I agree with @RickM that adding a little loft can really help, but you also have to watch your spin numbers when you are adding loft. Adding loft also usually adds spin so if you have a tendancy to balloon your drives then you are probably going to want to worry more about a more possitive angle of attack and get your trajectory from that, but if spin isn't your problem then loft up and give it a shot. Another thing to look at is are you in the center of the face with most of your drives if not shortening your driver shaft can help you find the center of the face, and that in and of itself can help you gain a good chunk of yards. One other thing is turning your front foot toward the target like 20 or 30 degrees can help make it easier to fire your hips through and that will add a few mphs to the swing speed. I'm a big fan of the if I can pick up 5 yards here and 5 yards there in a round that will add up to a couple of strokes haha. Best of luck. I am a huge fan of getting fitted for shafts it is the single most important part of the golf club in my opinion.
We will assume a few things going forward
1) you are standard issue golfer.
2) you are using the proper golf ball
3) you are getting roll from the driver.
That said a few things that can make an immediate effect. A higher quality of strike meaning increasing your smash factor. That is accomplish easily by choking down on the driver and hitting in the better part of the club. this is assuming you are not way tall
Once the proper length is found then you can go on to the other parameters Like loft, flex etc. Standard golfer usually plays a driver that is too stiff and or has too low of loft.
The XR16 although a nice driver is not a great driver. An older big bertha alpha or and EPIC driver can also make for some distance. I did a review on the epic verses my BB aplha gamer and was blown away by the difference.
I would look for a Callaway fitting center near you even if 100 miles out and make a day of the visit, it would be worth the drive(r). I have folks drving that far to see me due to the lack of qualifed guys in their neighbor hoods.
@jimm9fa7 I agree with you up to the XR16 not being a great driver. I got rid of the XR 16 Pro for the Epic SZ. While the Epic is more forgiving the XR16's length is still better. I make good contact with my driver and have good launch numbers Ball Speed around 180 consistantly launch angle around 14 degrees and spin between 1900 - 2400 rpm. Very seldom do i miss hit my driver. I played the last month of this last summer with the Epic SubZero and I don't think I missed maybe 3 fairways all month with it. My Epic driver while straighter on every shot is 10 yards shorter consistantly. My driver is always a weapon for me so i'm actually going to buy the XR16 pro off the preowned site for next year. Just because the epic doesn't compare to the XR16 Pro if left and right isn't your problem.