Shooting Review: Adams Arms’ 5.45×39 Mid-Length Complete Upper Receiver

This review could not have come at a worse time to a better company & product. TFB requested the Adams Arms upper when 7n6 was plentiful. With the recent ban on cheap MilSurp ammo, the allure of 5.45 may be waning, but as a DI guy I walked away plenty impressed with the Adams Arms piston kit.


The Adams Arms 5.45 lower mounted to a standard AR-15 lower compared to a standard mid-length upper with carry handle and FSB.

The Adams Arms 5.45 upper mounted to a standard AR-15 lower compared to a standard mid-length upper with carry handle and FSB.

I never quite understood why 5.45 did not catch on as much as 7.62×39. It was consistently much cheaper, similar ballistics to 5.56, and lower recoil for like performance. During the “panic” 5.45 was still easily available and AK74’s did not see any where near the same inflation. Yet, many 5.45 kits have come onto the market, but only Adam’s has had any staying power. The Spike’s Tactical, Smith & Wesson, and other have waned. I would suspect this has much to do with Adams Arms’ piston system.

Mounted in the rest ready for zeroing.

Mounted in the rest ready for zeroing.

The Adams Arms’ 5.45 Upper

I was fortunate to be stationed next to Adams Arms at ShotShow 2014. There, I discovered that Adams was just releasing a complete mid-length 5.45 upper receiver kit. Keen to try the mid-length over the already released carbine version, I requested one for review. Adams sent me one of the first off of the production line.

Even though upper receivers do not have to be shipped to a FFL, Adams took care to ship in a nondescript box. The upper was packaged in a clear thick plastic bag, contained in purpose-made styrofoam padding. Included in the kit was the complete upper receiver (no iron sights, standard mid-length shielded handguards, 5.45 30-round magazine, and an increased power hammer spring for reliable ignition of old surplus ammunition.

The upper receiver was a standard matte black color with an even finish. The one-piece bolt and piston op-rod had a slick finish with a nice metallic sheen. The barrel is 16″, 1/8″ twist mid-length, government-profile, with a standard A2-style flash-hider. Adams uses a proprietary “LifeCoat” finish on the barrels and bolt for increased hardness and resistance to corrosion critical for long-term use with 7n6 and similar ComBloc ammunition. The barrels are supplied by their sister division, VooDoo Innovations.

Close-up of the gas block and barrel showing the VooDoo markings.

Close-up of the gas block and barrel showing the VooDoo markings. You can see some residue from the piston vent after about 500 rounds.

For the review, I opted to use one of my trusty SAA lowers (OEM’d by Aero Precision). It is a standard AR-15 lower with a Del-Ton complete lower parts kit and H1 buffer. It has been flawless in any put on the receiver to date. To start, I did not install the increased power hammer spring as I wanted to see how reliable it would be with standard lower parts.

The Adams Arms upper went on tight! The first time it was mounted, I had to use a brass hammer to push the pins through. After two more removals and re-mountings the upper fit on the lower fit and pins were removable by hand. As you may expect from this effort, there was no play between the two receivers.

The upper receiver with EOTech mounted. Note there is no light gap between the receivers. Solid fit!

The upper receiver with EOTech mounted. Note there is no light gap between the receivers. Solid fit!

It is notable that since Adams uses a piston, the bolt is spring-loaded to push forward during the unlocking phase. When assembling the two receivers, the shooter may have to remember to push the entire BCG forward so it does not stick out from behind the upper for easy reassembly.

The Adams Arms gas block is fully adjustable with four settings:

  1. “High” – Normal operations, non-suppressed. (I ran the review at this setting)
  2. “Low” – For suppressed shooting.
  3. “Off” – Manual action cycling required.
  4. “Remove” – Dis-assembly and cleaning.

The upper comes lubricated, but I like to run my rifles wet whenever possible. I added a bit more BreakFree CLP, broke open a tin of 7n6 and headed to the range.

A Lot of 7n6 Died to Bring You This Review…

For the range session, I mounted my trust EOTech for zeroing and general shooting. For accuracy testing, I used a Caldwell 7-Rest and Gander Mountain zeroing targets set up at 50 and 100 yards.

The manual of arms is the exact same for the 5.45 upper, which made it easy to get comfortable with quickly. Recoil is pleasant, in line with what one would expect from any mid-length upper. Shooting the 5.45 and a mid-length DI 5.56 back-to-back did not yield any appreciable differences on my “shoulder-meter”

A random shooter who provided his feedback on the rifle.

A random shooter who provided his feedback on the rifle.

Using surplus 7n6 and some Wolf I was able to scrounge a local sporting goods store, I set out to zero the rifle. At 50 yards, the upper came in over 20″ below my ACR and AR-15s (which are within a few inches of each other at 100 yards). Unusual, but with the optic adjusted the point of impact did not shift during the multiple testing days.

I used the 7n6 to originally zero the rifle. Shooting slowly and methodically, the surplus ammo came in to average 3 MOA groups across strings of fire, surprisingly good for surplus ammunition. The smallest group was 1.3″ across and largest was 5″. There was no noticeable difference with the Wolf.

The smallest group at 100 yards. I completely bonked the fifth shot and called it in my book.

The smallest group at 100 yards. I completely bonked the fifth shot and called it in my book.



Having “fun” during slow-fire with four different shooters. Here you can see what happens when you press on a non-free-floated barrel. Very consistent performance across multiple people.



Note- I opted to run the gun hard and experiment to see what works. When used per Adam’s manual with either the purpose-built 5.45 magazine or the modified PMAG, functionality was perfect. The synopsis below is purely my experimentation. 

Laser-etched logo on the upper leaves no doubt the origin of the rifle.

Laser-etched logo on the upper leaves no doubt the origin of the rifle.

As I noted earlier, I originally shot the upper with the stock AR-15 hammer just to see how reliable ignition would be. On my first range trip using the stock spring, I experience a light hammer strike about 1 out of 30-40 rounds across 400 rounds. Not bad considering the ammunition was made long before the rifle. After switching to the increased power spring, the remaining 350-400 rounds ignited 100%. If you plan on shooting the upper often, use the high-power spring. However, it did increase my 5lbs 10oz stock trigger pull to about 6lbs 7oz.

The real issue with 5.45 uppers is magazines. Compared to 5.56, 5.45 has a higher case taper, which when used with non-tilting followers can cause failures to feed “nose-dive” malfunctions when the rounds don’t feed fast enough. To test this, I used five different magazines outlined below:

  1. Included 30-round 5.45 Magazine
  2. Modified Gen 2 PMAG (per MrGunsnGear’s video here)
  3. Stock PMAG Gen 2 (Window)
  4. Stock PMAG Gen 3 (Window)
  5. Brownell’s STANAG Mag w/ Level Follower

Using the stock 5.45 magazine and the modified PMAG, functionality was 100%. I tested various round counts in the standard mags and below are my findings of reliable function. The Brownell’s metal magazine had more issues. I would suspect this is due to the increased friction between the rounds and the metal magazine body.

  1. (15 Rnds) Stock PMAG Gen 2 (Window)
  2. (16 Rnds) Stock PMAG Gen 3 (Window)
  3. (12 Rnds) Brownell’s STANAG Mag w/ Level Follower

Assuming the magazines were loaded at or below the capacities above, bolt hold open was consistent.

The three stock magazines were all NIP to try and eliminate variables during testing.

The three stock magazines were all NIP to try and eliminate variables during testing.

Example of a nose-dive malfunction from an overloaded 5.56 magazine. Using the provided 5.45 magazine, feeding was flawless.

Example of a nose-dive malfunction from an overloaded 5.56 magazine. Using the provided 5.45 magazine, feeding was flawless.

The rifle handled both the 7n6 and Wolf ammunition very well. 7n6 ejected consistently to the 4 o’ clock positon. Wolf was considerably weaker, ejecting to 5:30. Interestingly, each case mouth was dented from its impact with the brass deflector in exactly the same spot.


Case mouths dimpled in the same sport across spent casings. A sign of good consistency since steel cases cannot be reloaded.


After the Range

While there is some debate on the validity of using Windex or other ammonia-based products to neutralize corrosive primer salts, I opt to err on the side of caution and spray the weapons down thoroughly prior to putting them in the gun bag. While I left the rifle in the truck overnight, it showed no signs of corrosion.

The best way to remove corrosive salts is hot soapy water. Wish I had a bigger sink!

The best way to remove corrosive salts is hot soapy water. Wish I had a bigger sink!

One of the main advantages of piston rifles is the ease of cleaning. I must compliment the LifeCoat treatment. The bolt, bolt carrier, and piston op-rod where as simple as dunking them in hot soapy water and drying with a paper towel. The receiver and gas block needed the same soap to neutralize the salts and require the typical AR cleaning since they are not coated.

One Predictable Issue & One Surprising One

All piston-driven AR kits suffer  to one degree or another from what is known as “carrier tilt.” (Note, there are many ways to compensate for carrier tilt, but that is not in the scope of this review) In short, since the force driving the BCG is not in center-line both horizontally and vertically with the BCG, the force directs some energy in the direction of the entry force. Since the piston op rod drives hits top of the gas key, some force is directed downwards like a cantilever. This causes excess wear on the buffer tube (and in extreme cases, the buffer tube threads). The upper kit did cause some minor wear on my buffer tube after 750 rounds. Nothing major and if I were to have the upper permanently, I would get an anti-tilt buffer and buffer tube. Easy problem to solve.


The other issue was not expected. I first noticed it on the range when I pulled the BCG for a temperature test after 50 rounds (it was cold thanks to the piston system!). During the inspection, I saw some metal shavings on the cam pin. Thinking it was normal wear, I put back in for the remainder of the test. It was not until later during my first cleaning; I pulled it apart and saw a lot of shavings. Now curious, I looked in the upper receiver and saw that the steel cam pin was wearing against the upper receiver.

My guess is the spring rate for the bolt is not strong enough. I shot another 100 rounds and no additional wear was noticed. Looks like it maxed itself out.

You can see the shavings from the upper clearly on the cam pin and surrounding area.

You can see the shavings from the upper clearly on the cam pin and surrounding area.

The upper receiver. Note the slot now carved by the cam pin at the rear of the cam pin rotation area.

The upper receiver. Note the slot now carved by the cam pin at the rear of the cam pin rotation area.



The Adam’s Arms 5.45 Mid-Length Upper shoots great. It puts old surplus ammunition where you tell it with no argument. Its sturdy construction, piston driven system, and very cool coatings make this a strong contender for my dollars (retails for about $850). The problem is that it is hampered by the ATF’s rulings, which made the strongest argument for it largely moot. I would buy the 5.45 upper in a heartbeat if the ATF had not banned further 7n6 imports.


So, I have to separate the 5.45 from the review and look purely at the Adams Arms’ piston offering. Doing so yields an impressive piece of kit. The piston system significantly cools the receiver, offers no appreciable difference in recoil, adjustable gas for suppression, and only minor carrier tilt due to the one-piece BCG. You can find a kit the street for about $320, which is a good buy for those looking for its advantages. As someone who has always shot DI AR’s its hard to find fault with it other than the cash outlay. The cleaning is certainly easier!


Nathan S

One of TFB’s resident Jarheads, Nathan now works within the firearms industry. A consecutive Marine rifle and pistol expert, he enjoys local 3-gun, NFA, gunsmithing, MSR’s, & high-speed gear. Nathan has traveled to over 30 countries working with US DoD & foreign MoDs.

The above post is my opinion and does not reflect the views of any company or organization.


  • TheSmellofNapalm

    Great review. I’ve been following AA for a while and was hoping they’d get more attention. They’re relatively small and have a lot of ambition. Again, thanks for the in-depth review.

  • Giolli Joker

    Interesting product and very interesting review, thanks!
    (BTW, caption under third photo need the first “lower” to be replaced with “upper” 😉 )

  • Sam Schifo

    I have an Adams Arms 5.45 carbine upper that I got a couple years ago and I couldn’t be more pleased with it. I’ve had zero problems with it in the 1000+ rounds of 7n6 that I have put through it. I, however, haven’t experienced the problem with the bolt cam pin like Nathan did, maybe because mine is a carbine and therefore the bolt carrier gets more energy imparted to it and thus cycles faster. I haven’t seen any visible signs of carrier tilt either, that may be due to the fact that I have a commercial spec buffer tube though. At any rate, if someone is in the market for a piston AR, I’m going to recommend Adams Arms to them.

    • I had a similar experience as you, sam, with my adams 5.45 upper. about a 1000 rounds, no signs of carrier tilt and definitely nothing like the cam pin issue in the article. also I didn’t notice any corrosion and I sometimes went a couple months between cleanings. The other nice thing about the complete upper is that it comes with a more powerful hammer spring. My ak would have light primer strikes every 30-50 rounds, while my 5.45 ar never had one.

      • Sam Schifo

        I do enjoy having the extra power hammer spring, I’ve never had light primer strikes with my AA upper either. I have always cleaned mine after shooting it just as a precaution, but if you haven’t had trouble with corrosion, next time I take it out I may just give it a quick wipe down and put it back in the safe. Their website does say that the mealonite coating protects against corrosive primers, so I’ve never been too worried about it anyway.

  • dan

    I have the spikes upper and its awesome. Ballistic advantage are ones who produced the bolts and barrels for spikes. They have complete uppers , barrels , and bolts on their website. Another thing to note is the carrier is the same as m16, and the spikes/BA uses a standard firing pin. Dont know about the extractor though.

  • Jess

    My dedicated 5.45 AA piston upper had issues at first. #1 was an out of spec bolt that they apparently had a run of. I had to send it back for fitting as the replacement they sent me wouldn’t fit at all either. After that, it’s run 100% as long as the ammo feeds.
    #2 problem has been magazines. Even dedicated 5.45 magazines sometimes have issues. I bought 15 various 5.45 mags and 2-3 of them are either outright bad or unpredictable. The rest run fine, if being a bear to load. DON’T try to use a LULA. I haven’t tried the modified pmag yet, but that’s definitely on the list.

  • echelon

    I use AA piston uppers for all my ARs. The system is easy to clean, reliable and very lightweight. I really like ’em. Sorry to shill..

    As far as the ammo goes, while the 7N6 may dry up there’s still plenty of bulk 5.45 to be had for around $.21-.23/rd out there so it’s still cheap compared to most .223/5.56…

  • Machinegunnertim

    I was really excited that they finally came out with a mid length. I had to build my own almost two years ago. We all need to keep causing a fuss over the ammo ban or nothing will get done about it. I refuse to adopt a defeatist attitude about it and continue to send out this letter to different organizations and state reps. I encourage everyone here to do the same. –

    The Bureau of Alcohol Tobacco and Firearms (BATF) has officially banned shipments of 5.45×39 surplus ammunition also known as 7n6. Upon inquires from importers the BATF stated that someone had manufactured a handgun in 5.45×39, thus making all steel core 5.45×39 armor piercing under the BATF’s definition. In fact, under the laws definition it cannot be labeled armor piercing & must not be allowed to be banned. The story is even fishier as we learn more. You can read about here-

    I’m still trying to understand why a certain type of ammunition is OK in rifles but if a pistol is made that fires that type of ammo, now the ammo needs to be banned? We should all be outraged about this!

    It is well known that ammunition on average is as pricey and scarce as it has ever been in American history.

    With such a bad situation, ammunition such as the 5.45×39 7n6 is one of the few saving graces that lets us shoot afford-ably. Banning it only makes a bad situation terribly worse!

    Please don’t shove this on the back burner simply because it is a foreign import item. It is so much more than that! It is a deliberate attack on our rights!

    I am writing this letter in hopes that you will do everything you can to stop BATF from usurping the laws of this country in order to ban an ammunition not because it is what they claim it is but simply because they do not want American citizens to posses it. No federal agency has the right to make the law up as they go. If we allow that to happen The United States of America will cease to exist as we knew it.


  • Mitch

    “The cleaning is certainly easier!”. Ummm… I know what you’re getting at, but this may not be the best way to wrap up a review that includes you throwing the whole thing in this sink. A little CLP wipe down, some Mobile 1 synthetic, and a bore snake are all I’ve ever needed for my DI’s. As an aside- when corrosive is run through AK’s, does the user have to go through the same rigorous process to avoid rusting?

  • erwos

    “Cam wear-in” is very common, and works pretty much like you saw… a hundred rounds and done. I’m not saying “expect it”, per se, but it’s not a surprise to see.

    I’ve got the carbine version, and I’m very happy with it.

  • Not sure I see the attraction of trading mildly lubricious and easily scraped away carbon deposits for aluminum shavings in and on my moving parts group, and carrier tilt.

    • Mack

      i had the same problem with it wearing the upper receiver on both my piston guns, but not nearly as bad. but both got to a point and never wore anymore after that, same with the carrier tilt, on one of my guns it just wore through the finish then stopped on the other i put a POF buffer tube on it and i never had a single problem, if i new how to add pictures i would to back up my statment i would. if you tell me how to add photos i will gladly will. (One is the AA piston kit, other is Adcor Defense Elite)

      • Upload the images to Imgur or another image sharing website, and paste them into your comment.

        It’s not surprising that the wear would stop at some point. However, that does not speak well of the design at all.

        Why fix what’s not broken, especially when your fix goons up your receiver like that?

        • Mack

          These photos are from my Adcor upper, it stopped wearing at this point, but this was my first piston upper and i was concerned so i emailed Adcor and they sent me a box to inspect it and they said nothing was off but since i bought my upper they upgraded BCG and they upgraded me to that one. It didn’t wear anymore with the new one either.

          If i remember tomorrow i will snap some pictures of my AA upper, that one has the POF anti tilt tube on it and has virtually zero wear the last time i looked at it. the reason i got pics for the Adcor is because of the previously mentioned warranty claim.

          I 100% agree with don’t fix what is not broken, but i am all for an improvement. If everybody lived with don’t fix whats not broken we would all still be driving around Model T’s. I think its is an improvement for cleaning alone. They are practically spot less in the upper. I have never torture tested either one of them but they have never had a hiccup. Thats just my two cents.

          • I dispute the contention that piston ARs are an improvement, I guess.

  • Seth Martin

    How many rounds were shot for this review? I see something about 750 rounds and other places that say 50 and 100 more. Good review, it’s a shame the ATF couldn’t bear to see us have decent ammo on the cheap. What next? They’ll go after my surplus 7.62x54R?

  • n0truscotsman

    Sadly, this is not even as economical as it was before the ban. Steel case 223 and 5.56 has dropped considerably (as has 5.56 in general, even brass), which is why Ive been shooting my ARs more.

    This is one of those rare instances where *perhaps* gas pistons have more of an advantage than internal pistons: soviet surplus ammunition. Although this is merely speculation on my part, as I have not partaken in the combloc AR15 conversion bread yet.

    Indeed, it couldn’t have come at a worse time. Rather unfortunate.

    Ill tell you one thing too: well never see reliable 5.45 AR magazines or tavor conversions. Ever.

  • M38Mosin

    while steel core 5.45X39 may be banned from importation, there are lots of foreign and domestic mfgs, that make non-steel-core 5.45X39.