Is it my gun, dirty ammo or my grip?

[CrazyGolfNut]

This may be a dumb question but; why does my right thumb get so dirty?  I shot 150 rounds of Remington UMC 9mm today in my M&P Shield.  When I was done, I was surprised on how dirty my right thumb was.  (I am right handed) Could it be the ammo, the way the Shield is made or maybe the way I am gripping the gun?  I did not notice this amount of dirt when shooting American or Winchester ammo. FYI my gun had been cleaned by a professional and only had 150 rounds through it before tonight.  Thanks in advance. 

[Mali]

I find that my thumbs get dirty, as well as my right index finger, when I shoot certain ammo over others. From what I can tell the exhaust of gases will occur through the slide rail area and the trigger area when the slide begins moving rearward to eject the case. Not all ammo does this as bad, but there are certain brands that burn dirtier and it shows on my hands after I have been shooting.

[CrazyGolfNut]

Sounds like dirty ammo.  I am new to guns so I am still learning.  Thanks.

[RobertH]

as long as you're shooting straight and the gun works, i don't care how dirty my hands get.

seriously though, whats your grip/stance like?  how's your groupings?

[shooter]

 Agree with RobertH. if you can hit with it, and your weapon functions well. getting dirty should  you be the last thing you worry about.   

[CrazyGolfNut]

as long as you're shooting straight and the gun works, i don't care how dirty my hands get.

seriously though, whats your grip/stance like?  how's your groupings?

I have spent a lot of time looking at videos so I think my grip is good and my groupings are getting better every time I shoot.  It sounds like it is just dirty ammo.  Thanks for your thoughts.