Just came today from SWFA after 4 months.Dont know if they have more?I discovered that on a standard receiver flat top, no room to mount a A.R.M.S 40 under it without moving forward the scope,to far for correct eye releif,or using a SIR or something to raise it.The 40 is to high,even if it wasnt the back of the scope sticks out from the TA-51 base far enough to prevent you from getting it back all the way to the flip up .There is  No way to modify it by the looks of it so i took my GG&G A-2 flip up,which is low enough off another rifle and was able to cut,notch,and file the front of it to mount the scope all the way back with the acog on a TA-51 mount touching the GG&G for the best and or proper eye releif.

Some folks have had success mounting the ACOG/TA51/ARMS #40 combo, and other, such as yoursled have not. I dont know why or where the difference lies, but sometimes it works and sometimes it doesnt.

On the other hand, achieving "the best and or propper eye relief" depends a lot more on how you shoulder your rifle than weather or not the optic is mounted further up or back on the reciever. For instance, if I were to mount the ACOG as far back as you, the thing would be hitting me in the face with every shot. But then again, I usually shoot from a pretty aggressive, nose to charging handle stance.

Here's a pic of a TA31/TA51 mount that is fitting over a #40.
[img]http://www.imagestation.com/picture/sraid60/p6fb4706061aa4b63ca6a427f46233293/fc420faa.jpg[/img]

Do you have pics of your shooting posture for comparison?

The picture shown is way to far out for me.I shoot with the butt in the pocket whenever possible and not out on the shoulder,which is the only way it would of worked for me. My upper body ,weight lifter build might have something to do with it?where i have it now with no slot showing,still is further out then i would like,but i want to keep the BUIS on.I cant get my nose close to the charging handle without hurting my chest if the butt is in the pocket.This whole exercise was to get the eye releif to where acog recommends,hence,best and or proper, while in the pocket.I think now after writing this that people being muscular or very large may have the same problem as my self,where the stock always seem to long and nose grinding the chargeing handle only can happen with the stock out of position or prone.

I went with the #38 to make it work.

[img]http://home.earthlink.net/~martinmayhem/images/DSC00421.JPG[/img]

Martinmayhem,looks good,and guess what,silly me,if i use my acog on one of my prebans with tele-stock my problem disappears.Didnt think of that,but i mounted this optic on one of my dedicated competition rifles with reg stock to test it for awhile in competition at my local match to see for myself ,and i said this before,if BAC is all that.My final opinion will not necessarily reflect those of this website and it affiliates,unless i like it HA!

Thats not my gun... so I cant post pictures of me shooting it... Sorry.

sorry I was not too clear.  I was just curious to see a full body picture of your shooting stance using your rifle for comparison.  My NSN is mounted over the #40 (ocular end of scope; end of #40 and charging handle define a vertical plane) but it seems I am a bit hunched over when I shoot it. Perhaps this too is an "agressive" posture and is actually proper?