Max load for 158g swc and unique?

[Larry Gibson]

Wiljen

I see where I confused the issue; They use the reference ammuntion to get an "offset" figure to then add to their test loads. That sentence is misleading; should have said they use the reference ammuntion to establish, with the offset, what is the expected psi of the reference ammuntion in their test barrel. That then establishes the base line for load development and a % is, or at least should be, used with additional load development. We are quite in agreement there as I also use a % rather than the set figure to adjust the psi at all levels with load development. However, with the 7.5 gr Unique load of this thread the actual psi's are as recorded. The test barrel I used gives psi's, as noted, within the expectied variation from the reference factory ammuntion using that same lot of ammuntion.

I'm just reiterating what is industry standard according to SAAMI instructions. The above is the minimum they apparently are comfortable with. I, as with you, am not comfortable with just the one offset. I use a minimum of 3 myself using different factory ammunitions as reference ammuntion. SAAMI also is comfortable with one 10 shot string. I am not. I prefer a minimum of 3 ten shot strings to verify accuracy and psi with the highest level of confidence. Most of the ballisticians are comfortable with a minimum of 7 shots in a string for "confidence" that a load is correct. Many use the SAAMI standard of ten shots though. You might have noted in my discussions with DrB that he disagrees and feels a 5 shot group is good enough so even educated opinions vary.

I still prefer 3 five shot test strings or 3 ten shot test strings for psi "confidence" and 3 ten shot test strings at 100 yards or one ten shot string at 100 yards with another ten shot test string at 200 yards to have "confidence" in the accuracy of any load. I have come to prefer those sizes of test strings over the years becuase I have been burned by too many 3 and 5 shot groups, velocity averages and psi measurements that proved to be not correct. Most ballisticians and reloaders find that many in a test to stretch their resources of supplies, $s and time so the lessor numbers are most often used. As mentioned though, for absolute confidence I use 3 ten shot strings for accuracy, velocity and psi measurements but will use 7 - 10 shot test strings for intial work up or for data gathering.

My appologies for the confusion, I have added an additional explanation to my post above.

Larry Gibson

[Nueces]

Larry,

I look forward to anything you post concerning your experiments. It's good stuff, and it's right here on my desk and not months in the future in some gunzine.

You and all others who perform actual investigations, and publish them here, make this forum rich in science and more timely than a scientific journal.

And no one has to say "I'll take it, PM inbound" to get the value.

Mark

[olafhardt]

Back before the rocks got hard and I was studying the flow of gasses we were cautioned to eye with caution any data collected at over 30, yes THIRTY psig. I still do so. We were also cautioned about pressures of still reacting systems. I cannot accepet that piezo, strain or crusher based systems are more than 10%+/- accurate. This means that if your data says 30,000psi, then I take it to be
between 27,000 and 33,000 psi. I do not think of this as conservative. Start slow and work up your best friend is a chronograph, maybe, I shot mine but it still works. Cast boolits ---revolvers nonmagnum 8-900 ftsec, Magnums 1200-1400 ftsec, rifles 2200 ftsec. J things 2600 ftsec. I cant comment on simi autos, high velocity rifles. I shoot for fun.

[Larry Gibson]

Always the best advise is to work up a load. Too many just jump to the top end, have problems and wonder why. Yes "psi" is a "guess" but the methods you cannot accept have been accepted for a long time. As you've said; 'they're the best we have". Also when a psi is posted, as with velocities also, the figure is an average of the test string. There will be some shots of higher psi and some with a lower psi. How much depends on the ES of the load. SAAMI has standards also of how much ES is allowed. I do not post psi's that exceed those unless used as an example and such is specified. Another thing to remember is that each barrel/firearm is different. What is 27,000 psi in my test barrel probably will have a different psi in your barrel.

Another perplexing problem is that we have a physical standards that establish what 1" is, what 1 yard is, what a pint is, etc. However, where is there locked away in a secure place 1 psi to use as the standard? Thus we use the reference ammuntion. Probably not the best but it's the best we've got........

Larry Gibson

[garym1a2]

You did not list the gun you are using. Some I would not even use 6.0 of Unique, yet my Rossi 1892 and the blackhawks can handle a stout charge. Since I assume the reason you want more powder is to get higher velocity than a powder change maybe needed. Slower powders for a longer barrel.

I've been shooting 6.5g under a 158g missouri boolit, the 357 mag 18bh ones. They feel a little on the soft side to me. Is it safe to bump up the charge from 6.5 maybe to 7.5 without risking overpressure? I know some older manuals list a max charge as high as 8 grains while some newer ones only go up to around 6.8 for cast boolits. However the same manual may lists over 8 grains for a jacketed bullet. I like the way 7.5 grains feels with my xtps. Just curious what some opinions are.

[wiljen]

Which strain gauge setup are you using Larry. Got me interested in that I don't think too many of us have them.

[Larry Gibson]

Which strain gauge setup are you using Larry. Got me interested in that I don't think too many of us have them.

Oehler M43 PBL. It uses a VISHAY CEA-06-250UW-350 strain gauge. The test applicable to this thread was conducted with a Contender .357 barrel with the gauge permanantly affixed to the barrel centered over the combustion area of the chamber.

Larry Gibson

[wiljen]

Same outfit I have Larry. I saw a couple others being marketed now and was hoping perhaps you had one of those for comparison's sake. Maybe some other member has one of the newer setups as I'm interested in feature comparison.

[olafhardt]

There are infact primary pressure standards that are traceable back to the bureau of standards, however, I know of none for high prezsures or for systems not in steady state. I talked this over with my son, a professional in a testing lab and has many years exberience. We both think that the amount of confidence people have in these methods is overblown. If I add cyanide to dog food standard dog food tests will read it as protien.. If you want to tell me you shot X grains of Unique behind a 158 boolit and it worked good, bad, whatever out of your gun, OK, I'lltake that. If you want to tell me that it's a good load because so many groups of so many shots gave an average pressure of so much with a standard deviation of so much I hope it does not lead the bore as it goes in one ear and out the other. When I think about it a lot of us shoot for numbers which is OK. But start low and work up. The Chinese killed a lot of our dogs when they added melamine to dog food and our tests read it as protien, even though it was the best test we had. Trusting numbers because they look good can get you in trouble or a dead dog.

[wiljen]

I don't think either Larry or I would put 100% faith in numbers without checking other signs or pressure and behaviors of the rounds we shoot. I think you misconstrue the idea that combined, a chronograph, strain gauge, and common sense give you infinitely more data than the approach of "Its always worked so far" which is what you seem to be advocating. The idea that past experience proves a round safe is flawed especially with all the variables involved in taking anyone else's load data.

I don't rely 100% on my tools to tell me whats good, but I do use them to tell me when I would be making a mistake by blindly assuming things to be good.

[olafhardt]

I hope I have not given the impression that I hold anyone in ridicule, I don't. I think this forum contains some excellent research and commintary as does the entire site. However, in matters ballistic I tend to trust empiricle data over instrumental. Anybody can blow up a gun, it takes a genius to find the minimum blow up load.

[Sailormilan2]

Just as an interesting factoid, the 45th Lyman reloading manual lists a max load of 8.0 gr of Unique for the 158 gr SWCGC, with a MV of 1250 fps. And, as Larry pointed out, the newer versions(47th and 49th Editions) don't list Unique. They do list a max load of Herco as 7.5 gr giving a pressure of 41K CUP.
What is scary is that the 45th Edition lists a max load of Herco as being 11.6 gr, giving a MV of 1388 fps. This is listed as a "Factory Duplication" load. I wonder what the pressure was for that load? Gives me more respect for the Model 27 it was fired from.

[Char-Gar]

I will stay far way from the science/pressure stuff, because I know nothing about it. That said, I will ask the OP why do you want or need max pressure loads?

I have been loading for various 357 Mag revolvers for 50 years or so and can't remember any time I needed max pressure/velocity load. I have never hunted deer with that caliber, so my needs might change if I did.

These days, I load a solid base full wadcutter or either 10/2400, 7.5/AA5 or 5/Bullseye. These loads are very accurate as far as I can hit anything with a handgun. Have about the same velocity 1,000 to 1,100 fps depending on firearm and barrel length. The pressure and velocity are above 38 Special loads and make very effective field and defense loads, although they will likely give through and through penetration in a human body. They are also easy on handguns and are easy to control and shoot with accuracy.

I see no need to shoot red line loads in any firearm unless there is a real need. "Just because you can", is not a real need. This is a major reason we handload, to have options other than what factory ammo gives us.

[derek45]

unique is great for medium level loads

if you want “warmer” buy some 2400 or H110/win296

It makes no sense to try to hot rod unique in 357
.