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Posted: 6/6/2008 12:51:38 AM EDT
I am building my second ar15, this time a varmint version with a 20" DPMS Bull Barrel upper with a rail on the gas block.

Here is the Upper

Now I want to add a BUIS system to it along with a Armalite 1" 1 piece scope mount, and a Bushnell Elite 3200 10x40.

1. Does anyone know if there will be room for a BUIS

2. I like the promag BUIS that Cheaper than Dirt is Selling. At $100 for both a rear and front sight, I havn't seen a better deal. Hopefully I will never use the sights except for sighting them in before mounting a scope, so I do not care about anything High Dollar. If anyone knows any good sights for a better price please let me know.

Anyways, I was not sure if the front sight would seat to low on the gas block rail, or if it was designed to be used on a Forearm rail. In the Picture it looks like the front rail is very slightly lower than the rear rail, I didn't know if this would make a difference.

Here are the sites

Link Posted: 6/6/2008 10:04:22 AM EDT
Very few BUIS will fit under a scope in an Armalite mount.

Here's how to figure it out:

Measure your eyepiece diameter with any flip caps and divide that by 2.
Subtract that from the centerline of the scope mount.
This gives the highest BUIS that will fit under your scope and mount.

Using the DMS-1 as an example:

Eyepiece with flip cap diameter is 1.8".  Half of that is 0.9".  The Armalite centerline is 1.25", and subtracting 0.9 from that leaves 0.35" clearance.  The only BUIS I know of that will fit is the KAC 300M sight.

Here are some popular BUIS heights:

ARMS 40 - 0.950" folded (mine is 1.00" even)
YHM-9680 - 0.840" folded (mine is 0.850")
Matech - 0.75" folded
MI ERS - 0.750" folded
GG&G MAD - 0.625" folded
ARMS 40L - 0.610" folded
Troy - 0.460" folded
MI MCTAR-SPLP - .4375" folded
KAC 300m - 0.315" folded

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


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