Editor’s note: For those of you who have been following this series, in the last episode, we completed the build of an Aero Precision M5E1 AR 10 Upper. In this, our last in this series, we’ll customize the rifle with a Primary Arms 4-14x44mm optic, an LMT buttstock, a Vickers Combat Applications Sling, a Geissele SSA-E trigger and a Magpul LR/SR Gen 3 “PMAG 10”. Once complete, we’ll take the gun to the range and see how our homemade rifle performs.
One of the most crucial decisions you’ll make on a long range rifle is choosing an optic. For this build we wanted value for dollar and we chose the Primary Arms 4-14x44mm with an ACSS HUD DMR 308/223 reticle. With the PA 4-14X44 FFP scope, priced at $259.99, you get an affordable optic that will allow you to get MOA groups at 100 yards (or nail the gong at 600 yards). We used PA’s Deluxe Extended AR 15 (30MM) mount which worked perfectly and at $50.99 was also priced right.
The reticle (with a center-chevron and horseshoe) is illuminated and comes with a zoom and decent glass.
The fit/finish on this item is excellent and the turrets click in solid, tactile increments.
The illumination of the reticle is decent. Between each incremental increase adjustment is an “off” notch. I found most of the time, during a sunny or even cloudy day, I really didn’t turn on the illumination but it’s there if you need it. The parallax adjustment was smooth and handy to have. The magnification change was a bit stiff but it did the job.
Some folks will dis China-made scopes but he quality is getting better and better and it’s tough not to like the features you’re getting with the modest price. The quality of the glass is reasonable enough for most end-users. For really good glass from Europe, the US or Japan, you’d need to shell out at least 4x the cost of this scope.
The optic comes with a three year warranty and PA is really good at backing up their products.
Our second acquisition was an LMT SOPMOD buttstock. I needed something with plenty of real estate that would afford a solid cheek weld to help manage the kind of recoil afforded by a .308 round. There are less expensive clones such as the B5 Systems SOPMOD, but the LMT SOPMOD is the gold standard, used by U.S. Special Ops Command, the Army, U.S. Navy, Air Force, Marine Corps and other government agencies.
The stock has a very substantial feel about it.
It’s made as one piece, and built like a tank. In addition to being ergonomically correct there’s a substantial rubber butt plate that reduces felt recoil and offers a no-slip surface against clothing, web gear and body armor. The stock fits snugly–there’s no wobble in the least. There are quick-detach sling swivel mounts on either side and removable storage tubes that will keep the interior dry up to 66 feet–but who’s counting.
If you jettison the tubes you’ll save another 50 grams, bringing the weight to a very respectable 307 grams. At $200 it’s expensive, but the genuine article. (I can understand why they make clones of this).
To get the stability I needed to shoot the rifle offhand a sling was obligatory.
The item I had in mind was the Vickers Combat Applications Sling which is also top flight. (There are 250,000 in use across every branch of service). Designed by tactical guru, Larry Vickers, it sports a pull tab that allows you to make adjustments on the fly. This option is handy at the range, but if you’re in the field and need to attend to business quickly and without distraction, it’s crucial.
Along with the sling, I got some hardware from Blue Force–a heat-resistant Universal wire loop and a rail mounted fixed loop. The wire loop, which is a non-marring, nylon-coated stainless-steel cable, has a socket for use with push-button QD sling swivels. A very popular set up for AKs, it also came in handy with this rifle.
Why? I like to mount the sling as far up on the rail as possible and the most forward socket on the handguard wasn’t far enough to my liking so I simply threaded it through the handguard and popped in the QD sling swivel. Voila!
If you’re interested in a secure setup for a one point sling you can attach a rail mounted fixed loop and then affix your sling directly to the mount. Of course you’ll need a smallish picatinny rail on the handguard to fasten down the fixed loop.
The final upgrade to this project is the was installing a Geissele SSA-E trigger. I was intimately familiar with the SSA trigger which I installed on an AR 15 lower a few years back and loved it. However I wanted to take this build to the next step. In my experience one needs a precision trigger to do precision shooting.
The SSA-E (Super Semi-Automatic Enhanced Trigger) is just that. This finely-tuned semi-automatic-only version of their full-auto, two stage combat trigger is used in the U.S. Special Operations Community. It’s perfect for target shooting too. It has a little bit of take up (about 2.3 lbs) and breaks crisply at 3.5 lbs.
It’s easy to add to y0ur lower. Geissele has the springs installed on the assembly, which is very convenient. All you need to do is drop it in. It allowed me to shoot some excellent groups and I admit I’m not the best rifle marksman. You can double on this but if you spend some time, this too will pass. That said, what’s great about the SSA-E is its predictability. When you hit the wall you know exactly what to expect–when the trigger will break. Wow.
On to the Range
Now that we had a complete rifle, we grabbed a couple of Magpul LR/SR Gen 3 “PMAG 10s” stuffed them in the bag and headed out to Kokohead Range, which butts up against the side of a long dormant volcano. I chose the PMAGs because one of the lowers, the James Madision Tactical, was actually engineered to work specifically with PMAGs. In fact the aesthetics of the lower perfectly match the pattern on the PMAG.
The ten round PMAGs were ideal to shoot off the bench. Anything longer would get in the way and considering that the municipal range only permits up to five rounds, there’s really no point in using anything with a larger capacity. Magpul says the one of the big improvement is an anti-tilt, self-lubricating follower which makes for increased reliability. The magazines are inexpensive and turned out to be quite dependable and are of course compatible with the DPMS platform.
The good news was that we evidently we put the gas tube on correctly. The rifle fed and cycled dependably all day–there was only one stove pipe. The BCG was a bit tight but with a new gun, that would not be unusual.
We let fly a few boxes of rounds downrange but had trouble getting consistent groups, even at 50 yards. We’d get a couple of decent shots and then inevitably a flyer up or down. There was no rhyme or reason to it. We made sure it the optic was secure and even took it off and tested the rifle with iron sights. We swapped out the lowers to boot. Nothing seemed to affect our groups, which were as lousy as ever.
At the end of the day we started to have doubts.
Did we tighten the barrel nut too much?
Did we screw something up in the building process?
We let the barrel/upper assembly sit for a week before we disassembled it and re-torqued at 60 ft lbs. We used 2 different torque wrenches and both of them agreed as to the amount of torque applied, which was reassuring.
Back to the range again. This time we put a tripod on the rifle and made sure we sandbagged the buttstock. Our groups were noticeably tighter and at a 100 yards were getting less than 1.5″ groups from 130 gr and 168 gr American Eagle ammo. Whether the difference in the improved accuracy was the result of re-assembling the barrel or simply shooting the rifle more skillfully (or both) I don’t know.
Although the rifle was noticeable more accurate the second time around, it didn’t cycle quite right. The brass often came looking like a dented automobile fender. So after a conversation with tech support at AP we went back to the laboratory and refitted the gas tube.
All systems go.
Then, there was another issue that we needed to resolve.
The front pivot pin on the James Madison lower would begin to shift, acting as if it were going to disengage from the upper after a few rounds. We had to pop the pin back in but inevitably it would continue to slowly retreat after we started firing again. Upon examination we realized the pin never engaged with the tiny indent pin, which in theory should keep in locked in. This was because the hole drilled into the channel on the pivot pin was a bit off, hence the indent never “popped into” the tiny recess.
We checked with Scott Franchette of James Madison and he said it was a rare occurrence but it was possible the hole was not properly aligned with the pivot pin. We could either drill a hole in the pivot pin so that it could engage with the indent or, Scott would be willing to send us a new lower receiver. We will eventually drill a hole into the pin or who knows, build a new lower. It was encouraging that James Madison is willing to stand behind its products.
Choosing the right ammo
Suffice to say, the ammo component of the equation is of great consequence.
We tested four different brands of ammo–Black Hills, Winchester, Hornady and (Federal’s) American Eagle in a number of configurations including 130, 150, 168 and 175 gr bullets. In general the rifle, which has 1 in 10 twist barrel, liked the heavier, match-grade bullets. No surprises in that department.
After putting a number of rounds down range, we were able to get sub moa groups. There was, however, an unexpected surprise in our little Gun & Tech ammo competition that I did not expect. The best group came from a American Eagle’s 7.62×51 168 gr Open Tip Match. Not that the others lagged by any means but generally American Eagle is not Federal’s “premium” ammo. The best explanation (full disclosure) on this particular group is that I didn’t shoot it. My good friend Roger Lukas pulled the trigger on that one. (Would the other groups have been better if Roger did all the shooting? I don’t want to think about it). We did shoot a bunch of 130 and 150 Gr American Eagle ammo which consistently got up to 1.5 to 2 ” accuracy but as expected the Match ammo did better.
That said, we got very decent groups from all the manufacturers. Ballistics Advantage, the manufacturer of the barrel guarantees sub MOA capability and I’d say that this is truth in advertising.
I learned a helluva lot building this rifle and my respect for gunsmiths has grown enormously. Smiths are obsessed with detail and for good reason. Sloppy work can turn into big problems. Even with a kit from a first class manufacturer like AP it takes some effort to do this correctly.
This is an accurate gun but if you’re looking for a target rifle you probably don’t want a carbine, particularly if all you do is shoot off the bench. That said, if you’re looking for an all round rifle suitable for home/range/hunting this is the ticket. Don’t think (despite what you see on you tube videos) that you’re automatically going to get great groups without substantial practice and a high quality gun rest. While the recoil is not as onerous as on a 308, nonetheless it is substantial and shooting well was a much harder process than I originally determined. This rifle humbled me in many ways.