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Trident Arms POF P415 P416 SBR Project


Custom Built POF P416 AR-15 Short Barrel Rifle (SBR) Project
Custom POF P-416 Suppressed SBR
This is a review of my Custom Built Patriot Ordnance Factory (POF) P416 Gas Piston AR-15 Short Barrel Rifle (SBR) Project.  This was one of my SBR project guns in my never ending search for that ultimate multi-functional SBR that balances long range performance and was short enough for close quarter room clearing with a suppressor installed.  There is nothing like banging your rifle against a door frame or telegraphing your entrance with an extra 20" of barrel & suppressor sticking out.
I really wanted to do this build with a piston system as opposed to a gas impingement. The piston system helps dissipate the heat and minimizes the fouling and maintenance.  So, I chose to use a POF upper and lower.  I have several other POF’s and believe they are revolutionary in their piston design and in my opinion are one the most reliable AR’s in the market.  They also have their Modular Rail System that I will use to help cover the suppressor.  I hate getting branded by a hot suppressor after pounding rounds downrange.
POF stripped P-416 lower
So, I ordered a stripped black anodized P416 lower.  After a long wait, I received it.  I quickly got it registered as a “Multi Caliber SBR”.  I wanted to make sure that I had the capability to change calibers if I ever had the need or desire in the future (See my article on the BATF Form 1 for more information on this process)
I took my new lower and carefully inspected it.  It is billet machined from a solid block of T6 aircraft aluminum alloy and the workmanship is flawless. The coating is uniform and evenly distributed and all engravings are crisp and easy to read.  I specifically chose a POF for several reasons.  1. It's a billet lower, 2. The one piece machined in trigger guard, 3. It has truly ambidextrous controls (bolt release & magazine release on both sides), just add a ambi-safety lever and it's a true ambi lower.  This POF lower is a quality piece of equipment.

After I received my approval, I picked up a P415-9-MRR-7SX-SBR upper.  This upper came with a 9 ¼” barrel and a 7” Modular Rail System. As usual, I fully inspected it, and as anticipated, found zero flaws. Once again, another quality piece of equipment from POF.  Their QA guy is definitely doing his job.

The operating system components consist of hard chromed gas piston, op rod, and a regulated NM3 coated gas plug that can all be easily disassembled for maintenance.  The upper and the rail are both billet machined from a solid block of T6 aircraft aluminum alloy.
Gas Plug, piston, & op rod
POF oversized heat sink barrel nut
It has a huge solid heat sink barrel nut that dissipates the heat 5 times faster than steel. The barrel is a chrome-moly vanadium (machine gun rated) “5R” 1x8 twist hand-lapped button rifled barrel from Rock Creek that has been contoured, fluted and nitrate heat treated.  It came with a nice Bolt & Carrier.  The carrier is nickel teflon plated 8620 integral keyed steel that is billet machined, heat treated/plated per Mil-Spec. The roller cam pin is NP3. A really nice set-up.
Now for the build.  I had ordered a POF lower kit from Dillon Precision and was really surprised to see it was nothing more than your standard AR-15 kit.  Oh well, lessons learned…. Never less it had the missing parts that I needed.  I installed my lower parts kit (mostly, as I didn’t use the trigger or the grip), a 3lb Timney Trigger w/KNS Antiwalk Pins (a must have on any AR) and a Falcon Industries Black Ergo Sure Grip.  I then installed a milspec buffer tube, spring, buffer and a collapsible Vltor EMOD clubfoot stock.  I also added a piece of foam tubing as a cheek buffer.  This is really nice to have when the buffer tube is cold.  This completed my lower assembly.
I am using a Gemtech G5 Suppressor and a Gemtech Quickmount Adaptor to keep it interchangeable with my other rifles. I had originally completed this build with my Gemtech Quicksand while I waited on my BATF paperwork also the G5 is 2.2" shorter.

I disassembled the 7” rail system from my new upper and installed my Quickmount Adaptor.  My new upper has a 9 ¼” barrel and my suppressor is another 7”; this will give me an overall barrel length of 15 ½” with the suppressor installed.  And, make the gun an OAL of 31 ½” (w/the buttstock collapsed).
I wanted a longer rail system to cover the majority of the suppressor.  A 12” rail would be perfect and only leave 3 ¼” of exposed suppressor.  No problem, I called POF to order one and discovered that they do not sell their rails separate from their proprietary upper receiver.  Also, they no longer make the 12” rail, they are now 11”.  So, if I wanted one, it was going to cost me $650 bucks. Well this is unacceptable.  I tried an Internet search and drew a blank.  What the heck?  Not wanting to get held up by this rail issue, I grabbed another P415 rifle with a 12” rail from my safe and decided I could swap the rails with it and save a ton of money at the same time.  This was easily accomplished by removing a few set-screws and sliding it off.  After I installed both rail systems, I discovered the short rail system on my 14” was pretty cool and really lightened the gun.  We’ll see how it acts at the range. The real drawback adding the longer rail system was it buries the gas block under the rail making it nearly imposible to change the gas setting from suppressed to non suppressed.  This is not an issue if I shoot this rifle suppressed all the time.  It also brings up a maintenance issue since you have to remove the rail system to clean the gas piston system.
Now I needed some optics.  For my back-up sights, I installed a pair of Troy Industries BUIS Folding Battle Sighs and then added a Trijicon TA31RCO-M4CP ACOG and put some ladder rails on it.  I mounted my new upper on the new lower to complete my build.
After a function check and inspection, I noticed some slight movement between the upper and lower.  This was easily corrected with an Accu Wedge.  POF should really incorporate a tensioning screw in their lower (see my AR9 build for an example).  The lines match perfect and there is no more slop.
This baby is really looking awesome!!! It’s a little on the heavy side, but all-in-all I could get used to it.

Now that my build was complete, I was ready to head to the range and test it.  I ran several hundred rounds through it and it performed and functioned flawlessly without incident.

The recoil was typical for an AR-15 and was equivalent to my other POF’s and AR-15's (even fully suppressed).  It reached out easily to 200 yards (the max distance at my indoor range) consistently producing a 1 1/2" group.  "I wouldn't want to be on the business end of this room sweeper!!!"

The suppressor responded as anticipated with greatly reduced sound levels at the gun.  The short barrel makes for a very maneuverable package, without suffering any drastic reduction in ballistic effectiveness.  This is another nice addition to my collection.

Here is a short video of my son conducting the test fire using Federal 5.56 mm 62gr M855 ball ammo:
Custom POF P-416 Suppressed SBR
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