Does Nickel Boron Reduce Heat?
We've been bombarded with a variety of coatings and platings over the past few years, most of which are called "proprietary" and given a cool name. In reality, there aren't a whole lot of finishes or metal treatments out there. Many are just variations on a theme, such as all the derivatives of nitrocarburization and nickel plating.
Nickel boron is related to electroless nickel plating and electroless nickel with teflon (also known as Robar's NP3) with regard to the plating process. Nickel boron is reported to provide "permanent dry lubricity". In other words, less friction amongst the reciprocating parts, as well as where they interface with static components.
It didn't really occur to me that this might lead to lower operating temperatures. In fact, when I noticed a discrepancy between a rifle with a nickel boron BCG and a similar rifle with a standard, phosphate finished BCG, I wasn't sure what to think. They used different rail systems and gas system lengths. Initially, I chalked it up to those minor differences. Then, I decided to use a standard BCG in the rifle that was originally equipped with the NiB BCG, using the same test protocol. After that, I repeated the test, twice, with each BCG, allowing the weapon to cool to ambient temperature between strings of fire.
The test was performed by firing 80 rounds of centerfire ammunition as quickly as possible through the AR-15 pictured below:
No malfunctions were experienced during any of the 5 strings of fire.
I then measured the temperature of the gas block, chamber, bolt face, and handguard (in four locations) immediately after firing and at two minute intervals out to 10 minutes.
For the sake of comparison, I have included the temperature of an M4 type carbine equipped with a KAC M4 RAS handguard. The rifle above was equipped with a Daniel Defense OmegaX 9.0. None of the rails had any covers during the testing.
Gas block temperature profiles were nearly identical for all weapons.
The same goes for chamber temperatures.
Bolt face temperatures, however, were another story.
The bolt face of the nickel boron plated BCG stayed, at its peak, 13 degrees cooler than the same weapon with the standard BCG, and 17 degrees cooler than the M4 carbine with the KAC M4 RAS.
Here is the nickel boron BCG compared with the POF RDIK and POF P-415 uppers, which underwent the same test (again, we're talking bolt face temp here):
As always, I'm not a scientist and this was not a scientific test, but I do feel fairly confident in the results, given that I double and triple-checked the numbers and nothing was outside of a small margin of error. The above numbers are the average of said tests and retests.
I do realize that this was a sample size of one and that the limited testing doesn't definitively prove anything. I do think that it is an interesting result that I would like to follow up on after I get more ammo and possibly more nickel boron plated BCGs.
Heat Dissipation: Insulate or Circulate? Gas Tube or Op-Rod?
Standard disclaimer: I'm not a scientist and this was not a scientific test. Any conjecture on my part is purely an uneducated guess.
As I've written before, POF-USA provided me with two of their upper receivers - one is of their standard P-415 design and the other is actually operated via a standard gas tube. It's called the RDIK.
This gave me the opportunity to compare how each handled heat. That is, just how effective are all the design changes POF has made to the AR receiver, barrel nut, and handguard? Well, as I found out, they're quite effective. However, that test was pretty limited - only 30 rounds per weapon - and I wanted to step it up a little.
Today I put 80 rounds through each of three ARs - the P-415, the POF RDIK, and an M4 type AR with double heat shield handguards - and will shoot more in the next few days with other weapons. I also took chamber and bolt face temperature readings, in addition to the handguard temp (average of 4 places on the handguards) and gas block/barrel temp.
The rounds were fired as quickly as possible, and the rifles were left with the bolt carrier group in the forward and locked position. Temperature readings were taken immediately after firing and at two minute intervals thereafter, out to 12 minutes post fire.
We'll start with handguard temperature.
As you can see, the M4's double heat shield handguards were much hotter than either POF offering. The POF RDIK, in fact, had a slightly cooler handguard than the POF P-415.
This was in part due to the very hot gas block of the P-415. Here are those temperatures:
It wasn't quite as scorching as the M4's 353 degrees immediately after shooting, but it was over 320. The POF RDIK was drastically cooler - it never exceeded 200 degrees.
Chamber temperatures were much closer for all weapons.
The P-415 did stay cooler than the RDIK, with a difference of roughly 10 degrees. The M4 was hotter than either of the POF weapons, due in no small part to the heat sink barrel nut used on the POF rifles.
The following graph shows bolt face temperature.
It would appear that a large portion of the heat reaching the standard AR-15's bolt comes from the front - that is, the chamber. If we compare chamber and bolt temperatures, the RDIK and M4 hardly ever had more than a 2 degree difference between the chamber and the bolt (with the bolt normally being 1-2 degrees cooler than the chamber). The P-415 bolt, on the other hand, generally stayed about 10 degrees cooler than the chamber.
What does this all mean? Well, to me, it means that getting the heat out (circulating air) is more important than trying to keep the handguards cooler (insulating the barrel with double heat shields) - regardless of the operating system you choose. It would appear that the piston/op-rod P-415 does slightly reduce bolt face temperature - but the RDIK does a very fine job of keeping the chamber area cool in its own right, which in turn keeps the bolt cooler.
It seems that there is no free lunch, and the heat which is not present in the P-415 chamber and bolt is very present at the gas block. The heat sink features and wide open handguard with lots of cooling slots almost seem necessary to keep the barrel/gas block temperature relatively in line with that of the M4 type AR. I would really like to test an op-rod conversion that does not have the heat sink barrel nut, big handguard, etc.
I would assume, based on these graphs and the comparison of the three uppers, that the large majority of the temperature of an AR-15 bolt during sustained fire can be attributed to the "fire in the barrel", and a minority comes from the gas which circulates through the action. In other words, with the piston/op-rod system, the chamber "heats" the bolt, whereas in the standard operating system, the bolt is heated not only by the chamber but in a small way by the gas coming through the gas key, which in turn causes the bolt to pass some heat back to the chamber. As a result, the temperature of the bolt and chamber on a standard AR are married to one another to a greater degree (ha, ha) than on the P-415.
Again, I'm not a scientist. If anyone has a better conclusion based on the above data, I'm all ears.
Spike’s Tactical Midlength LE Upper Receiver Assembly
Some people are in the market for a new AR or AR upper.
Some people don't think they're in the market until something special catches their eye.
This could be a part that has special features, or a good product at a good price.
Or, for that matter, something that has special features and is at a good price.
The Spike's Tactical LE uppers are certainly in this last category. They're under $500, shipped, with a $50 coupon code - M4LEUP for the M4 type upper ($475 with the code), or MIDLEUP for the midlength upper ($485 with the code).
There are budget uppers available in the $300 range, but they lack many of the components - and nearly all of the features - of the Spike's uppers.
For example, a $275-300 upper without a bolt carrier group, charging handle, or possibly handguards suddenly becomes a ~$450-475 upper. How much was the Spike's M4 LE upper again? Oh, right. $475.
Thus, it is with bewilderment that I observe people who buy said cheap uppers. When reports of mismatched receivers and barrel extensions, missing gas ports, barrel extensions coming loose, etc surface, I am not very surprised.
Perhaps it's inappropriate for me to divulge information that was learned in a private conversation, but I don't think Tom Miller, CEO of Spike's Tactical, would mind very much. 6 or 8 months ago, we were emailing back and forth about new products. When the subject of a company "goal" or "mission" came up, Mr. Miller essentially said that he wanted Spike's Tactical to be regarded as one of the best AR-15 manufacturers in the business. That's a lofty goal, but it's one that they're well on their way to achieving, if the uppers I've seen are any indication.
Keep in mind, there was no price "string" attached to that goal. He didn't say "we want to be the best budget manufacturer in the business" or "we want people to say we're the best because we're cheap".
I learned everything I needed to know about Tom and Spike's Tactical from that one statement.
So, after that long-winded diatribe, back to the subject at hand: the ST Midlength LE upper assembly.
This particular upper came with a few extras, as you can see. Excellent extras, I should add - a Smith Vortex flash suppressor, a Daniel Defense OmegaX 9.0 rail, a Daniel Defense A1.5 fixed rear sight, and a Bravo Company MFG Gunfighter Mod 4 charging handle, among others.
All Spike's uppers are marked with their logo. They might be able to assemble an upper sans logos for those who prefer a blank slate - don't quote me on that. Here you can also see the DD rear sight and the excellent BCM charging handle. Now that I think about it, the DD rear sight is excellent, too. It's so light that it actually reduces the weight of your rifle when you attach it...
Another nice option for ST uppers is the Nickel Boron bolt carrier group. Nickel Boron provides corrosion resistance as well as a good amount of inherent lubricity. The Spike's Tactical nickel boron BCGs are done by FailZero, but with a little more attention to detail (such as carrier key staking and extractor/bolt quality).
Also, they offer laser engraved ejection port covers. I think they should offer one with the spider logo that also says "Surprise, Small Insects!" Sadly, they do not. By the way, the American flag is not backwards - the field (portion with the stars) is always oriented towards battle. Were the flag to be displayed in the traditional manner on the right side of the weapon, it would be "retreating."
Evidence of test firing is plainly seen on the brass deflector. This is definitely a good thing.
An F height FSB. Taper pins that are properly driven in. These are items that some other manufacturers in the price range ignore.
M4 feedramps on both the barrel extension and the upper receiver are standard on all Spike's uppers. This set isn't an absolutely perfect match, but I do not foresee any issues from this particular combination.
The entire BCG - except for the firing pin retaining pin and extractor pin - are Nickel Boron plated. Because electroless nickel plating is strongly influenced by surface preparation, and because this BCG is incredibly smooth to the touch, I'm inclined to believe that every surface was polished prior to plating. Either that, or Nickel Boron has, literally, magic properties. Either way, friction should be greatly reduced.
As expected, the bolt also showed evidence of test firing. One benefit of nickel boron is that cleaning is much easier. Everything you see here wiped off with hardly any effort.
The extractor spring used is an "extra power" spring, and is identified as such by the black insert, and the o-ring provides additional extraction force. For some applications, this may be unnecessary. Still, it's nice to have it included.
This concludes my brief overview of the basic features. More to follow...soon.
5/6/10:
I didn't shoot any groups today, but I was pleasantly surprised to find that the iron sights had already been zeroed, and the rounds were going where I intended them to go.
The Nickel Boron trigger, hammer, and disconnector also added up to a very manageable and clean trigger pull. I will definitely be purchasing several of the Spike's LPKs to replace standard GI triggers in a few of my lowers, including my other Spike's lower.
And, finally, after shooting several ARs that are not so equipped, using the BCM Gunfighter charging handle was akin to returning from a long days' work to find a home cooked meal on the table.* It's just that good.
*In deference to all the empowered women out there, we are going to assume that said home cooked meal simply appeared on the table, as if by magic.