These are original S&W mags, they have been kept full since day 1.
When the gun does not jam, it will lock open after last round.
Thank youall forthe help.

Now, from what you advised, I would say for sure the problem is
mag related. Sounds like the springs have taken a "set".
As I said before, get ya' a couple of new mags. I checked on the
S&W website, and you can order new ones there for about $40ea.
BTW, if you're going to leave your mags loaded all the time it would be a good idea to purchase a couple extra mags so that you can rotate 'em every month or so. This will help the springs last much longer.
And, as for some folks opinions on S&W pistols, don't pay it too much attention. I've owned a good many different S&W pistols over the years, and never had a problem with any of them (except my very first -one of the oldmodel 39's that I got in the early 70's - it didn't like feeding hollow points).
The S&W 6906 is a good gun!

Try new mag springs; If not try KY Imports Inc. # 1-800-718-3643. I bought 3 from them 2 months ago & they are orignal s&w mags. 12 rounder-19.99 + shipping

Don't throw your magazines out.
Don't trhow your pistol out.
Change your magazine springs.
A lot of factory magazine springs are cheap, with any such feed problem, th first thing you do is change your magazine spring.

Go here: http://www.gunsprings.com/Resources/welcomeNOF.html
Order the appropriate spring(s) for your magazine(s) and the problem you have described should be fixed.

Swap magazines, it should go away.

Thanks for the limk Briman! I was thinking along thesame lines, I tried to open the mag & getat the spring to stretch it.
I'm surethe aftermarketspringswould bea better fix. I was unable to get at the spring,first try, & wasafraid of breaking the mag. I'm thinkingto put one in a vice(gently) and try n drive the bottom off.[8D]
I could just get new mags , but I like to "hands on" with my equipment.I might learn something, worst case is I'll have to get new mags.

Check your owners manual, or download one here http://customersupport.smith-wesson.com/userimages/Pistol.pdf

it will give you directions on how to take your mags apart. I'm not familiar with S&W mags, but there usually is a small catch on the bottom of the magazine that needs to be pushed in so that the base can slide out.

Thanks again Briman! Good info there, I forgot I even had an owners manual.[&:]