Any of you soldiers, Marines or sailors know?

http://lib.store.yahoo.net/lib/botach/ACHSizeChart.pdf

Worked for me.  I was 7 3/8 and wore large.  I think medium was a little small.

Yes

I'm close to that (7 1/8th) and wore a Medium.

7 1/2, large helmet. Still want a pasgt with viking horns.

Thanks!!

That was a PASGT, not a MICH or ACH, right?

I have a PASGT sizing chart that has the Large starting at 7 1/2 and going up, with 7 3/8 showing as a Medium.  This is really confuzzling as I've also seen sizing charts for the PASGT showing 7 3/8 as "Large".  Maybe they vary by maker?

It'll fit

I just found another sizing chart.  Shows that as some of the guys here say, it should fit.

Pretty sure I was issued a medium but somebody ran over it in Kuwait.  Supply guy ordered me a large because he thought I had a big head.  It actually fit better, especially with a beanie.  If I was going to hang a pvs14 off it I'd probably want a medium.  My ACH was definitely a large.
 

There's more to it than hat size...

Back in the day, the initial issue of the Kevlar had them using calipers to gauge a bunch of different measurements. Some folks would have had the size chart put them in a medium helmet, but things like the depth/height of their skull, ear position, width, etc., etc. would have the guys doing the sizing put them into a large.

Then, we quit caring about that crap, and just handed them out. You'd see guys come out of CIF with all sorts of problems, and then have to go convince someone that the kid belonged in a medium rather than the large, and so forth.

Somewhere, I've got the initial issue notes for those things--They were a lot more complicated than just hat size. The basic issue is that you need to be able to get the troop's head into the helmet deep enough to get full coverage for his skull, and on some people, a medium would leave them with critical bits exposed, so even if he fit into a medium, the guy was supposed to have a large. The sizing chart put me into a large, but I had to have an extra large to get the full benefit of the helmet's coverage. Another issue was how much distance there was between the webbing on the inside and the troop's skull--Not enough, and the force of a hit would be transmitted directly to the wearer's head. Which is why I'd strongly recommend that you upgrade the helmet with any one of the padding kits, especially if your head is really close to the inner part of the helmet with just the basic harness system in. The greater benefit of the ACH when it comes to trauma survival has a lot to do with the padding system, more than anything else.

This and the previous, thanks very  much.

I do understand that offset is very important.  

Thanks for the tip on padding, too.  Good stuff.  

Yes. That's my size.

That's a medium head size.

Yes, I have a 7 3/4 size head and wore a large.  Well, I probably still wear a large.