how do i know which size helmet to get for use with NVG? seems like all I see are medium, large and XL. um... heres to my dumb question.
Where/how do I measure my melon for the size I need? Im looking at the Pro-tech bravo ones, as cash is a bit hard to come by nowadays. I plan to use a rino mount with a pvs-14, soon to be ordered. Thanks!

Here is a cold link to the Ops Core page for their fast base jump.  It illustrates how the measurements should be taken for their product line, which may or may not be applicable to other products, but it least it gives you a starting point.

http://www.ops-core.com/FAST_Base_Jump_Military_Helmet_P27C6.cfm

ETA - Proper helmet fit is very important; try the actual product on before purchase if at all possible.

If you really want to save some cash, take a look at the Bell Faction.  I just got one for my mountain bike as a spare second and it is pretty comfortable.  I got it for $20 shipped off of Ebay.  I may bolt a mount up to it and see how it compares to my OpsCore Base Jump.  

You can get either a Norotos universal mount or a cheap USGI racket mount with the strap.  Use a molle mag pouch and fill it with batteries (or lead shot in a baggie) for a counter weight.  Also keep an eye out for an ACH chin strap to switch out the cheap one on the bell faction.  I got one for $5 or 10.

Measure your head above the ear at the widest point.  The see what helmet size is listed.  If there is a Sports Authority near by, they stock the Bell Faction.

I also have a Pro-Tec Classic which I don't like.  It is a tad tight in the front for me and the soft foam padding made it really hot for summer use.  The Bell has styrofoam padding which is much cooler.

What model are you going to hang on the front? If you are hanging 7's or 14's... you really need the lower neck web strap. Otherwise you will be holding up the front of your helmet with one hand...

I believe the ProTec Bravo comes with that harness standard (similar to a ACH pattern one).  But for a PT Classic or Bell Faction, you can always bolt on an ACH harness.  They are pretty cheap on Ebay.

Fat?  XL.  Not fat but male?  M/L  Female but not amazonian or have big hair?  S.

By Ops Core method I fell into the M/L measurements, but just barely. After getting the helmet I was unable to use it with hearing protection and it felt too small for me.



I ended up getting the L/XL and am much happier.





 

Dito Here.  My ops core sizing chart had me at the upper end of M/L.  The fine folks at TNVC told me to get the L/ XL absolutely.  I followed there advice and it fits like a dream.  I think the ops core chart is on the small side.

It's funny. TNVC told me the same thing when I asked as well. I found a great deal on a M/L on the EE and was too stupid to listen.



A good friend of mine now has that helmet and will put it to good use.



 

Same here. I was in the measurements for the M/L but it was too tight front to back and I had to sell it and buy a L/XL, which fits much better.