Hey guys.  I am assembling a flat top carbine upper and am having a  hard time deciding between the knights RAS or the ARMS #45M SIR.  I will be using a TA-31.  Does the ARMS system raise the acog up too much for a comfortable cheek weld?   Also, is the TA-31 the best choice?  Which recticle is preferred?
Thanks for your help

glock
   u definitely wanna check out the picture thread for pics of MANY SIR and acog setups, as well as ras, ff ras, and ras 2.  hope you are happy with whatever system you decide to go with.

Stainless

The SIR doesn't put the ACOG too high, in fact it puts it aprox. 3/8" lower than when it was adopted by the military and placed into the carry handle. I'd get one of the slim line SIR's unless you want to hange a grenade launcher off the barrel, then you need the #45. I'd also get the #19acog or 19s throw lever  for mounting.
Good shootin, Jack

I have never used a SIR, but I did hold one at a funshow.  I do however, own a RASII,  and I love it!  Freefloats the barrel in a similar way to the SIRs but leaves enough of the original rail to use an ACOG.  The only downside as I see it is that it is more complicated to mount a target scope with the RASII, than with one of the SIRs.

[img]http://www.myweb.cableone.net/noknsean/Jpg%20image/eoras2.jpg[/img]

Tex78

That's a personal preference question really... it is like asking us if you like red or blue more. I second the advice to take a look at the picture thread to get an idea of whether the SIR will place the ACOG too high. If you are OK with a carry handle mounted ACOG, you will have no issues with SIR.



Best choice for what? The TA-31 is a pretty useful general purpose scope. I doubt you'll be disappointed but your intended use will play a role too. Check the Optics forum for many discussions of both questions.

I prefer the scope mounted to the correct height.  That would be the height the iron sights are currently located.  To find this you shoulder the rifle with your eyes closed, place your cheek on the stock and open your eyes.  If your looking straight down the scope or through your sights that is the correct height.  The SIR will not allow this.  You have to lift your cheek off the stock a little to get to the centerline of your scopes view.  If you are not worried about that then your fine with a SIR. This is not OK for me as I come from a bolt gun background and holding my head up to see through the scope is too unnatural.

If you dont go with the SIR check out the FF RAS and RAS 2.  The regular RAS does not free float the barrel and the lower rail can be a bit loose.

As for whats the best scope it depends on your tolerance of eye relief.  If you can deal with very short eye relief then go TA31.  If you need a more comfortable and longer eye relief get the TA11.

The prefered reticle for combat / 3 gun / ease of use with the BAC function is the donut.  If you plan on using 75 or 77 grain ammo the 7.62 reticle is best.  If you plan on using 55-69 grain ammo the 5.56 reticle is best.  I would ask more in the Optics section.

Thanks for the replys so far guys.  I plan on using the rifle for plinking, blasting jackrabbits and other varmints, and home defense if the need should arise.  They both look like great systems.  tough choices,as ive never had a chance to handle either setup.   Which one is lighter in weight?

Regular SIR is the heaviest.  Slimline SIR is much less but the weight of the SIR is more evenly distributed becasue the rail goes back over the reciever.  FF RAS is less than the regular SIR even with panels on it but most of its weight is in the big steel barrel nut that replaces the factory nut.

The 3 lightest are the slimline SIR, RAS and RAS2.

I think we still have the lightest railed fore end at 8.5 oz for the shorty.

Ashley
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