Recently I was sent an upper receiver by Spike’s Tactical for test and evaluation. In the interests of fairness, this upper was provided to me for free. I still approached it from a critical angle and tried to find problems with the upper – of which there were none to find, making my job a little harder.
If you’re familiar with Rob Sloyer’s infamous “Chart” detailing what makes a good fighting carbine, well, this upper checks every box but one. The bolt is not HPT’d, also known as “proof tested.” Proof testing is where a special high pressure round is fired, making flaws or cracks more obvious during subsequent magnetic particle testing.
Beyond that, every specification equals or surpasses “mil-spec.” We see that word thrown around a lot, and it’s both good and bad. When it comes to the M4, generally, a mil-spec item is a good one. There are improvements that can be made – say, a 5 or 6 position stock instead of a 4 position, as long as the replacement is of equal quality – but if you were to be in the middle of a firefight with a mil-spec Colt M4, you would be well equipped.
So, what do I mean by “surpassing mil-spec” with regard to this upper? Well, the barrel is hammer forged. What is hammer forging? Essentially, a larger-than-normal barrel blank is placed over a mirror image of the rifling; the barrel is then hammered into shape. I’ll leave the technical info to the metallurgists, but real world reports from high-volume shooters indicate longer barrel life.
Upper Receiver Teardown
I’m of the opinion that the barrel and the bolt are the heart of any AR-15, and a quality example of each will lead to excellent reliability. This upper has essentially the best barrel you can purchase for the AR-15 – hammer forged by Daniel Defense in Georgia.
The bolt is also top-notch and includes a strong extractor spring with an o-ring.
The bolt carrier is properly staked, and marked by Spike’s Tactical with their logo.
The upper receiver had M4 feed ramps machined prior to anodizing, and the barrel extension matches them perfectly. You can see the excellent job that was done by whoever did the chrome lining in this picture. Sometimes, barrels have uneven chrome lining “shadows” at either end – that won’t really affect anything, since the bore and chamber are the important parts, but attention to detail always impresses me.
Why have M4 feed ramps? Well, the military found them to be necessary with this gas system length and in sub zero temperatures. I’ve also found them to be helpful in the case of magazines that may not hold the top round at the proper angle, resulting in failures to feed in non-ramped uppers.
In this photo, you can see parkerizing under the front sight base, which also happens to be the proper height for the upper receiver and gas system length, and is marked as such. Why is parkerizing under the FSB important? Well, I’ve had non-parkerized barrels rust even in this dry Arizona climate, making FSB removal very difficult. It won’t affect function, but it’s something that I like to see on my rifles, because I change things around from time to time.
Here’s the gas port. Why do I mention the gas port? Well, this is where gases from the fired case come out of the barrel and into the gas tube. Some civilian manufacturers make their gas ports too large, in order to maintain functionality with weak, underpowered ammo.
Unfortunately, because the gas port erodes over time, this means that the overall life of the barrel is shortened, and too much gas goes back into the action from the very first round on. It’s like buying new tires that have half the original tread depth. This gas port is a good size, .068, and the rifle functions with all ammo. Sometimes you’ll see gas ports above .1″, and in extreme cases, over .2″. Steer clear of these barrels.
Also included with the upper is the Spike’s Tactical ST-T2 buffer, which is an excellent upgrade for any rifle, as I’ve found. It’s heavier than standard and H buffers, and does reduce felt recoil. The added weight also helps maintain proper functioning.
Since receiving the upper, I’ve fired a wide variety of ammunition through it in an attempt to make it malfunction. I’ve fired everything from military M855 to handloads specifically loaded to be almost impossible to extract by hand. The extra power extractor spring and o-ring, however, prevent the extractor from slipping off the rim of the case, and I’ve yet to have a single malfunction with the upper. I even hand the rifle off to random folks at the range, who’ve shot mags full of their own Wolf and other steel case ammo, Ultramax factory reloads, etc. Its reliability is very impressive.
Firing handloaded 73gr Berger HPBT bullets in Lake City cases, using Varget powder, I fired this ten shot group, which measured 1.45″. That’s more than adequate from a non-free floated carbine barrel. Often we see three or five shot groups bandied about, especially in magazines – the only problem is, if you laid three of those three shot groups on top of one another, they’d probably triple in size. I like firing ten shot groups, because after ten shots, your group size won’t increase much more, if at all. Therefore, ten shot groups are a good indicator of the maximum spread you could expect from a barrel.
Eagle eyed readers with five fingers on each hand will spot only 9 holes – 10 were fired and 10 impacted the paper. None are hiding under the calipers.
In summary, I can’t think of any changes I would make to this upper. I prefer midlength gas systems, but a carbine length gives you more options if you want to shorten the barrel in the future. The build quality, accuracy, and reliability of this upper are second to none.