I have two types of 9mm ammunition that I have in my safe; Winchester 9mm Luger 115gr FMJ and Magtech 9mm Luger 115gr FMC. I decided to measure the OAL for the two types of ammo and found something interesting to me.
The Magtech was pretty consistent at 29.3 give or take few hundredths here and there. The Winchester, however; was quite rangy at anywhere from 29.2 up to 29.6. Again give or take a few hundredths.

What gives? I thought that OAL was precise. By the way this was not a reload question so I created this thread here, if you guys think it belongs elsewhere I will gladly move it.

Many thanks.

I have two types of 9mm ammunition that I have in my safe; Winchester 9mm Luger 115gr FMJ and Magtech 9mm Luger 115gr FMC. I decided to measure the OAL for the two types of ammo and found something interesting to me.
The Magtech was pretty consistent at 29.3 give or take few hundredths here and there. The Winchester, however; was quite rangy at anywhere from 29.2 up to 29.6. Again give or take a few hundredths.

What gives? I thought that OAL was precise. By the way this was not a reload question so I created this thread here, if you guys think it belongs elsewhere I will gladly move it.

Many thanks.

0.4 difference is not gonna make a difference much.  Did you notice any difference when you shot them?  As long as it feeds, decent accuracy, and no over pressure, then nothing to worry about.  I guess Winchester's QA is not that good...probably because of the demand for ammo.  Volume means decline in QA.

No its a suggested maximum.

1.169"

I have not shot the Winchester yet. I did not realize there was a leeway of 1mm. Ok going into the reloading (wont let it to far off track) I guess but does that same leeway apply for reloaded ammo?

I have not shot the Winchester yet. I did not realize there was a leeway of 1mm. Ok going into the reloading (wont let it to far off track) I guess but does that same leeway apply for reloaded ammo?

Yes, remember different bullet types (fmj, hp, etc) will have different oal...what you really gotta worry about is if it's too short that would cause over pressure.

Yes, remember different bullet types (fmj, hp, etc) will have different oal...what you really gotta worry about is if it's too short that would cause over pressure.

Excellent point regarding the different bullet shapes.  In my M&Ps  COAL for 9mm using 147 CMJ is around 1.125 give or take some, no problem.  With 147 LFP, max is 1.115, very much longer and the cartridge may start dragging and won't really spin when I drop check in my barrel.  With reloads, I try to start with the longest OAL the gun and mag will take and then adjust from there.  Like was posted above, longer OAL helps to reduce pressure, and additionally, may help reliable feeding.

Normal.  This is the difference from the mass produced ammo versus a match grade ammo.