44 Mag LSWC Seating Depth Impact on Pressure

[BigBoreReloader]

I’ve been reloading for a while now, but came to a seating depth/COAL crossroads. I am loading a 240gr LSWC over 22grs of IMR4227 (Hodgdon’s published 44 Magnum load data). The COAL they list is 1.62”, which chambers fine in my revolver, but seems to have difficulty in my lever gun. I believe SAAMI specs have a max COAL of 1.61 so I suspected that is the issue. I was able to reduce the COAL to just under the SAAMI max to 1.607, and now they chamber fine.

The question is, do I risk a spike in pressure? I doubt it, given such a small reduction of -0.013” but I have not needed to seat deeper on any of my various pistol calibers before, and know seating too deeply could have a catastrophic outcome/pressure spikes. How much is too much?

[gwpercle]

As long as your load isn't a Maximum Load ... a 0.013" increase in seating depth on a mid-rance or light load would be just fine . If your load is a heavy / maximum type load then drop back 10% and work back up slowly looking for pressure signs .
But honestly ... 0.013" isn't a very large amount ... but better safe than you know ... Sorry
Gary

[BigBoreReloader]

As long as your load isn't a Maximum Load ... a 0.013" increase in seating depth on a mid-rance or light load would be just fine . If your load is a heavy / maximum type load then drop back 10% and work back up slowly looking for pressure signs .
But honestly ... 0.013" isn't a very large amount ... but better safe than you know ... Sorry
Gary

Thank you! That was my first thought, but, as luck would have it, Hodgdon does not list a starting load, just shows 22grs as max, so I have been hesitant to adjust this in either direction. I have not had to mess with seating depth much for pistol loads before... at what point would you consider it to be a "large amount"?

[fredj338]

Even at max load, seating 0.013" is meaningless, especially with slow powders. Put 0.013" on your calipers, means nothing. Your case volume variation would have a greater affect. Seating deeper has a greater affect with small volume, fast powder applications. Even then, if not a max load, 0.013" is insignificant.

[Larry Gibson]

While .013" difference in seating depth may seem not it "isn't a very large amount" it can increase pressure 4 - 6,000 psi in the 44 Magnum case. However, with 4227 powder under a 240 gr LSWC the psi will be very low, well below the SAAMI MAP.

FYI; in pressure testing 23.5 gr of H4227 under a 254 gr RCBS 44-250-KT with various primers the highest average psi measured was only 30,800 psi. The SAAMI MAP for the 44 magnum is 36,000 psi.

[BigBoreReloader]

While .013" difference in seating depth may seem not it "isn't a very large amount" it can increase pressure 4 - 6,000 psi in the 44 Magnum case. However, with 4227 powder under a 240 gr LSWC the psi will be very low, well below the SAAMI MAP.

FYI; in pressure testing 23.5 gr of H4227 under a 254 gr RCBS 44-250-KT with various primers the highest average psi measured was only 30,800 psi. The SAAMI MAP for the 44 magnum is 36,000 psi.

Thank you for that... I hesitated primarily because 1) this is already a compressed load and 2) Hodgdon only listed a max load of 22gr. They show est pressure of 33,300 CUP (which I think is equiv of ~33k PSI?), so I was concerned compressing further would push that above

[Larry Gibson]

Thank you for that... ....... They show est pressure of 33,300 CUP (which I think is equiv of ~33k PSI?), so I was concerned compressing further would push that above

You're welcome.

In a vary narrow band there is a similarity between CUP and PSI's However there is no direct correlation or conversion factor. The SAMMI MAP for the 44 magnum cartridge is, as I mentioned, 36,000 psi. Conversely the SAAMI CUP MAP is 40,000. Assuming them both to be the same "MAP" we see there is a difference.