Ah so this is how you do some hand editing to reduce polygons here is a German style helmet that i use for this tutorial GermanHelmet.ms3d click image above to see more detailed view.

Now you must look at the object it is actually 2 main surfaces that we are interested in reducing the inside of the helmet has one surface (we will almost completely delete this one) and the external helmet the original was very nice in the renderer at about 4000 but ours will be cool too and about 3000 polys less now we need to slice the top off  firstly you can make a sphere by hitting the sphere button under the model tab.

Once you have a nice sphere (13 stacks and 15 slices) makes a nice detailed sphere next we need to cut the bottom off the helmet by selecting a group (do this under the model tab and selecting face as the type of selection) and dragging it to slice the bottom of the sphere off. Now you can edit out the visor area, and strap as we need the face free for the model we are creating here. Note here that any curved surfaces are very poly hungry. Now lower the created sphere onto our sliced part of the helmet here is the result above with new vertices count of 1000. You can then go to the groups section and regroup the whole helmet and also apply our camo texture to it. Also note in the image the black surface underneath on the surface that we can't see when our models head is in it. Back to main page tutorial page Escape from Baxter Combine  mod for another non battlefield game.

and over to Battlefield rfa mod page and the BFV camouflage mod and the how to make a air defense souljahs helmet in Navmesh page