My friends P226 will on occasion after sevral mags will fail to fully chamber a round.  The slide will come forward but not fully.  He can press on the slide and cause it to fully chamber and then continue fireing.  I know for a fact that he cleans and maintains the weapon very well so dirt or grime should not be the issue.  This occurs with the same ammo I shoot thru my P226,Winchester target ammo in the 100 round white bonus pack, except i have never had a single FTwhatever at all.  Both our weapons are 9mm if that means anything.  Could this be caused by a recoil spring?  Limp wristing? An out of spec slide? ETC?  Any help would be appreciated.  

Oh and by the way, both our Sigs are CPOs.  Like I said, mine has never given me a single problem whatsoever.

Recoil spring might be getting weak?

Quoted: Recoil spring might be getting weak?

+1

Get a spring pack from WOLF

- www.gunsprings.com/1ndex.html

(includes  recoil and firing pin springsd)

$25

Even if it doesn't solve the problem you will have spares for a long time

Good advice there -

WOLF is quality

Take out the recoil springs in both pistols and compare the differences alongside each other?
One of the ways to check visually is look at the distance between the coils. The weaker one "may"  be shorter.

Note also that if he has inadvertently reversed the recoil spring where the tight end is forward (not up against the recoil guide flange where it’s supposed to be), that can cause similar problems.

A new recoil spring seems like a good idea regardless.

I've got a bud that carries a SIG220 and he had the same problem.  If none of the above works, then have a certified gunsmith machine down the part inside the gun(where the handle meets the barrel inside the gun) at a better angle for the ammo to load.  He said sometimes a round would get hung up and I think it might be what you're talking about.  Hope that helps.