Thanks for the reminder Larry. I have a pet load for my 7mm STW that is amazingly accurate, but based on early data. I need to rethink my load.
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"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."
Brass extrudes in all directions so that tells me there had to be some indication of flow into the ejector hole, maybe minute but there. I guess if a load has been shot before and deemed safe it could be overlooked, but usually makes a bright mark as the bolt is rotated to eject. Maybe we could get a picture of the case heads of brass with loose primer pockets? Some of the older manuals were notorious for "hot loads" Hodgdon #26 shows 56.0 gr H4350 as max for 180 gr bullet but no manufacture is shown.
Last edited by swheeler; 10-02-2017 at 11:20 AM.
Charter Member #148
The rest of the lesson is that because there is NO reliable method to determine pressure other than a transducer, published maximums using copper crusher are suspect and should be avoided unless you have other evidence to support your data. Other evidence would be chronograph data (at the least). Inspecting primers and case head expansion is bogus for most reloaders because they don't start from a known point or know how to keep proper records.
Last edited by oldblinddog; 09-30-2017 at 11:55 AM.
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Well, I am one of those Greybacks and I can remember articles in Handloader/Rifle debunking these methods. The point is/was that by the time you start to see any signs you are well beyond max pressures. Besides, there is no improvement in trajectory that you can't negate just by how you hold the rifle in the field. The pursuit of "max" velocity is a futile endeavor. Look at the loads used by our snipers shooting the .308/7.62x51. Best accuracy and knowing your load is better. But then, that's just my opinion.
USMC 6638
a m e r i c a n p r a v d a
Be a Patriot . . . expose their lies!
“In a time of deceit, telling the truth is a revolutionary act.” G. Orwell
Then Speer is crazy too. They list 58 gr with their 180 gr bullets.
Excellent work Larry, a very interesting and informative read! At times I have come across data that made me wonder how a company could possibly recommend it to the shooting public. Case in point, a load from Speer #8 for .38 special listing a rather healthy dose of #2400 powder, tested in a "K" frame. I worked up that load to a max load as listed, As I increased the charge weight accuracy improved until all I had was a jagged little hole at 50'. It was an interesting experiment and I'm sure pressure was over +P, but in the end I decided it was too much for my M-67 and discontinued use of it. To be fair, Speer noted that regular use would "loosen" the gun.
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"Excellent work Larry, a very interesting and informative read."
As I said in my first post on this subject pasted below.
No data from anyone should be taken as 100 percent reliable. From a Lab, individual or gunshop.
Can anyone prove that Hodgdons didn't get the results they listed with that test barrel, lot of components etc. at that time?
Maybe they did but maybe they didn't. Who knows.
Here is my first post.
"What I have taken out of all this is that NO loading data from ANY SOURCE can be counted on 100 PERCENT of the time.
This is something most veteran reloaders will probably know but are subject to forget at times.
This episode should be enough to reinforce the idea that relying 100 percent on any source of load data is bordering on the irresponsible even from a person that one perceives to know what they are talking about."
Can someone explain...in a short paragraph.... how the Oehler M43 detects actual chamber pressure?
Now I am by no means educated on this subject, but I did find this....
"I have worked with RSI on this unit's development and personally use it--and it is VERY neat. Unlike the old (and no longer available) Oehler M43 Ballistics Lab pressure unit which attempts to equate the pressures obtained in your gun to what would be obtained by firing that load in a SAAMI specification pressure barrel, PressureTrace gives the actual psi readings generated in your gun--a much more useful measurement. The Oehler readings are higher in most cases than the actual pressures generated in the gun. Oehler apparently included this quirk because their idea was to sell the units to commercial users who could then develop loading data traceable to SAAMI data for liability reasons".
Is it possible that the Oehler Data is off? And there has been recent reports of Winchester brass with loose primer pockets from the factory. On the other hand, the excess velocity is suspicious. Again, not doubting Larry's findings. I'm not adequately educated enough on measuring chamber pressure to do so. All I can do is ask questions.
Last edited by buckshotshoey; 10-02-2017 at 10:25 AM.
Strain gauge glued over the chamber. Which like anything man operated is subject to error.
And not particularly well calibrated to be honest. A bunch of engineering goes into creating an accurate pressure barrel. A strain gauge on your gun can be calibrated and will provide more data points than a chronograph. It can be a guide in load development, but is still doesn't make your gun a lab grade pressure system.
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Larry Gibson is correct to post his findings on that load in his first post.
While I am cautious of all load data I am a believer in his findings on Hercules and now Alliant 2400 charges.
I use 21 gr 2400 as my upper load in the 44 Magnum.
Ocassionally we need to be reminded of these things.
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |