If the gun maker says don't use +P loads in the gun, and you use +P loads, forget ever getting warranty work done. That particular issue is one that EAA is particularly unforgiving about... People have had problems with slides and frame while shooting factory (non-+P) loads have had their warranty claims denied by EAA even though they never examined the guns. The nature of the problem allowed EAA to claim the gun had been using HOT loads, and they wouldn't discuss it further.
More importantly, if "protection" could be offered by simply changing out a recoil spring, I doubt that Tanfoglio would say, "don't shoot +P." Guns designed to handle +P rounds are generally beefed up throughout the guns's structure -- the gun maker doesn't just add a heavier recoil spring and says it's now a +P-rated gun..
About recoil springs:
The primary function of the recoil spring is to close the slide after loading a round,
not managing recoil or protecting the slide or frame. The Tanfoglio/Witness factory spring weight recommendation is 14lbs for all calibers in that frame size -- it's the same whether you're shooting 9mm, .40, 38 super, and 10mm. A factory 10mm load operates as a noticeably higher pressure than .45 +P, so there has to be some flexibility in the design.
A heavier recoil spring will, if you reload, keep spent brass from traveling so far it can't be found -- and that seems to be the practical reason for going to a heavier spring. But, as noted above, changing out the recoil spring to "protect" you or the gun from recoil force may be a wasted effort. Going to a heavier recoil spring won't necessarily do much to reduce accelerated wear or protect the gun from the extra force in a hotter load. That's because a heavier recoil spring stores more of the round's force than a lighter spring, and then slams that extra force back into the gun when the slide slams forward -- primarily through the slide stop pin. If the gun hasn't been designed to handle that extra force, the heavier recoil spring hasn't really dealt with the problem.
SOME of the damage to Witness guns seems to be due to slide or frame flexing -- and a heavier recoil spring isn't likely to CHANGE that.
If you're unconvinced and still want to shoot +P in that non-+P rated gun, consider a different option, in addition to (or in place of) a heavier recoil spring: use a heavier hammer spring. I suspect it will distribute the force being stored differently, and that may change what happens...
Using a heavier hammer spring also stores some of the force from the fired round (as the slide goes back), but reapplies it to the frame when the hammer drops, which is a bit later in the firing cycle than when the slide closes. The heavier hammer spring, in effect, helps to distribute the total stored force over a slightly longer period of time, and that can be easier on the gun. A heavier hammer spring, because it slows the slide a bit, will also help with shortening the distance brass is thrown, and the only place you'll really notice its presence is in the DA trigger pull. In SA mode, it won't be noticed all that much. If your DA trigger is already smooth, the heavier hammer spring may be a good option: it gives you the benefits of a heavier recoil spring without increasing the force the slide stop must handle at the instant the slide slams forward.
Personally, I've owned a number of Tanfoglio/Witness guns (including several .45s and one 10mm top end mounted on a Sport Long Slide .45), and I liked them a lot,. I don't have any at the moment, but I have become VERY WARY of EAA's Customer Service. If you've got to shoot +P loads, I'd look for another gun, and stick to factory loads or their equivalent in a Witness.
Unless you've got money to burn.
Re springs:
Check out this site: (
http://WWW.GUNSPRINGS.COM)
.
