Rimfire Artist , "I'm guessing the difference was that they have to put a much stronger spring in the 3.5" chambered guns. Trying to shoot light loads in one of those is asking for failure."
The Kick-off recoil springs certainly felt stiffer to me in the Xtreme+ versus the Xcel target gun, but I never checked the difference as I sold the Xtreme+ before I the Xcel target gun came in.
As per the spring on the front of the gas piston, when you get a variety of custom springs to tune your poorly ejecting auto, you typically use a stiffer spring than stock to make it eject properly. The stiffer spring will hold the gas bleed system closed or closed longer so more gas goes into working the action....ejecting the fired case and reloading the gun with another cartridge....or what even takes more gas is to open the action fully so the bolt stays open after the last round is fired. A weaker spring will bleed more gas forward where it is wasted energy...but will prevent damage to the operating mechanism of the semi-auto from being over-pressured (over gassed).
The maximum pressure for a 12 ga 3.5" shell is 14,000 psi. For all shorter 12 ga shells, it's only 11,500 psi. I'd never buy another 12 ga with a 3-1/2" chamber for my use. I'm not a waterfowl hunter, just a target shooter when using a 12 ga and mostly shoot 7/8 or 1 oz light target reloads. I do my upland hunting behind our Vizsla with my 16 and 20 ga SxS doubles so the 12s never see field time.
