Just looking for input from those of you who have this setup. Do you find that your cheekweld is less than ideal when looking through the scope? I really like the benefits or the SIR and I think that the TA31 would be the best scope for that system. Am I wrong? Any input would be appreciated.

Also, if the TA31 was mounted on just the flat top with the TA51 mount, will it clear the ARMS #40 BUIS with new (non-sawed off) small aperature?

You need the TA31 on an ARMS 19A mount to clear the cut ARMS 40.  You need to move up to the TA11 and ARMS 19A to allow the ARMS40 Std A2 aperature to work (non cut). If you use the SIR Id use the TA51 mount with the TA31 since its lower.

New ARGuy has a nice M4 with SIR-M and he has a TA31 mounted directly to the rail via a TA55.
he is a great guy, and I think he will be more then glad to explain his setup to you.

I briefly mounted a TA31a to my SIR-m M4, but since the scope was designated for my SPR, once I got the SPR, I switched to the new gun.  I currently run a Aimpoint on the SIR.  While I had the SIR on TA31 on the SIR, i did not find the optic to be too high, although it is a bit high, but it still offer a decent cheek weld.  

I easily adapt to slight changes, so I may not be the best person to ask. However, no, I do not find it AT all uncomfortable. Not in the slightest. in fact, of all the AR's I have, and in all the configurations they have been in, with all the optics I have and have used, the T31 on a TA51 mount on top of the SIR is my favorite so far.

There are weird quirks about it. For example, the TA31 I have is designed to be used with a 20" barrel mounted to a carry handle. I use mine with a 14.5" barrel, mounted to a flat top.

The TA51 mount puts the scope at the propper eye level when mounted direct to a flat top. I have mine mounted to a SIR which is slightly higher.

These "quirks" if you will are not really disadvantages as far as I see it. Especially if you know about them going in. If you do, then you just have to learn to work with them.

If you are like me and can easily adapt to new things, go for it, I doubt it will bother you in the slightest. If you are sensitive to changes, you may notice the slight raise in the scope. It may bother you. If that is that case, maybe think about the new RAS II which has many of the same features as the SIR, but allows the ACOGS to be mounted at their normal height with the TA51 mount.

BTW, no, you can not mount a ARMS #40 under an ACOG using the TA52 mount direct to a flat top. You can however, use the ARMS #40 behind the SIR and mount the TA51 and ACOG on top of that, Thats the set up I have currently.

If the TA31 is typically mounted to the A2 carry handle, why would the ARMS #19acog throw lever mount on top of the SIR be too high?
It seems as if it would be almost the same height as if it were mounted on the carry handle.
Everyone I've talked to has said that the ARMS 19acog throw lever mount is to high to mount on top of the SIR rail system. What am I missing?
I'm planning on having MSTN put together a Colt preban M4 with a 14.5" barrel and pinned flash suppressor. I'm debating on what I should do about the front sight tower. I'd do the GG&G system, but do not want to wait up to 6 months. So I'm either going to leave it stock or put the PRI system on. If I get the PRI, I want Wes at MSTN to install it. I'd be afraid I'd mess it up.
My question with the standard forged sight tower, how much of the sight will be visible with the ACOG TA31 on top of the TA51 mount. Then, how much would be visible with the ARMS 19acog throw lever? Of course, this is on top of the SIR/m.
Sorry to hijack your thread, but I think these might be issues you might run into as well.
Thanks,
-Steve

Thanks for the input guys! I sincerely appreciate your honest opinions and I think you have convinced me that the SIR/TA31 combo is a good way to go (although convincing my wife is another matter [BD]).....time to give Donnie a call!

You're going to have a great set up and you are getting it all from a great company. Excellent.

Do you happen to know if this yet to be released mount will have throw levers? Man, I'm excited about this! While I adapt easily to change, my prefference would be to have it at the correct height over bore!

That's good news, thanks Wes!
Please let us know when it becomes available.

New-ARGuy, I took your advice and will go with the SIR-M/TA31 combo. Donnie had everthing in stock so I should have it built by early next week. Looks like my Christmas will come a little early![8D]

Cheers,
Aaron