View Full Version : Nikon 6421 Scope for my AR?

07-21-2008, 10:41 AM
I'm getting a Nikon 6421 that I'm planning to put it in my bolt action rifle (haven't bought the BA rifle yet :D, I just got the scope because it was a good deal that I cannot resist, brand new for $150).
My only concern is that my AR has a fixed/non flip front sight post. Is it gonna be a problem as far as accuracy since that front sight is on the way or not a problem at all? Any other suggestions may be, like using a higher scope mount or something?
So far I have Eotech 512 mounted and for 100yards shooting bench it's kinda hard without using a magnifier.
Thanks in advance.
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07-22-2008, 10:44 AM
That scope's just fine for an inexpensive, decent quality AR scope. Your front sight will be a shadow in the bottom of the scope at 3x, and will be unnoticeable at 9x. It bothers some people, but not many.

You'll need to get the right height and forward offset, depending on your stock length and cheek weld. People who shoot nose to charging handle with M4 style stocks need a lot of forward offset, while those who shoot more traditional cheek welds on longer stocks don't need as much. Some people are OK with rings directly on the receiver, but many need a one-piece mount or extended rail to put the scope further forward.

Most people like magnified optic centerlines to be about the same height as the iron sights, so they can use the same shoulder mount and cheek weld for both. Iron sights are 1.4" above the rail, and AR mounts run from 1.25" to 1.8" centerline.

Here's the Big List of AR15 one-piece mounts:


Here's a standard FSB in a Leupold Mk4 PR 3-9x40 at 3x:

and at 9x:

This is the setup used for these pics, with Leupold Mk4 high rings (1.06" centerline) - they should be super high, at 1.4" centerline, but this is worst case, as not many people shoot ARs with scopes mounted this low. This scope would be mounted way too far back for me unless I kept the stock extended pretty much all the way, due to the long eye relief of Leupolds. I like the eyepiece to be 0.5 to 1.0" ahead of the charging handle, but everybody's different that way.


07-22-2008, 2:32 PM
Great info Maxicon, thank you.
I have a Stag-15 2T model with 16" barrel , and the stock is LMT SOPMOD Stock, so what you think is ideal for mine?
VAPORIZER (http://johan-luis.tumblr.com/)

07-23-2008, 1:57 PM
It's hard to go wrong with the LaRue SPR mount if you're a bit behind the charging handle, and many people who shoot NTCH prefer the extended SPR-E. They're expensive (more than your scope!), but about as good as you get in terms of design and quality. Other great ones are the GG&G if you don't need a lot of extension, the JP if you don't care about quick release, and the ADM Recon or Recon X.

For under $100, the Armalite is a great semi-QR mount, but is too low for a lot of people at 1.25" centerline, and it doesn't have a ton of forward offset either. Most less expensive mounts don't have much forward eye relief, or have really fat rings that reduce your adjustment range a lot. The CAA DVSR is actually quite a good mount for $25, but only works well on 30mm scopes unless you buy full circle ring inserts for it. I've got a bench review on it here:

Best bet is to mount the rifle to your shoulder like you normally do, and have someone position the scope so you have a good field of view. Make note of where the eyepiece is relative to the charging handle so you can repeat the position and see where the rings would have to fall. You'll have to eyeball which mount would put it in the right spot or look for pics with a similar mount and scope combo (like at arfcom).

If you buy a LaRue and find it's not the right one when you fit it up (too much or too little extension), they're good about swapping for the one you need. Again, they're pricey, but hard to go wrong with.

Another option for a reasonable price is to get the YHM extended rail and about 1" centerline rings like Warne Maxima or Leupold PRW/QRW, which gives a lot of flexibility, at the cost of more attachment points to shift or loosen (not usually a problem if you get good stuff and tighten it well). There are pics of that setup at the bottom of my one-piece mount page. Doesn't look as tacticool as a LaRue, if that matters.