older loads that were thought to be within safe standards for the cartridge actually were too high in pressure.
A recent example has been found using H4350 in the 30-06 with Hornady’s new 178 gr ELD-X bullet. A friend of mine recently had goodsteel build him a long range rifle based on a M700 action. It has a 31” Palma contoured barrel with a 12” twist chambered in 30-06 XCB. Based on my previous experience with ’06 match rifles and long range rifles I suggested 4350 powder. He collected a good amount of all three flavors; IMR, Hodgdon and Accurate Arms. He also got a supple of 175 Sierra MKs and the new Hodgdon 178 ELD-X bullets. He is using Winchester match prepped cases and Federal 215 Match primers.
He decided to try the Hodgdon’s H4350 powder and turned to the Hodgdon #27 manual. One would assume Hodgdon had the data well tested and correct since it’s their powder. We were discussing the loads by phone (he is in NE Oregon and I’m in Arizona) so I opened up my Hodgdon #27 manual and turned to the data for the 30-06 with 180 gr bullets. The #27 manual lists the max load for 180 gr bullets using H4350 at 57.5 gr. That is with a C.U.P. of 49,200. The velocity listed from a 24” Winchester M70 barrel with a 10” twist at 2798 fps. I have not used H4350 in the 30-06 (I mostly use IMR and AA) so I took the data at face value.
My friend decided to work up from 54 gr in ½ gr increments to 57.5 gr of H4350. A few days later he called back just tickled pink as the 57.5 gr load was shooting right at ½ moa at 300 yards. He had broke down and bought the top end Chrony with printer but hadn’t yet chronographed it. I was up there a few weeks back on my way to the Tacoma area. We went out to the local range and set up the Chrony and chronographed the 57.5 gr load. There was no indication of excessive pressure; bolt opened normally, primers looked fine and no excessive expansion at the case head. But holy smokes…..the average velocity was 3060 fps!!!!! My prediction with either AA4350 or IMR4350 under a 175 gr Sierra MK was 2950 fps +/- given the 31” barrel……but 3060 fps? About 3 weeks later I returned back through there so we took the rifle up to another friend’s ranch where they have a 1000 yard range with a sturdy bench to shoot from. He put 9 shots consecutively into right at 1 moa at 1000 yards in a 5 -8 gusting to 10 mph side wind. I put 10 shots into 1.2 moa. Again, even though it was 80+ degrees there was no sign of excess pressure.
However, that night my friend was depriming the cases and three primers basically fell out of the pockets. The primer pockets were swollen and no longer would hold a primer. That was the first sign of excessive pressure. My friend gave me a pound of the H4350 and a box of the 178 ELD-Xs to bring home with me to pressure test that load. I have the Winchester cases and Federal 215 Match primers. When I got home I loaded test loads of 56.5, 57 and 57.5 gr. Yesterday morning at daylight I was at the range here in Lake Havasu to test those loads. Was 65 degrees so heat would not be a factor. My 30-06 test rifle is a M98 Mauser with a 24” barrel. I chambered it with a match reamer to minimal headspace. I gives pressure readings via the Oehler M43 that are commensurate with the known pressure of Federal and Winchester factory loads used as “reference ammunition”.
I shot a ten shot test with M72 Match to validate everything was set up correctly. The measured data was within normal range. I lightly cleaned the barrel and proceeded to test the 56.5 gr load. The test rounds were loaded in fire formed test Winchester cases NS’d with a Bonanza Bench rest NS die. Primers were Federal 215 Match. Powder charges were weighed with a Redding scale. The 178 ELD-Xs were seated to 3.330” which is just off the leade.
The Oehler M43 was set up to measure the pressure and velocity for each shot. Start screen was at 15 feet with a 4 foot screen spacing. Target was at 100 yards.
The 1st test shot went 2882 fps with 69,200 psi(M43)
The 2nd test shot went 2873 fps with 68,900 psi(M43)
The 3rd test shot went 2869 fps with 69,200 psi(M43)
I quit testing and did not fire the remaining 7 rounds of that load nor did I fire any of the heavier 57 and 57.5 gr loads. With the 69,000 psi +/- from the “start” load I sure wasn’t going any higher…….
Average for the 3 test shots was:
The M43 correction to muzzle velocity was 2884 fps. The 3 shots grouped .94”.
The 56.5 gr H4350 test load was 86 fps faster than the Hodgdon manual listed max load of 57.5 gr. Note the test barrels were both 24”. Obviously the psi of the 56.5 load was quite excessive. I hesitated to guess at the pressure of the 57.5 gr load but based on experience I’d guess it was 75,000 +/- psi….well into “proof level” loads.
On the return home I figured something was definitely amiss. I pulled the bullets of the cartridges not fired and reweighed the charges….they were spot on. I then looked at a couple burn rate charts and discovered my own “error”. H4350 is sandwiched right between AA4350 and IMR4350. My experience with both of those is that 56 gr is a max load (measured 60 – 62,000 psi) under a 180 gr Hornady SPBT. I then checked Hornady’s 8th and 10th Edition manuals. They list 55.3 gr H4350 as a max load under 178 – 180 gr bullets…….Hello……says I, there’s a 2.2 gr difference between the Hodgdon and Hornady manuals. The 2700 fps velocity level +/- is also commensurate with what I get out of my test rifle and M70 (24” barrels with 56 gr AA4350.
Examination of the fired cases revealed no sign of excessive pressure as shown here. They were fired left to right. The primers appear normal for a top end jacketed 30-06 load with 60,000 psi. 2nd photo shows the case as fired left to right with a fire formed case (far right) from a previous normal psi firing.
Again, no sign of excessive pressure, just normal expansion at the expansion ring after 3 firings.
I’ve reloaded up test strings of 54.5, 55.0 ,55.3, 55.6 and 55.9 H4350 with all other load parameters being the same. Hoping to test before the week is out. I will post the results here.
This is another example that care should be exercised when using older data, especially when the pressure is listed as measured with the C.U.P. method. One should always develop loads with a chronograph even if staying within manual data. This is an excellent example because if a velocity seems too good to be true it probably isn’t “too good”. It takes pressure to generate velocity so if you get more velocity than is expected or usual with a weight of bullet in a cartridge then odds are the pressure is high. The old notion that there are “fast barrels” giving 100 – 200 fps more velocity is a myth. With barrels made to tolerance and chambered properly they all will give just about the same velocity +/- within normal variation. I’ve been chronographing many different loads in many different firearms since ’74. I’ve been pressure testing numerous loads (milsurp, factory and reloads) in over 33 cartridges in multiple firearms the last 9 years and have yet to find a “fast barrel”. Yes I’ve found “fast loads” but they are always because of excessive pressure.
- September 26, 2017 at 5:41 pm #47172HarterParticipant
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That would tend to explain my claims of start data being way faster than the books .
Funny that this would rear it’s head with the 4350s .
It would also throw a wrench in the pressure curve clean up point of I4350 that I’ve used as a guide ……..
Good catch .
- September 26, 2017 at 8:20 pm #47175Rattlesnake CharlieParticipant
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Thanks Larry. I always try to get data from at least three different sources. If there is an outlier in there, I look for more sources. It gets tough with newly released bullets as the manufacturer probably is the only one with any “published” data. Your data also shows that the different flavors of 4350 are NOT as interchangeable as most would like to think. I sure wish the Ohler 43 pressure measuring system was still available for purchase. I missed the boat on that one.
- September 27, 2017 at 6:39 am #47178GoodsteelKeymaster
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That’s a brilliant word Larry, and explains some of what I have expected.
One thing that you might try doing is using the 180 SMK and see if pressure is lower?
- September 27, 2017 at 7:38 am #47179kensParticipant
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I have Hornady 3rd edition, and I always thought it was a ‘hot’ book.
it shows 56.4gr as top load. that’s where you showed 69,000 psi.
- September 27, 2017 at 11:37 am #47184
I believe that manual was publish “back in the day” when bolt lift, primer condition and case head expansion were the primary means recommended for a reloader to determine a “max” load. Wasn’t case head expansion measurement explained in that manual?
- September 27, 2017 at 12:35 pm #47187GoodsteelKeymaster
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CUP measurements always bugged me. I have no frame of reference to that metric. For instance, I know from working in the industry the steel our barrels are made from have a designated yield strength of 93,000 PSI, and annealed 360 brass has a yield strength of 15000 PSI (not that this has any bearing on the PSI our rifles are able to contain, but it is the standard unit strength of materials are measured by).
You would certainly think that a modern reloading book would be offered with real world figures, and yet, even a modern book is lousy with references to CUP pressure figures. When I see that, I always think “gee, thanks a million for taking the time to copy and paste old data for me. Like I couldn’t do that myself without paying you to do it. ie: thanks for nothing”.
This confirms a fear that I have often had when working up close to the top end.
- September 27, 2017 at 4:18 pm #47189
Unfortunately, it’s going to take a long time before the old CUP data is retested with peizo-transducer/strain gauge equipment. It does take time to reload the ammunition and run the tests, especially to SAAMI standards. All the new powders and bullets probably keeps them busy just trying to keep up……….
- September 28, 2017 at 9:34 am #47198Rattlesnake CharlieParticipant
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As Larry said, they are busy with the new stuff. I doubt the older and less popular calibers will ever get updated using the equipment Larry lists. That is also probably why we see some older calibers disappearing from the new manuals. Try finding new data for .32 S&W (not Long) and .38 S&W (not Special).
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