Using the JBM Recoil calculator I get
JBM Recoil Output
Input Data
Charge Weight: 50 gr Muzzle Velocity: 2900.0 ft/s
Firearm Weight: 9.5 lbs Bullet Weight: 130 gr
Calculated Parameters
Recoil Velocity: 9.2 ft/s Recoil Energy: 12.5 ft•lbs
Recoil Impulse: 2.7 lb•s
for my Ruger #1 270 Winchester all the input parameters are shown in the above.
Now using the same program for the 358
JBM Recoil Output
Input Data
Charge Weight: 48 gr Muzzle Velocity: 2475.0 ft/s
Firearm Weight: 8.0 lbs Bullet Weight: 225 gr
Calculated Parameters
Recoil Velocity: 14.0 ft/s Recoil Energy: 24.3 ft•lbs
Recoil Impulse: 3.5 lb•s
Given those numbers and the perceived recoil I can only say that the Browning BLR must fit me better, have a better recoil pad, etc. than the Ruger #1. Muzzle blast I'm sure is part of the perception. The Ruger #1 in 270 Win has a 21" barrel and the Browning BLR 358 Win has a 20" barrel given the vast difference in expansion ratio probably factors into the perception. I know that the muzzle blast of the 270 in that shortened barrel length is a fierce fire ball that can be clearly seen in daylight. I'd like to photograph it at night as I'm sure that would be quite a picture. On the other hand the 358 has almost no muzzle blast in daylight.
But even with that the Ruger #1 270 starts to get painful on the shoulder as an accumulated effect after about 20 rounds. I've done numerous 50 round sessions with the 358 Browning BLR and never had a twinge of shoulder soreness?
So there is something going on that doesn't have a correlation to the Recoil Energy numbers.
I just did a quick check to see if JBM's program and the source you used since they yield the same numbers and both programs are doing something to account for the rocket or jet effect of the powder gases. Just using momentum gives a very simple formula where the (mass of the gun) * (recoil velocity of the gun) = (mass of the bullet + half the mass of the powder) * (velocity of the bullet). The assumption in this calculation is that the mass of the powder gas is evenly distributed along the barrel length thus placing the point mass of the powder gas at the midpoint of the barrel length which accounts for the factor of a half in the powder weight since even distribution would mean that the velocity of the powder gas a nano-second prior to bullet exit would be half the muzzle velocity of the bullet. Moving that divisor from the velocity of the powder to the mass of the powder is mathematically equivalent by the distributive property of multiplication. In formula form this proof can be written as:
(mass of the gun) * (recoil velocity of the gun) = (mass of the bullet * muzzle velocity) + (mass of the powder * velocity of the powder) where velocity of the powder = velocity of the bullet / 2 to account for the even distribution of the powder gas.
In this case for the 358 we have (56,000 grains for the mass of the gun where 1 pound = 7000 grains) * (recoil velocity of the gun which is the unknown variable we are trying to find) = (225 grains of bullet weight) * (2,475 fps muzzle velocity) + (48 grains of powder weight) * (1,237.5 fps velocity of powder gas assuming even distribution). Note: that the gravitational constant to convert weight to mass at the earths surface is 32.174 feet per second squared. When both side are divided by the weight of the gun this constant cancels out and can be eliminated to reduce the complexity of the equation. So to make an already too long of a story shorter we have:
Recoil Velocity of the Gun = [(Weight of the bullet in grains + Weight of the powder charge in grains / 2) * (Muzzle Velocity in fps)] / (Weight of the gun in grains)
with the load under consideration the bullet weight is 225 grains, half of the powder charge is 24 grains, and the 8 pound rifle(including scope, sling and ammo) = 56,000 grains or
Recoil Velocity of the Gun = [(225 + 24) * 2,475 fps] / 56,000 = 11.0 feet per second.
As noted above the computer program used to calculate the recoil velocity of the gun gave a recoil velocity of 14.0 fps. Which means that the jet or rocket effect of uncorking the pressure vessel (i.e. the barrel of the rifle) is being accounted for in some manner.
Just to make sure I don't lose all of this I'm going to post and finish in the next post.