9 1/2 years ago (how time flies), I posted about modifying a 3rd gen 59XX/40XX curved back grip for installation on a 2nd gen model 659:
3rd Gen grips on 2nd Gen Pistols (with pictures)
Most of you have seen it by now.
Well, a couple of days ago, Forum friend (and all-around good guy), walter o sent me a PM asking about installing a 6906 grip on a 669.
At the time of the original post, I had a 6906 but no 669.
I had conjectured that they seemed similar and I privately vowed to try it one day.
In the intervening years, I acquired a 669 and with Walter's amicable suggestion, I found some time to try it.
As there are no templates or guides to this mod, it took several hours to accomplish, what with making a few cuts and trying it on, taking it back off, making a few more swipes with the file and trying a fit again.
It reminded me of fitting a new sear release lever, i.e. putting it on, testing, taking it off, filing a few swipes, putting it back on, testing, taking it back off, etc., ad nauseum...
I chose to leave the Dremel (aka, "The Devil's Paintbrush"

) in the toolbox and just go with files and sandpaper.
Here are some pictures with results.
6906 and 669 as original:
669 with 6906 grip installed:
That Brownell's tool in the foreground is a special tool for removing 3rd gen grips.
It works very well.
Although I usually just take them on and off with my fingers, I had to put the 6906 grip on and take it off so many times, I gave my fingers a break.
I also have a yellow handled version for the single stack grips.
Again, I rarely use them but I found them new and only a few dollars each on GB many years ago, so I couldn't pass them up.
Here's a picture of the 6906 and 669 grip frames side-by-side to illustrate the differences in the grip frame profiles of the two:
You'll probably notice the ledge for the mainspring cup mounts protrude more on the 669 and the attachment angles are different, hence all the cutting and trying.
Here's a picture of the modified 6906 grip with the modified 5906 grip:
I was pleasantly surprised to discover that the contours of the mainspring cup mount on the 669 matched perfectly with the contour of the 6906 grip.
Lastly, here's a picture of the inside of the 6906 grip, trying to show some of the modifications:
It was necessary to cut away for the mainspring mount as well as file away some of the two ribs which contact the 669 frame, and also relieve a little on both sides of the grip beneath the beavertail to allow the grip to fit close.
I also needed to open up the radius around the mag release button and cut back a little behind the sideplate where it meets the slide stop.
All modifications were to the 6906 grip and absolutely none to the pistol.
The 669 3-piece grip will not readily attach to the 6906 frame without modification.
In a similar vein, when I built the world's slimmest 3rd gen (or 1st/2nd gen for that matter) I did modify a set of 469/669 grips to fit:
Slenderizing the Slim. A 3914 story (with pictures)
All three mods were fun (yet undeniably tedious) exercises to demonstrate the amazing adaptability of this series.
Hope you enjoyed this and are perhaps incentivized to try something like this yourselves.
John