Seekins Precision SP3R M-LOK Rail Installation

This is the second review in a planned series that follows the progress of a build that I completed at the end of January.  The last review discussed the use of the Black Rifle Disease Engineering Dimple Jig and Gas Block Drilling Jig, both of which performed admirably both during that build, and during a second upper build that I did for a friend.

So now we move on to the second component I want to review: the Seekins Precision SP3R V3 Rail System.  Specifically, this review covers the installation of the SP3R.  I plan a review of its performance in March, after I've had a chance to run it a bit more.

The SP3R is a free-float rail system that uses a dual-nut system to provide a solid foundation for the rail without having to resort to shims for installation.  I personally like that feature, as the tedium of having to completely remove the barrel nut up to four times to get the timing right just doesn't appeal to me.  Instead of shims, the SP3R has a large triangle mounting nut, and a smaller titanium barrel nut.  To install, thread the triangle nut onto your upper receiver until it bottoms out.  On my upper (from Damage Industries) it actually went a little past 12 o'clock before it bottomed out.  Then back the nut out until the gas tube hole is just shy of 12 o'clock.

The SP3R's dual nut system.  Shown here with the triangle nut prepped for torquing the smaller titanium nut.

Insert your barrel and tighten the titanium nut hand tight.  Using a 1-1/8" crow's foot wrench, torque the titanium nut to a minimum of 35 ft. lbs. (maximum of 60 ft. lbs.).  You'll notice that as you torque the titanium nut, the triangle nut will move as well.  It may take some trial and error to get the gas tube hole lined up, but at least you don't have to take the nut all the way off.

The mounting system properly torqued and aligned.

Once the gas tube hole is aligned and the titanium nut is properly torqued, you can slide the rail over the triangle nut and being installing the screws.  Twelve T20 Torx screws secure the rail to the triangle nut.  Four 8-32x1/4" screws go in the top holes, and eight 8-32x3/8" screws go into the side and bottom holes.  Each screw should be torqued to 30 in. lbs. (NOT ft. lbs.).

Mounting screws going into the triangle nut.

Some things to consider with this rail:

It does not require a proprietary wrench.  It also does not come with a wrench, so if you don't have a 1-1/8" crow's foot, you'll need to buy one.  I try to buy Made in USA, so the wrench set me back another $50 from my local Mac Tools guy.

In addition to your standard torque wrench, you'll need a torque wrench that can torque the screws to 30 in. lbs.  I've had a FAT wrench for years for torquing scope mounts and such, so I just used that.
As stated above, trial and error is required to get the gas tube hole aligned.  It took me three tries, but I don't consider that excessive at all.

Over all, I found the installation simple, and I'm very pleased with it.  Now to get some rounds downrange and see how it performs!