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Posted: 12/3/2008 5:54:33 AM EDT
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Hey guys I am working on building a varmint Ar and need some advice on scope mounts.
I am looking at a ARMS #38STD Swan Sleeve http://www.swfa.com/pc-6119-139-arms-38std-swan-sleeve.aspx and a set of high rings. My question is do I need the extended rail(scout rail) to mount a 3x9 Nikon? or is the #38TD enough? The eye relief is 3.6to3.7 thx for any input 
Sense a thread is not good with out pics here's my work in progress. 
http://i33.tinypic.com/zn651t.jpg |
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What kind of stock are you using? Is it a carbine stock, Magpul's PRS or an A2? You can always get a LaRue SPR 1.5 mount that places the optic further forward to give you more eye relief, or simply push the scope forward, as far as it would go while leaving room to adjust the elevation turret.
I don't think you'll need to extend the upper rail any. |
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I am going to be using a Ace skeleton stock.
I don't want to pay 45 bucks extraw to get a longer rail like this if I don't have to http://i35.photobucket.com/albums/d196/Bladeswitcher/RRAreceiver.jpg or this http://i13.photobucket.com/albums/a257/jee1/AR9x1.jpg If I went with just rings would some thing like this work? Burris Zee Quick Detachable 1" Rings http://www.swfa.com/pc-1190-327-burris-zee-quick-detachable-1-rings.aspx Or do I need some thing special? |
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I'd definitely get the extended rail, as the 38STD is just like mounting the optics right on the upper. Many people need magnified scopes mounted further forward, and for me, even the 38EX doesn't give quite enough forward offset.
The best way to tell is to figure out where the eyepiece needs to be in relation to the charging handle, and what it would take to mount it there. The rifle on the camo background has the eyepiece well forward of the charging handle (this is the way I need it), and definitely needs an extended rail, as you can see in the pic. Duffy's rifle has the eyepiece well behind the charging handle, which works for him, and is what you get with rings mounted directly to the upper or non-extended rails like the 38STD. For height, most people want their scope centerline to be around the same height as the iron sights, which is 1.4". My ARMS 38EX gives 0.48" more above the rail, so rings with a centerline in the 0.8-1.0" range would give the correct height to match iron sights. Note that some ring heights, like Leupold, are spec'ed to the centerline, while others, like Burris, are spec'ed to the base of the ring, and you need to add 0.5" (1" tube) or 0.59" (30mm tube) to get the centerline height. Also, you'll want to be sure your scope will clear the built-in BUIS. The new 38 series has the 40L BUIS built in, which would give it a folded height of 0.61", if it's the same as the stand-alone version. The older version had the standard ARMS 40 BUIS built in, which is nearly impossible to clear with a scope. To find out if it'll clear, measure the scope eyepiece diameter, divide that by two, and add it to the height of the BUIS above the flat top rail. That'll give you the ring centerline height above the rail you'll need to clear the BUIS with your scope. For rings on a riser, subtract the riser height, and that'll give you the height rings you'll need on the riser. Here's the Big List of AR15 one-piece mounts, which includes some info at the end about mounting on rings and rails: Big List of AR15 One-Piece Mounts |
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