Looking for opinions on putting a ACOG on a Bushy M4 project with a A3 flattop.What exactly is the difference in the base mounting point of the TA11 and the TA31?Do they both mount in the same manner and height?I see the eye relief is greater on the TA11.Do they both need a TA51 Trijicon mount or a ARMS 19S mount to fit on a A3?In my part of the world there is none I can look at,so I want to make shure to get the correct one for my AR,thanks for the replies Jeff

I believe they all mount in the same manner.  Get the ARMS 19S from [url]mstn.biz[/url] and you'll be happy ever after.  In my opinion the TA51 is no QD, or any mounts using thumb screws for that matter, if you tighten it enough to secure it from being loosened by recoil you'd have a hard time unscrewing it from your receiver without tools, the 19S is a true quick detachable solution.
But yes all except the TA01NSN will need a flat top adapter, the NSN comes with the TA51 adapter.  I think the 19S will mount it a bit higher than the TA51.
[img]www.imagestation.com/picture/sraid60/p0370c9afd7e6b9e0a0e2bdfa52d725c3/fc504696.jpg[/img]

You need either a TA51 (shit) or 19s. The ARMS is higher. You can fit a BUIS under it. On an M4, the TA11 is kind of big, but I cant use 4x ACOGs due to limited eye relief. Well, I could, but it aint too comfortable. Make sure you get the right BDC, and that you mount it the way it was designed, or the BDC will be off.

Thanks for the replies Duffy and Combat Jack,I still am unshure about the base of a TA11 and TA31.I understand the mount part(TA51&19S).But,is the bottom 1/3 of these scopes identical where it attaches to these bases?

goneglocken, the bases of these scopes are identical, they can all be mounted on a carry handle, or TA51, 19S, etc.  

[img]http://photos.ar15.com/WS_Content/ImageGallery/Attachments/DownloadAttach.asp?sAccountUnq=24926&iGalleryUnq=235&iImageUnq=16041[/img]

TA31 on an ARMS 19S.  Its SCHWEEET. [:D]

Great,I got the base part in my head now.Last question-What is the difference between the TA11 and TA31 besides 1.(overall size, 2.(eyerelief, and 3.(availablity, that would cause me to buy one over the other.I assume they both are close in acctual price paid vs.retail,and have similar donut/BDC reticles.

Field of view, size of reticle.  TA31 has a wider fov, the reticle also gets blown up a bit more than the 3.5x TA11.  Personally I can't tell the difference between 3.5x and 4x, but to most TA11 users, the biggest reason is the eye relief.

TA11 is 3x, TA31 is 4x.  They are both excellent buys, you can't go wrong with either.  These aren't like Ford vs Chevy, its more like Benz vs BMW.

The TA11 usually costs roughly $100 more NIB, but the "suggested retail" on either are almost always way more than what they really sell for.  It does pay to CALL and talk to a dealer; their selling prices are usually cheaper than their ads in magazines or online.  If you are patient, you'll find a nice used one on EE for a killer deal.  

TA11 3.5X
TA31 4.0X

TA11 Long Eye Relief
TA31 Short Eye Relief

TA11 1/4 MOA adjustments
TA31 1/3 MOA adjustments

TA11 5.56 and 7.62 reticles (use 7.62 reticles with 75 and 77 grain ammo)
TA31 5.56 reticles

TA11 Bigger
TA31 Smaller

To me I really wanted to get a TA31 because it seemed better and cheaper on paper.  In use I found I found the TA11 more user friendly and easier for me to use and caused less eye strain etc.  

Like I always say you MUST try these before you buy.  Big city gunshows always have ACOGs for sale and you should at least look through these before deciding.  Using other peoples is a better solution.

I wish I could use the TA31 but I have a TA11 on layaway.  I wish I could use a Glock too but it just has too funky a grip angle for me to shoot well with it.  This is a highly personal decision.

ta-31 on a ta-51 mount
"[img]www.lux55.com/penn/midm4.jpg[/img]"

Hmmm, mid length SIR... looks nice!