I bought a used Rem-700 AAC-SD, It had an X-Mark trigger, and I had an extra old style Remington trigger, so I tried to install it, but discovered that the opening on the underside of the reciever, lacks the relief on the right side that allows part of the safety to pass through, so when installed the safety could not be used! Not sure what to do now, I'm not a machinist, don't have the tools to modify the reciever, guess I'll have to buy an expensive aftermarket trigger, but am not sure wich one of those will fit either? Sorry, I'm really frustrated to learn that Remington has changed their recievers so that the old-style Remington triggers can't be used.