Do they work? Is it worth it? I was thinking of doing something like this to my Remington 700 rifle and 1100 shotgun. My wife complains of the recoil.

Did she shoot the 700 with PWS? Is it the kick or the noise?

That not my choice for recoil reduction on a 308.

Are you just target shooting or she plans to go hunting?  Since you reload you can make less powder reloads.

Shotgun forget it. Get reduced loads or a 20ga.

She said it helped but still complained later it was hurting. It's just for target shooting. I was going to try the JP compensator next for the 308 and use the surefire for my AR. I don't want to do much to that rifle so I was thinking of the mercury recoil or added lead or something.

Personally I wouldn't waste my money on a mercury system.  After years shooting trap and skeet I can tell you the body eventually gets used to the recoi, but you have to work at it.  If you don't want to give up on the 12ga. you might want to look into  a limbsaver  recoil pad instead of the mercury based systems. 

She said it helped but still complained later it was hurting. It's just for target shooting. I was going to try the JP compensator next for the 308 and use the surefire for my AR. I don't want to do much to that rifle so I was thinking of the mercury recoil or added lead or something.

Get a shoulder pad.... The JP tank brake is brutally loud and the concussion is nasty but works pretty good...

http://www.midwayusa.com/product/699899/past-super-mag-plus-recoil-pad-shield-ambidextrous

Is she holding the stock firmly into her shoulder?  A lot of recoil-shy folks hold the gun lightly or even a small distance away from the shoulder in the hope that it will kick less.  But it only makes it worse, since only the mass of the gun is "opposing" the recoil.

With the gun socked firmly into the shoulder, the mass of part of your body is added to the mass of the gun, reducing the total felt recoil.

I'd also look at the fit of the gun to the shooter --drop at comb, drop at heel, that sort of thing.

Then there's the noise thing, too, that someone mentioned.  Are you sure the muffs fit well?  Women wear earrings and have masses of hair which could affect the seal of the muffs to her head.  Eyeglasses will affect that, too.  Try using both muffs and plugs.

Terry, 230RN