445 SM Pressures

[LaOtto222]

I keep hearing that it unsafe to shoot a 445 Super Magnum on a SB1 frame. Thinking about this I really can not figure out why that is true and not just a gut feeling. Follow my thinking and then give me a real world reason for not doing it. As far as I know, there is no official SAAMI pressure data for the 445 Super Magnum. The case head for the 445 SM is the same diameter as the 44 Magnum. Assume the 445 SM is loaded to the same pressure as the 44 Magnum. If that is true, why would a 44 Magnum be safe on a SB1 frame but a 445 SM would not be safe. I realize that if you load a 445 SM to the maximum you can, it will be too much for a SB1 frame, but the same could be said of the 44 Magnum. If you load the 44 Magnum, past it's designed pressure (36K psi) then it would be dangerous on an SB1 frame too. Since the 445 SM has a higher case capacity, when you load it to the same pressures as the 44 Mag, it should be just as safe and get more velocity. I have been told many times that the 45-70 shoots harder than a 444 Marlin because of case capacity. The only reason I can think of, is someone would load the 445 SM to pressures above the 44 Magnum. I am not sure what pressure level they would load to, but the same thing could be said of the 44 Magnum, load it too high (say 16 grains of Unique) and it becomes a bomb. I do not have software to predict what would be a velocity that would be safe. Is the velocity prediction too low to be worth while? Is there any real reason to not shoot a 445 SM on an SB1 frame? Tell me what I am thinking that is wrong and why, please.

Good Shooting and Good Luck

[quickdtoo]

To put it simply, the old 44mag SAAMI MAP was 40kcup(not kpsi), published data for the 445SM is out there to 43.3kcup and above I suspect, that's why I don't recommend full pressure 445 loads on a cast iron frame.

Tim

[LaOtto222]

I looked for pressure data on the 445 SM, but could not find any. Where did you find it? It was not listed in the SAAMI site. So I was thinking that pressure levels are arbitrary for the 445 SM. Of course when there is really no guide lines, people have a tendency to push the limit. 36K psi is what I found for the 44 Mag as an industry standard. I think that psi is a more reliable way of comparing pressures. CUP is not really the best way of comparing one case to another, especially with different case capacities.

Has anyone cracked an SB1 frame with a 43.3K CUP level load, that you know of? Do you know of anyone that has put a 445 SM on an SB1 frame and what was their experience? Do we really know what the published load data pressure is? Have you ever run the data through your software to see what pressure we would expect from published data? 

I am just doing a brain exercise. I have a 44 Mag, but do not have a desire to ream it and if I do, I have an SB2 frame it will fit on.

Good Luck and Good Shooting

[YRUpunting?]

Before I had H&R put a 44mag barrel on my SB1 I asked about using +P ammo.  I was told absolutely not.  Obviously they have a legal team worried about liability but it was a quick and emphatic no.

[quickdtoo]

I looked for pressure data on the 445 SM, but could not find any. Where did you find it? It was not listed in the SAAMI site. So I was thinking that pressure levels are arbitrary for the 445 SM. Of course when there is really no guide lines, people have a tendency to push the limit. 36K psi is what I found for the 44 Mag as an industry standard. I think that psi is a more reliable way of comparing pressures. CUP is not really the best way of comparing one case to another, especially with different case capacities.

Has anyone cracked an SB1 frame with a 43.3K CUP level load, that you know of? Do you know of anyone that has put a 445 SM on an SB1 frame and what was their experience? Do we really know what the published load data pressure is? Have you ever run the data through your software to see what pressure we would expect from published data? 

I am just doing a brain exercise. I have a 44 Mag, but do not have a desire to ream it and if I do, I have an SB2 frame it will fit on.

Good Luck and Good Shooting

There is no SAAMI MAP for the 445SM, I posted the only published 445 SM data source with pressures I've seen, it's in CUP, that's why I used the old SAAMI 44mag specification which was in CUP also for comparison so it wasn't a worthless apples(PSI) and oranges(CUP) comparison, see the attachment in my first reply. Hornady has data, but no pressure listed.

Tim

[petemi]

All my center fire Handis are on SB2 frames.  For the price of a  box or two of ammo added to the cost of a SB1, you don't even have to think about stuff like this.  I've got an ad in right now for SB1 frames.  I've got two shotguns sitting unnecessarily on SB2s that could be put to better use.

Pete

[LaOtto222]

Before I had H&R put a 44mag barrel on my SB1 I asked about using  P ammo.  I was told absolutely not.  Obviously they have a legal team worried about liability but it was a quick and emphatic no.

This does not surprise me any. H&R does not want you to use 5.56 NATO ammo in a 223 either, even on an SB 2 frame. You can load up any ammo to unsafe levels, so when you say +P with a 44 Magnum, I would recoil at that also. What is  +P for a 44 Magnum? 40K psi, 44K psi?

I would think that if a 445 SM @ 43.3K CUP is too much pressure for a SB 1/Cast Iron frame, then a 44 Magnum at just 8% less pressure, would not be all that safe either. Yet there are thousands of 44 Mags setting on SB 1/ cast iron frames, none with a problem. I say none with a problem, because if there were, they would not be putting 44 Magnum barrels on those frames.

I am still curious how the 43.3K CUP was determined and who did it. Plus a comparison of one cartridge's CUP does not correlate directly to another cartridge CUP pressure, especially if the case capacity is different.

I fully understand why anyone would say not to go into uncharted waters, because some fool could load up a case to very high pressures and then blow up a gun or worse. They would come back and say, you said it was OK to load cartridge X with my SB 1 frame. But that could happen with any frame with any case if someone uses unsafe loading practices or pushes the limit all the time.

Good Luck and Good Shooting

[BAGTIC]

Q uick Load gives 40,611 psi for 445 SM. As the H&R SB2 is factory chambered for the much larger 500 S&W Magnum at 61,931 psi there should not be any question about the 445.  Even the 40,611 psi figure works out about the same breech thrust as a common 12 gauge shotshell in the SB1 frame. If the shotshell type firing pin doesn't cause a problem it is unlikely that there would be any.
Use conservative loading practices, start low, and increase accordingly. 

[quickdtoo]

Q uick Load gives 40,611 psi for 445 SM.

Look again, QL doesn't specify the measurement method, lists "unknown", not SAAMI, CIP or Wildcat.  At least the Accurate data states a known value in CUP which is higher than 40611psi.

Tim 

[nanuk-O-dah-Nort]

all the info I can find points to a 41K chamber pressure, giving a 6.7K breech thrust

12ga 3" at 5.9k
12ga 3.5" at 7.2k
303Brit at 8k
All SAAMI

note:  CIP 44RemMag is 41k PSI, same as the 445SuperMag.

As Quick says, stay within reasonable loads and with the extra room, and slower powders, you'll get the increase in velocity, or same velocity with heavier bullets.
think 30-06 over the 308!

[BAGTIC]

Q uick Load gives 40,611 psi for 445 SM.

Look again, QL doesn't specify the measurement method, lists "unknown", not SAAMI, CIP or Wildcat.  At least the Accurate data states a known value in CUP which is higher than 40611psi.

Tim
True but "PSI" is an indication that it was not 'CUP'. It also tends to indicate that it was the maximum pressure during the powder burn. CUP indicates the maximum pressure at the crusher gauge port and can be very dependent on the location of the port just as the location of a gas piston port on an autoloading gun affects the port pressure.
As there is not any way to convert CUP and PSI ratings and there are not any official standards anyway it is a matter of working up loads gradually. SAAMI standards provide a margin of error of about 30% via proof loads and it is unlikely that any manufacturer would design a gun to fail at proof load levels.
The reason H&R and other companies will not endorse the conversion is obviously legal. It is the reason almost all gun manufacturers repudiate the use of any handloads or ammo loaded by SAAMI non-conformant companies. They also will not sell unchambered barrels, even unmarked ones, because they have no control over what they turn into. It is plausible deniability.