454 Casull/ 44 Magnum Pressure Question

[Palladan44]

**This is strictly for curiosity purposes only, I'm not loading any loads over Book maximums nor should anybody**

I'm interested in the fact that 44 Magnum is rated up to SAAMI 35,000psi.
I just learned today that 454 Casull is SAAMI'd for 65,000 psi. WOW, right!

I'm curious to the fact that visually, and dimensionally, the 454 and 44 Magnum have more similarities than differences.
I'd say that the 357 Magnum (also pressure rated about 35,000psi) is further away dimensionally from the 44 Magnum, than the 44 Magnum is from the 454 Casull.....

I'm also fairly certain that similar (or the same) powders give top performance in these respective cartridges....these powders being basically "a case load" of powders like WW296, H-110, 300MP, Lil- Gun.

I also notice that for the most part the same firearms are chambered in both of these rounds from Taurus, Ruger, and other firearm makers.....

So what gives here? Why almost double the pressure in 454 Casull?

 

[BBarn]

The cases and firearms in 454 Casull are designed for the substantially higher pressure. One big drawback to loading the round at full pressure is case life. Speer cautions that their max loads should use new unfired brass only. It's also likely that some factory rounds are loaded to levels below 65 kpsi.

 

[243winxb]

454

Ruger made a cylinder from Custom 465 stainless, then fired 50 proof rounds from each of six chambers (total 300 rounds) at 92,000 psi

https://www.carpentertechnology.com/blog/most-powerful-revolvers-get-lift-from-aerospace-alloys

 

[Cheesemaker]

The 454 - at least in the Rugers I own - have an unfluted cylinder, giving it more mass.
The pressure for the 454 is on par with the 460 and 500 S&W Mags. There has been some debate that the 460 S&W is not materially superior to the 454. Seeing that they shoot the same projectiles (at least I do) 240 & 300 gr Hornady XTP Mags, at similar pressures there should not be a whole lot of difference. The 460 does have a lot more case capacity though.

The 44 used to be the "big dog" but it does not hold a candle to the power a 454/460/500 can put out. I consider the 454/460 and 500 in the "same league".

 

[Targa]

I load my attention getting .454 Casull rounds with 37.5 grains of H110 under a 240 grain Hornady XTP hollow point. I ran it through my chronograph at an average of 1737 fps out of a 6.5” barrel. This load is still a few thousand psi under the 65,000 that it is rated for but that 37.5 grains is my limit. For the most part I am running 325 grain cast bullets over 25.5 of H110 putting it just south of 40,000 psi. It is still a hammer but is much more enjoyable.

Now the .44mag, I have a plethora of different loads developed for that from 200 grain to 310 grain bullets none of which match the felt recoil from even my “friendlier” 325 grain Casull loads.

 

[Cheesemaker]

Here is Hodgdon's compare of a 44Mag/454Casull/460S&W - all with 240gr (varying bullets)/H110, different barrel lengths, different primers.
The 454 has ~500ft/ps over the 44 at ~1.5 times the pressure, 1" more barrel
The 460 has ~150ft/ps over the 454 at similar pressures AND the 460 has a 1.5" barrel advantage and uses >10gr more powder at max charge.

 

[WrongHanded]

So what gives here? Why almost double the pressure in 454 Casull?

My assumption here is that when SAAMI established the specs for .454 Casull, it was done with materials and technology not available when the .44 Magnum became a commercial product.

1955 vs 1997. At least according to wikipedia, which might be wrong.

 

[Palladan44]

My next question:
Some argue that Small Pistol "Magnum" primers are the exact same primer as Small Rifle Primers....they are just boxed and labeled differently? (**Don't take this as fact internet readers, this is a question I'm asking here**)

454 Casull uses Small Rifle Primers.
357 Magnum uses, in many cases, Small Pistol "Magnum" Primers.
357 Magnum starts to "flatten" primers around its maximum limit of 35,000-40,000 psi.
I'm wondering how the arguably exact same primer is able to stand up to nearly 65,000 psi in 454 Casull and not have extreme problems with flattening, or blowing out?
It's possible it has to do with the larger case volume, and slower burning powder building up pressure more slowly, allowing obturation of the primer, before primer setback?

 

[Barr]

Rifle primers have thicker cups to resist piercing due to higher pressure. Easy way to prove is to “section” a dead or inter primer and compare cross-section(s).

 

[Cheesemaker]

See this recent thread: https://www.thehighroad.org/index.php?threads/small-pistol-primers-small-rifle-primers.897609/

 

[Barr]

Remember MAP stands for maximum average pressure, each powder and cartridge generates a different pressure curve.

50+ years ago ballisticians, engineers, and scientists used a copper crush cylinder to make comparative analysis of peak pressure in universal receivers in laboratories. It used a known copper cylinder properties with a piston to measure the cylinder deformation.

It has only been in the last few decades that piezo-electric sensors and wheatstone bridge strain gages have allowed us to develop time-pressure curves. A piezo-electric crystal directly varies electric signal strength with regards to growth (pressure).