flightsimmer said:
The primary purpose of the large spring in the front of the slide is to return the slide to battery reliably after each shot. It is miss-named the "recoil spring" but in reality is the "slide return spring".
It has to be able to strip a cartridge from the magazine and close the slide, it need not be any stronger than that.
It does not control the recoil impulse as most believe.
While that is most technically correct in the operation of the firearm, the recoil spring can have a big impact on felt recoil by spacing out the recoil impulse.
It also can reduce how hard the slide slams rearward and forward.
I know that technically the slide only starts to move after pressure has dropped to a certain extent, but even that is subjective because I have seen that with really light or no recoil springs sometimes the slide will open while powder is still burning and you can see some flash out the ejection port. So it may not be a blowback operated action, but the recoil spring still provides resistance that helps there as well.
Too heavy or too light of a spring but close enough to still reliably cycle has a very different feel. The light spring slams the slide back harder, which gives more muzzle flip as it acts like a pendalum and has also got to be tougher on the firearm.
Too heavy of a spring but not too heavy to reduce reliable cycling increases felt recoil because more of the recoil impulse is delivered right as the round is fired because the slide is slower to pick up momentum or move and so is delivering the recoil to the frame sooner. It also slams the slide forward harder on its return. So it can actually cause both faster recoil giving more of a rearward jerk, and then also give more of a forward jerk when the slide slams forward from the spring power.
A spring that matches the load well can actually spread out the delivery of the recoil over a greater period of time, so it is still the same amount of recoil overall but over a broader space of time and is much less perceived recoil.
This gives much smoother shooting, with less jerking from either recoil or the slide slamming home.
