So this weekend at the range I had 3 FTF out of 150 rounds, this makes it total to about 6 FTF since owning the gun and it has about 600 rounds through it now. The gun picks up the round but it doesn't fully go into battery. My thoughts are that it is from using 165gr. Bullets because I never notice it with 180 or 155 gold dots. I marked the magazine it happens most on, anyone ever experience similar problems with there gen 3 glock 23?

Morning J.

    Did a bit or research for you this morning and here's what I found that seems to make the most sense.
 
     Gun  has about 600 rounds through it now.
Gun w/ 600 rnds is broken in

    The gun picks up the round but it doesn't fully go into battery.
Lubrication ?
Cleaning, especially the ejector. Particularly between frame and where ejector protrusion would meet casing rim. Build up here will not allow the ejector to fully close inhibiting full battery/casing extraction?
weak Spring/rod
Try polish the feed ramp

    My thoughts are that it is from using 165gr. Bullets because I never notice it with 180 or 155 gold dots.
Blazer has a history of intermittent causes of failures in Glock.

    I marked the magazine it happens most on.
Some of the newer .40 magazines can cause failures to feed. In particular magazines with #8 followers that have 1 or 2 marked on the bottom of the back of the magazine tube. Some of the early ones with #9 followers can also have this problem. The problem is that Glock made the little protrusions of plastic at the front of the feed lips too big, they slow the rise of the top round and cause a failure to feed. The solution is to shave those protrusions down until the FTF's stop occurring, and perhaps a little more after they stop occurring just to be sure there won't be any problems in the future. You can remove those protrusions entirely and it won't cause any problems.  Just shave them down until the FTF's stop.
Seeing how there is a specific magazine where this situation occurs, my money is on the mag(s).

    Followers ( rebuilt ?).
With .40 magazines, tubes that originally came with followers #1(marked 1028) through #5 can only use one of those followers. Tubes that came with #6 through #8 followers can use any of those followers.
Tubes that came with #6 through #8 followers are supposed to be able to use #9 followers, but the #9 followers are wider on the part that engages the slide stop and they may fail to rise fully in the tube causing a failure of the slide to lock back. If that occurs you should see a rub mark on that part of the follower and you can shave it down until the empty magazine reliably locks the slide back.

JMHO
 

What kind ammo?.... Specifically

Thanks for the advice rocky, I'm hoping it's just the mag. I didn't really care at first because I figured it was maybe just breaking in but three times in one day is a no go for me.

The 165 ammo was American eagle and remington umc. I just picked up a case of 180 pmc to sample.

I say it's the AE ammo. I bought some from sports authority awhile back and I had the same problem.