Vicarious 44-40 Pressure Testing
Savvy Jack has done considerable pressure testing of the 44-40 cartridge in a special fixture. His work mainly revolved around testing Black Powder loads. While commendable Savvy’s tests did not answer several questions on loads Outpost75 proffered. Winter had also set which severely restricted Savvy’s ability to test loads. Even though I test pressures via the Oehler M43 PBL (Savvy Jack uses a Pressure Trace System) I do not have a 44-40 test barrel. However, I do have a 44 Magnum test barrel.
Based on Savvy Jack and Outpost75s exchange I wondered if there was a way to correlate pressures obtained in the 44 magnum cartridges to the 44-40 cartridge(?). I had measured the case capacity of both cartridges using RL7 powder and found the case capacity of the cartridges (both were W-W cases) was very close.
Attachment 266142
I had read in the past that given equal loads the pressures in the 44-40 would be about 95% of those in the 44 Magnum. Thus I pondered to Outpost75 the following hypothesis;
“ …I’ve measured the capacities or W-W 44-40 and W-W 44 magnum cases every way from Sunday and found they have essentially the same capacity. So, if I pressure test loads in 44 magnum cases in the 44 Magnum test barrel might they not give comparable pressures or at least a useful correlation figure? “ It was decided through further discussion I would pressure test some of Outpost’s 44-40 loads and my own 44-40 loads in 44 Magnum cases. Then selected known pressure loads could be chronographed in the same OM Vaquero revolver with 7 ˝” barrel using the original 44-40 cylinder and the 44 Magnum cylinder from my FTBH Ruger 44 magnum. The Ruger FTBH 44 Magnum cylinder fits, indexes and has the same barrel/cylinder gap as the original 44-40 cylinder.
Attachment 266143Attachment 266144
Thus, we theorized if the same load in the different cartridges in the same revolver gave essentially the same velocity [there is always be some variation to be expected though] then we could assume the pressure to be the same. If not, would the differences be consistent enough that we could deduce a correlation factor such as the “95%” figure previously mentioned?
With that in mind I received from Outpost75 test samples of two of his bullets to test; the 43-206H and the 43-230G, both from Accurate moulds. I supplied two bullets also; the Lee 429-200-RF and the Lee TL430-240-SWC which I most often use in the 44-40 cartridge. All the bullets were sized .430 and lubed with BAC. Those four cast bullets would cover the most used weight ranges used in the 44-40 cartridge.
Attachment 266145
The testing would be conducted in two phases; phase one would be pressure testing the selected loads in the Contender 44 Magnum test barrel. Pressure data would be measured and processed via the Oehler M43 PBL. Phase two would be chronographing in the Ruger OM Vaquero via an Oehler M35P chronograph with the start screen at 10 yards from the muzzle in both 44-40 cases and 44 Magnum cases selected from the pressure tested loads using the two different cylinders. Some of the 44-40 loads would also be chronographed in the Chiappa M92 carbine just for the information.
All cases used in both pressure testing in the Contender test barrel, the Ruger OM Vaquero revolver and the Chiappi M92 44-40 carbine in cartridges of 44 SPL, 44-40 and 44 Magnum were W-W cases. They were sized and loaded in RCBS dies for both cartridges. WLP primers were used throughout. Each bullet was seated to the crimp groove and a light crimp applied just enough to prevent bullet set back in a tube magazine. The TL SWC was seated to and crimped in the front lube groove. No set back or bullet jump was encounter during testing in the revolver or M92 lever action.
The initial pressure testing of the selected loads would be done in my 44 Magnum Contender barrel;
Attachment 266146
The line connected to the strain gauge (shown in the photo) is connected to the Oehler M43 PBL. The strain gauge is permanently affixed to the barrel located at the SAAMI recommended point of transducer location. Previous testing with “reference” ammunition [factory loads of known psi measurement] shows this gives very comparable psi measurement to piezo-transducer measurements. However, there is one thing we must understand when taking psi measurement with a strain gauge. It takes 7,000 + psi to fully obturate most brass cartridge cases to fully seal the chamber and to put stress on the chamber walls [this is why many low pressure loads have “sooty” cases because they do not fully obturate against the chamber walls]. Then, for the strain gauge to measure any “stress” on the barrel steel, it requires several thousand more psi to induce enough stress. Thus, the lowest psi I measured of any shot during the testing was 11,300 psi but since it was with the 44 SPL cartridge I decided to use the lowest measurement obtained in 44 Magnum cases during this test.
The lowest psi measurement during this test with the W-W 44 magnum cases was 13,300 psi. Ergo, I conclude that if any shot fired in W-W 44 Magnum cases does not register a psi measurement then the psi is less than 13,300 psi.
As an example; one of the loads Outpost asked to be tested was his favorite 44-40 load of the 43-230G bullet over 6.0 gr of Bullseye. He pondered if there was any real difference between older Hercules Bullseye and newer Alliant Bullseye. As I had been given an older square tin of Hercules Bullseye which was still sealed, I thought I might be able to answer that question. There was no date on the older tin of powder but it was obviously old…perhaps someone knows when Hercules stopped using those tins?
Attachment 266147
I opened the tin of Bullseye and inspected the powder and found no sign of deterioration, so I loaded a 10 shot string of 6.0 gr of the Hercules Bullseye along with a like test string but with 6.0 gr of current Alliant Bullseye. Both under the 43-230G cast bullet.
Neither test string registered any psi measurement thus we can conclude the psi was less than 13,300. I did track the velocity of each test shot. The average for the Hercules Bullseye load was 965 fps with an ES of 27 fps. The average of the Alliant Bullseye load was 961 fps with an ES of 33 fps. Essentially, we can therefore conclude, the Hercules and Alliant Bullseye powders are basically identical in burn rate per gr of powder. This and other testing demonstrate little change in burn rate, if any at all, between older Hercules and current Alliant powders of the same kind.
Phase one testing results;
All test strings throughout testing (pressure and velocity) were 10 shot strings. The data from loads that were pressure tested in the Contender 44 magnum test barrel;
44 SPL; Outpost75 requested a pressure test of his 44 SPL load with the 43-206H (213 gr) loaded over 6.0 gr Bullseye. It proved to be an excellent load in terms of its internal ballistics and on target performance. Accuracy was excellent, velocity was very uniform with an SD of 11 fps and an ES or 35 fps. The average psi was 14,000 with an SD of 400 psi and an ES of 1,200 psi…..an excellent load.
Data from 44-40 duplication loads tested in 44 Magnum cases in the 44 Magnum Contender test barrel:
429-200-RF (200 gr) with 6.0 gr Bullseye; no pressure measurement thus psi less than 13,300.
429-200-RF with 7.5 gr Bullseye; the average psi measurement was 17,800.
43-206H (213 gr) with 6.0 gr Bullseye; no measurement thus psi less than 13,300.
TL430-240-SWC (242 gr) with 6.0 gr 700X (my Vaquero and M92 load); no psi measurement thus psi less than 13,300.
429-200-RF with 25 gr RL7; only one shot gave a psi measurement of 14,800. The other 9 shots were less than 13,300 psi.
43-206H with 25 gr RL7; the average psi measurement was 17,300.
43-230H (233 gr) with 25 gr RL7; the average psi measurement was 20,300.
TL430-240-SWC with 25 gr RL&; the average psi measurement was 24,400.
Phase two test results:
Six loads were selected to be loaded in both 44-40 and 44 Magnum cases for chronographing via the Oehler M35P using the Ruger OM Vaquero 7 ˝” barrel revolver with both its original 44-40 cylinder and with the FTBH 44 magnum cylinder. I’ll also list the velocities chronographed with selected loads in the 44-40 Chiappa M92 carbine with 20” barrel.
Load………………………44-40 fps…44 Mag fps…M92 fps
429-200-RF/6.0 gr BE……..947……… 1016………..1188
43-206H/6.0 gr BE………...903…………970………..1121
43-230G/6.0 gr BE………...881…………937
TL430-240-SWC/6.0 gr 700X..858……...937………..1061
429-200-RF/25 gr RL7……1053………..1130…… ..1428
43-230G/25 gr RL7………..1071……….1163
TL430-240-SWC/25 gr RL7..1157…........1204……….1488
All loads in 44-40 cases gave less fps than the same load in 44 magnum cases in the same revolver. The average difference is the 44-40 produced, on average, 93.4% as much velocity in the 44-40 cases as the same load did in the 44 Magnum cases. That does seem to suggest that what I had read years back about the 44-40 producing 95% +/- as much psi as with the same load in a 44 Magnum case is correct. So, is there a correlation we can use to determine safe pressure 44-40 loads with pressure testing being done in the 44 Magnum pressure test barrel? It appears so. Since all was equal in the revolver except the chambering and since velocity is directly related to pressure [all other equal as was in this test] I think we can safely conclude a load that produces so much pressure in the 44 Magnum will only produce 93 – 95% of that pressure in the 44-40 cartridge.
Note; nothing in this test is meant to imply any 44 magnum level psi is safe in any 44-40 chambered firearm. This test is only inferring we can find safe 44-40 level psi’s by testing 44-40 level loads in the 44 magnum test barrel.
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Originally Posted by Larry Gibson
