Even when recoil impulse is the same, it doesn't mean the same portion of the total equal and opposite momentum has to go into the slide, and its slide deceleration that causes much of the muzzle flip which exaggerates perceived recoil. A limp wrist avoids the sharpness of impact, but does that by decelerating the slide through the recoil spring more gradually, so more of the momentum transfers to the angular acceleration of the hand mass causing the muzzle flip to be even greater. I suspect that's responsible for the guns old reputation for kicking like a mule, when it's actually pretty gentle compared to many magnum revolvers.
For me, an eye opening example was getting and fitting one of the EGW flat bottom firing pin stops to on of my 1911's. It is Browning's original design, but was changed with the A1 due to complaints from soldiers about slide racking effort, which it increases. That increase happens because it starts cocking the hammer closer to the hammer pin where it has less mechanical advantage. But when you shoot it, that difference in mechanical advantage delays slide cycling, reducing slide velocity, reducing muzzle jump and lowering perceived recoil better than any buffer system I ever tried. It's not changing the total recoil impulse of the ammunition, but rather just what portion of it winds up in the slide on its way to counterbattery. When I first tried this out I was shooting plates with a friend who commented that from the side the muzzle was barely climbing. And maybe I'm just too used to the 1911, but we traded out firing mostly 200 grain LSWC's with 4.7-4.8 grains of Bullseye for firing some commercial 230 grain hardball that day, and I didn't really notice much difference between them with that arrangement. So getting recoil more straight back into your arms really seems to help tame perceived recoil a lot.
On peak pressure, QuickLOAD is predicting the Tightgroup velocity that Hodgdon shows rather than what Nick measured. It predicts the 231 load to produce 842 fps at 13,193 psi. To get a match to that muzzle velocity for 4.8 grains of Tightgroup, I have to fiddle the calculation. In the .45 Auto and other short chamber space pistol cartridges it is common for the primer to unseat the bullet before the powder gets fully burning, thereby effectively increasing the case capacity and shortening the remaining bore travel. In QuickLOAD this is easily modeled by reducing seating depth. In this instance, if I change the COL from 1.225" to 1.288" (1/16" reduction in seating depth), I get the desired velocity from the Tightgroup load. The peak pressure is then 13,043 psi. The 231 peak occurs at 0.2333 ms, while the TG peak occurs at 0.2552 ms. The muzzle pressure with 231 is 2232 psi. With TG it is 2193 psi.
I don't immediately see anything in those numbers to explain a significant timing change, even though I think that's what is affecting the recoil perception.
If I run velocity and pressure off the exponential relationships based on Hodgdon's data, I get 844 fps and 13,812 CUP for the 231 load and 877 fps at just 13,400 CUP for Tightgroup. If I drop the Tightgroup load to 4.56 grains (the only thing I can manipulate in those relationships to get a desired velocity) it shows the Hodgdon test gun would see 12,143 CUP and 844 fps. So, despite the numbers in the burn rate chart and in QuickLOAD's database, in this pressure range it appears that Tightgroup behaves as if it were the slower burning of the two powders, but with higher energy content per grain, getting higher velocity from a lower peak pressure by keeping pressure up higher toward the muzzle. The smaller charge weight used suggests higher the energy content. QuickLOAD's database confirms that, but only by a tiny amount in the lots Herr Broemel measured. But now we have a 14% peak pressure difference, and that could explain the slide picking up velocity less rapidly and slamming into the frame with less oomph. The bullet being pushed forward by the primer could get us to that lower peak pressure. If, in QuickLOAD, I extend the cartridge length to 1.316", I match the Excel peak pressure prediction using 4.8 grains instead of 4.56, but get 828 fps. Still, it seems like it's closing in on approximating what Nick measured. It's never going to match exactly because his lots of powder and primers and brass will all be a little different.
The Excel file I have, BTW, only predicts what the Hodgdon test barrel would do because that's what the data comes from. CUP and psi numbers aren't very far apart at these low pressures, but I am ignoring the difference and looking only at the percent differences.
For me, an eye opening example was getting and fitting one of the EGW flat bottom firing pin stops to on of my 1911's. It is Browning's original design, but was changed with the A1 due to complaints from soldiers about slide racking effort, which it increases. That increase happens because it starts cocking the hammer closer to the hammer pin where it has less mechanical advantage. But when you shoot it, that difference in mechanical advantage delays slide cycling, reducing slide velocity, reducing muzzle jump and lowering perceived recoil better than any buffer system I ever tried. It's not changing the total recoil impulse of the ammunition, but rather just what portion of it winds up in the slide on its way to counterbattery. When I first tried this out I was shooting plates with a friend who commented that from the side the muzzle was barely climbing. And maybe I'm just too used to the 1911, but we traded out firing mostly 200 grain LSWC's with 4.7-4.8 grains of Bullseye for firing some commercial 230 grain hardball that day, and I didn't really notice much difference between them with that arrangement. So getting recoil more straight back into your arms really seems to help tame perceived recoil a lot.
On peak pressure, QuickLOAD is predicting the Tightgroup velocity that Hodgdon shows rather than what Nick measured. It predicts the 231 load to produce 842 fps at 13,193 psi. To get a match to that muzzle velocity for 4.8 grains of Tightgroup, I have to fiddle the calculation. In the .45 Auto and other short chamber space pistol cartridges it is common for the primer to unseat the bullet before the powder gets fully burning, thereby effectively increasing the case capacity and shortening the remaining bore travel. In QuickLOAD this is easily modeled by reducing seating depth. In this instance, if I change the COL from 1.225" to 1.288" (1/16" reduction in seating depth), I get the desired velocity from the Tightgroup load. The peak pressure is then 13,043 psi. The 231 peak occurs at 0.2333 ms, while the TG peak occurs at 0.2552 ms. The muzzle pressure with 231 is 2232 psi. With TG it is 2193 psi.
I don't immediately see anything in those numbers to explain a significant timing change, even though I think that's what is affecting the recoil perception.
If I run velocity and pressure off the exponential relationships based on Hodgdon's data, I get 844 fps and 13,812 CUP for the 231 load and 877 fps at just 13,400 CUP for Tightgroup. If I drop the Tightgroup load to 4.56 grains (the only thing I can manipulate in those relationships to get a desired velocity) it shows the Hodgdon test gun would see 12,143 CUP and 844 fps. So, despite the numbers in the burn rate chart and in QuickLOAD's database, in this pressure range it appears that Tightgroup behaves as if it were the slower burning of the two powders, but with higher energy content per grain, getting higher velocity from a lower peak pressure by keeping pressure up higher toward the muzzle. The smaller charge weight used suggests higher the energy content. QuickLOAD's database confirms that, but only by a tiny amount in the lots Herr Broemel measured. But now we have a 14% peak pressure difference, and that could explain the slide picking up velocity less rapidly and slamming into the frame with less oomph. The bullet being pushed forward by the primer could get us to that lower peak pressure. If, in QuickLOAD, I extend the cartridge length to 1.316", I match the Excel peak pressure prediction using 4.8 grains instead of 4.56, but get 828 fps. Still, it seems like it's closing in on approximating what Nick measured. It's never going to match exactly because his lots of powder and primers and brass will all be a little different.
The Excel file I have, BTW, only predicts what the Hodgdon test barrel would do because that's what the data comes from. CUP and psi numbers aren't very far apart at these low pressures, but I am ignoring the difference and looking only at the percent differences.