View Full Version : Scope mounting help?!?! Am I mounting my TR21 wrong?

09-23-2011, 9:32 PM
Gun- AR15 with freefloat handguard. Optic-Trijicon TR21 1-4x. Mount-ADM RECON

With the mount on the furthest forward slot of the upper receiver, I see a tunnel inside my scope and if I move my head a tiny bit I loose part of the picture. If I pull my head back(uncomfortable) I can see a clear picture through the scope.

Is it ok to mount the scope half on the receiver and half on the free-float handguard? Or to mount the scope only on the handguard? Or do do I need a mount with a longer cantelever? Like the recon X mount?

Also, whats a "NORMAL" spot for the rear eye-piece of the scope to sit in reference to the back of the receiver? IE: how far forward is NORMAL for a 1-4x scope to sit?

Thanks for any advice!

09-23-2011, 9:46 PM
The TR21 has pretty long eye relief so you should look at the extended mount. Great optic.

Droppin Deuces
09-23-2011, 11:18 PM
4.8" to 3.4" eye relief. If you are setting it all the way forward in the mount and still having problems, then you need a mount with more forward throw. I have a 3-9x scope with about 4.5" of eye relief on its lowest setting. It's mounted about an inch forward of the rear of the rear of the receiver, and it almost too close with the stock fully extended.

09-24-2011, 12:10 AM
I thank both of you. Looks like I need a longer mount.

Just to be sure....
The mount is ONLY supposed to go on the upper receiver...right? Never handguard?

09-24-2011, 1:10 AM
if you have a handguard that is mono. pic n a sec

09-24-2011, 1:17 AM
rail similar to thishttps://danieldefense.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/l/i/literailsup.jpg

and you will not regret buying from this company laruetactical.com

Droppin Deuces
09-24-2011, 6:41 AM
If you have a TR21, that ^^^ mount won't throw it far enough forward. You'd need the"E" version.


Alex M
10-01-2011, 12:59 PM
Sorry to thread jack but, would I need the Larue SPR standard or extended mount for a Nightforce NXS 1-4x with my nose to the charging handle?

Droppin Deuces
10-02-2011, 2:25 PM
Sorry to thread jack but, would I need the Larue SPR standard or extended mount for a Nightforce NXS 1-4x with my nose to the charging handle?

Just go to their site and look a the eye relief of the scope. Then hold your rifle with your normal cheek weld. Estimate the distance from your eye to where the scope would need to be set and figure it out that way.

Alex M
10-03-2011, 10:59 AM
Thanks for the help.

10-03-2011, 4:12 PM
If I understand the question correctly, you are asking if it's okay to attach front of scope mount on hand-guard rail and rear scope mount on receiver rail... since you have FF tube handguard, the answer is yes.

Or you can get an optional mount with extended forward rail as has been discussed in thread...

10-04-2011, 2:42 PM
Kemikalembalance: That is not a monolithic upper; it's an uninterrupted upper, but not monolithic. I'd avoid mounting the optic bridged from the upper/handguard. Even with as good as the Daniel Defense Lite rails are.

This is a true monolithic upper:



10-04-2011, 4:15 PM
^^^ what's wrong with mounting on a free float tube hand guard?