Got GRT Working Pretty Well
I discovered it is the same in the Advanced Interface. It is just that as the way the load window comes up after installing the program, the bottom of the bullet window is cut off by the top of the charge window. When I manually pulled the top of the charge window down, the full bullet window appeared and remains that way after exiting and restarting.
That window discovery leads to my second discovery, which is one of the differences between QuickLOAD and GRT: The drop-down menu that selects the gas sealing and bore friction DOES NOT affect the initial pressure (start pressure) as I had assumed they did. In QuickLOAD's model, bore friction cannot exceed start pressure. This is not very realistic, particularly in rifles, for which friction peaks when pressure peaks due to all the acceleration g-forces tending to upset the bullet outward harder against the bore. So friction actually is a function of pressure that is in addition to the start pressure friction to engrave the bullet. You can, however, compensate for gas sealing in QL by raising the start pressure. Its model for long barrel friction, which occurs after the pressure peaks, is then pretty good, and pressure-induced friction can be modeled by adding a few percentage points to the bullet weight. But GRT appears to keep all that separate and seems to have (I need to evaluate this more) a better friction model than QuickLOAD that keeps them independent variables.
Once I found the start pressure was independent of the gas sealing model, a whole new range of possibilities opened up.
Finally, going back to post #1, the 230-grain load with 5.3 grains of 231/HP38 was reported in the Shooting Times Magazine article to have a velocity of 724 fps, and that number seemed to match what Aguila Blanca had measured. If I had just thought back to personal experience, that would have seemed low. So, when in doubt, get a second opinion. I looked up Hodgdon's data for the same weight bullet in their 5" test barrel, and there 5.3 grains of W231/HP38 is listed as a maximum load and they report 834 fps and 832 fps for lead and jacketed bullets, respectively. That's 110 fps faster than the Shooting Times number and Aguila Blanca's similar numbers. That difference accounts for most of the apparent error first seen in the GRT numbers. It has to be born in mind that the QuickLOAD and GRT models both, unless you change them, assume test barrel-like dimensions, which are minimum in chamber size. Real chambers can be a LOT sloppier, as you can see from the slide breech face to barrel extension gap in a lot of production 45 Auto guns. When you include the tendency to see a lot of primers unseating bullets to increase the powder space, I think the discrepancies are pretty well explained.
In GRT I put a lead bullet using the physical dimensions of the Sierra Match 230-grain RN FMJ bullet by setting the gas sealing and barrel friction to soft lead. I lowered the start pressure to 1160 psi. I lowered the default case capacity from 27.8 grains H₂O to 26.0 grains, which matches my measurements of unfired 45 Auto brass because I think QuickLOAD is correct that at low pressures where the cases are not pinned hard against the chamber wall you do not see so much expansion of the brass at the pressure peak. I gave it 5.3 grains of 231 without altering the model. I gave it a 5" barrel to match the Hodgdon test barrel. I gave it a 1.200" COL to match Hodgdon's COL. The result is as follows:
That's a pretty darn close match for a computer model, I think.
Based on this, the 6.1 grain loads from the ST article would run about 26,145 psi in the Hodgdon test gun, so I added the load warning to the first post, as that's about 14% above the SAAMI +P MAP of 23,000 psi for 45 Auto. Not yet to the proof load range (31,000 to 33,000 psi), but enough to beat up a gun if you fired it much.
Aguila Blanca said:
I discovered it is the same in the Advanced Interface. It is just that as the way the load window comes up after installing the program, the bottom of the bullet window is cut off by the top of the charge window. When I manually pulled the top of the charge window down, the full bullet window appeared and remains that way after exiting and restarting.
That window discovery leads to my second discovery, which is one of the differences between QuickLOAD and GRT: The drop-down menu that selects the gas sealing and bore friction DOES NOT affect the initial pressure (start pressure) as I had assumed they did. In QuickLOAD's model, bore friction cannot exceed start pressure. This is not very realistic, particularly in rifles, for which friction peaks when pressure peaks due to all the acceleration g-forces tending to upset the bullet outward harder against the bore. So friction actually is a function of pressure that is in addition to the start pressure friction to engrave the bullet. You can, however, compensate for gas sealing in QL by raising the start pressure. Its model for long barrel friction, which occurs after the pressure peaks, is then pretty good, and pressure-induced friction can be modeled by adding a few percentage points to the bullet weight. But GRT appears to keep all that separate and seems to have (I need to evaluate this more) a better friction model than QuickLOAD that keeps them independent variables.
Once I found the start pressure was independent of the gas sealing model, a whole new range of possibilities opened up.
Finally, going back to post #1, the 230-grain load with 5.3 grains of 231/HP38 was reported in the Shooting Times Magazine article to have a velocity of 724 fps, and that number seemed to match what Aguila Blanca had measured. If I had just thought back to personal experience, that would have seemed low. So, when in doubt, get a second opinion. I looked up Hodgdon's data for the same weight bullet in their 5" test barrel, and there 5.3 grains of W231/HP38 is listed as a maximum load and they report 834 fps and 832 fps for lead and jacketed bullets, respectively. That's 110 fps faster than the Shooting Times number and Aguila Blanca's similar numbers. That difference accounts for most of the apparent error first seen in the GRT numbers. It has to be born in mind that the QuickLOAD and GRT models both, unless you change them, assume test barrel-like dimensions, which are minimum in chamber size. Real chambers can be a LOT sloppier, as you can see from the slide breech face to barrel extension gap in a lot of production 45 Auto guns. When you include the tendency to see a lot of primers unseating bullets to increase the powder space, I think the discrepancies are pretty well explained.
In GRT I put a lead bullet using the physical dimensions of the Sierra Match 230-grain RN FMJ bullet by setting the gas sealing and barrel friction to soft lead. I lowered the start pressure to 1160 psi. I lowered the default case capacity from 27.8 grains H₂O to 26.0 grains, which matches my measurements of unfired 45 Auto brass because I think QuickLOAD is correct that at low pressures where the cases are not pinned hard against the chamber wall you do not see so much expansion of the brass at the pressure peak. I gave it 5.3 grains of 231 without altering the model. I gave it a 5" barrel to match the Hodgdon test barrel. I gave it a 1.200" COL to match Hodgdon's COL. The result is as follows:
Code:
GRT
Pressure Velocity
96.5% MAP 829.6 fps
20270 psi/17374 CUP
Hodgdon
Pressure Velocity
93.9% MAP 834 fps
19716 psi/16900 CUP
*psi/CUP ratio based on SAAMI MAPS ratio for the cartridge
which are 21,000 psi/18,0000 CUP.That's a pretty darn close match for a computer model, I think.
Based on this, the 6.1 grain loads from the ST article would run about 26,145 psi in the Hodgdon test gun, so I added the load warning to the first post, as that's about 14% above the SAAMI +P MAP of 23,000 psi for 45 Auto. Not yet to the proof load range (31,000 to 33,000 psi), but enough to beat up a gun if you fired it much.