There's another way to look at it.
If the peak speed of the recoiling rifle is 1 metre per second, which sounds plausible though it's a guess, then how long is the recoil pulse? If it was all over in 10ms, then the average acceleration during that 10ms would have to be 100m/s^2 for it to reach that speed in that time. That is "only" 10g but it's an average. A springer both recoils and surges forward before the pellet leaves the barrel so peak g will be much higher. 1 m/s may be conservative too, but as I say I don't know, it's just a nice figure for the maths.