A couple of pressure questions

[Classicvette63]

Why are some powders max loading well under peak pressure? Example, in Hogdons manual, the max load for a 158gr hp in a 357 magnum with either H4227 or H110 generates over 40,000 c.u.p. Lilgun is kept at a max for that load of 25,800c.u.p. Why is that? If the gun can take 40,000cup of H110, why can't it take 40,000cup of Lilgun?

Another question I have is, I see how the pressures of new cartridges are way above older, albeit modern rounds. How far can they go in pressure? If you had the steel or alloy to hold 100,000 or more, would it be worth it? Is there some point of diminishing returns?

[skeet]

Not having the manuals available right now I don't know the answer to the first question... The second is a bit easier. The pressures for the newer cartridges and powders are now listed in PSI for the most part whereas the older data is listed in CUP copper units of pressure. There can be(and usually is) a great deal of difference in the two. Also the newer cartridges like the "NEW" short mags etc are loaded to higher pressures because the companies know that most of the rifles that use them are new modern actions made of new modern stronger steel. The darn companies are loading the old favorites like the 30-06 to lower pressures now days because there are a lot of tired older rifles and actions. The 06 is now over a hundred yrs old:eek: I wouldn't shoot an old 1895 Winchester in 30-06 with new ammo....but some surely would! The companies are definitely ruled by lawyers now days

[Ol` Joe]

Some loads use powders that fill the case before enough powder is used to produce top pressures. There are other loads that may not be uniform enough in pressure highs and lows to allow the use of loads that average peak SAAMI pressure. Pressure isn`t the same in every load and there can be very large swings between high and low in some cases. The listed figures are averages of the labs findings and there may have been a peak recorded that went 5K psi higher that you don`t see in the data.

For your question on building a firearm to take greater pressure then presently done , remember the whole is only as strong as the weakest link. The case is much weaker then the steel action now used. Stronger guns may be possible but if you experiance case failure it won`t help.

[PJgunner]

Originally posted by Classicvette63
Why are some powders max loading well under peak pressure? Example, in Hogdons manual, the max load for a 158gr hp in a 357 magnum with either H4227 or H110 generates over 40,000 c.u.p. Lilgun is kept at a max for that load of 25,800c.u.p. Why is that? If the gun can take 40,000cup of H110, why can't it take 40,000cup of Lilgun?

I don't know what Lilgun looks like but either it takes up too much room in the case or it's burning rate (tolerance level) is such that pressures get squirrelly as they grow higher. Each powder has a level where if the pressure is too low or too high will react differently. If could be that if pressure is much more than that 25.8KCUP, then pressure rapidly get out of control. That's my best guess.

Another question I have is, I see how the pressures of new cartridges are way above older, albeit modern rounds. How far can they go in pressure? If you had the steel or alloy to hold 100,000 or more, would it be worth it? Is there some point of diminishing returns?

Ok, first off, it is not the strength of the steel in a rifle that's at issure, but the cartridge case. certain cartridges, due to the fact that they are chambered in rifles of questionable strength are not loaded to their full potential. Several good examples are the 7x57 Mauser, 30-06 and yes, ever the recently legitimized .35 Whelen just to name a few.
To continue the example, take the 7x57. originally chambered in 1893 and 1895 Mausers to a specified pressure level of 45KPSI. (Actully should be CUP, but they called the data PSI back then.) This affected the pressure level of the .257 Robt. as quite a few of those old rifles were rebarreled to the Robt. Seems like Spain rebarreled a bunch to the 7.62 NATO round and they were imported into the U.S. as .308 Win. and were declared perfectly safe for .308 Win. factory ammo, a 50KCUP round. :eek: Factory 7x57 with 140 gr. bullets are normally loaded to an "advertised" 2600 FPS. My handloads for the cartridge run 2800 FPS with a 140 gr. bullet in a modern Winchester Model 70 Featherweight.
So yes, if you have a modern rifle like the Winchester m70, Remington M700 or Ruger M77 as examples, you certainly can improve ballistics by careful handloading.
As an example, when I worked up that 140 gr. 7x57 load, I did it in the middle of an Arizona summer. Outside air temperature was arounf 105 degrees that day, as I recall. The final load tested was 2880 FPS, but I felt I was nearing a pressure threshold and reduced the load back to 2800 FPS. During a normal hunting day here, the temperature in the morning can be at or slightly below freezing and by late afternoon right at 80 degrees. My load worked up at 100 plus degrees should be perfectly safe during hunting season.
I use a dial caliper, micrometer and a chronograph when working up these loads.
Look at it this way. A .300 Win. mag., for example, is loaded to about 60KPSI and a 30-06 is loaded to about 50KPSI, both levels give or take a bit. Say you have a Ruger 77, Remington 700 or Winchester m70 chambered to the 06. There is no reason why you can't load the 06 to the same pressure level as the .300. They don't use weaker steel in the 06. The big hang up is getting usable data at that higher pressure level, and at that point, you're on your own. Once you go past any printed manual data, you are in, for all practical purposes, in uncharted terrirtory. I'd almost be willing to bet though, that the guys at Sierra, Hornady and Hodgden do have that 60K data for their own use. They just can't pass it on due to the lawyers.
Do I advise anybody to try what I've just described? Do I even suggest anybody do the above. Not only no, but hell no! As I said, that's uncharted terrirtory and if you try it, you're on your own.
Paul B.

[Rocky Raab]

The first one is easier. Different powders are -- different. Lil Gun just happens to produce high amounts of gas volume but at lower pressure, so you can get what almost amounts to a free lunch: good velocity at low pressures. It doesn't react that way in every cartridge, but it does in some.

Older guns weren't made with today's alloys or today's methods of heat treating. They really don't make them like they used to - they make them better!

Loading data for older cartridges (and their older rifles) like the .30-06 occasionally are reduced reflecting the fact that the rifles themselves are getting more and more used, worn and weaker. A cartridge invented yesterday doesn't have the problem of century-old rifles that can chamber it.

[Riposte1]

To add to what Rocky wrote (and fully in agreement) there seems to be on rare occasions just such things but they might happen only with the exact example test gun in the lab.

I found such a load in the older lyman manual (46 perhaps or maybe a cast bullet manual) which drove a 158 gr SWC over 1400 from a 4" .357 whith H110. That load did in fact work in my S&W 4" 19 (actually I got 1450 fps!!!) but when I tried it in a 4 3/4" Ruger Flattop the cases stuck. It also showed excess pressure in other guns.

One simply has to go careful. If it sounds too good to be true, it probably is. Not to say there are not some "niche" loads.

Riposte