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Eagle Eye Brass vs. Lapua Brass

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This is a shortened version of a longer report. The longer report is not yet posted online, but includes more in depth statistical analysis. When that report is posted, this will be updated with a link.

I’ve used Lapua brass right out of the box for a number of years. It’s good brass. You don’t have to take my word for it; Lapua brass has a great reputation amongst competition shooters from many disciplines. It is the default brass used by the US Rifle Team and many other top tier groups of shooters. It is consistent and it offers many reloads before needing to be retired. It is for this reason that I recently compared Eagle Eye brass with Lapua to see how the new company’s brass would stack up. The long story short is that I spent many hours of my Christmas break measuring brass, carefully loading cartridges, on the range, and then sat back in a little surprise at the results.

Part 1 – Visual Inspection and Lots of Measurements

I had 100 pieces each of Lapua and Eagle Eye brass for this comparison. Each came out of a single box, each from a single lot. After visual inspection of the brass I noted that a large number of the Eagle Eye brass had what looked like little burs in the flash holes. The burs where not very thick and they were always on the case side of the flash hole, never on the primer pocket side. I took some pictures of the worst one and placed them at the link below. The Lapua cases did not have any of these non-uniformities in the flash holes.

Photos of Visual Inspection

Further visual inspection was pretty subjective, but I made the following observations:

The Eagle Eye cases had an orange tint on the inside, Justin Brown of Eagle Eye said this was due to a particular type of wash used for the brass. I thought the Lapua brass looked a little nicer, but that is a very subjective comment as it is based on appearances only. Others have had the opposite opinion, that the Eagle Eye brass generally looked nicer; that’s very subjective.

All 100 cases were measured for weight and length. In both cases, the average of three measurements was recorded. Most noteworthy are the extreme spread and standard deviations observed. With regards to weight Eagle Eye brass had a standard deviation of .240 grains whereas Lapua had a standard deviation of .754 grains. It is highly significant and surprising that the Lapua standard deviation on weight was 3x larger than with Eagle Eye.

Table 1 – Brass Weight & Length

  Eagle Eye Lapua
Weight (Grains) Mean 167.644 173.807
Std. Dev. 0.240 0.754
Range 1.000 2.700
Length (Inches) Mean 2.0038 2.0079
Std. Dev. 0.0006 0.001
Range 0.003 0.004

 

Part 2 – Loading the Ammo and More Measurements

Using a single jug of Hodgdon Varget powder, a single box of Sierra 2156 155 grain projectiles, and a single box of Federal GM210M primers I got everything ready to build some ammunition. The RCBS Charge Master was used to weigh powder and a Forster CoAx press with Forster dies was used. The un-exciting step which I’ve skipped was sizing the brass, that was done with the above setup and then the brass was tumbled for 10 hours to remove sizing lubricant. After sizing cases grew in length by about .001” (not all were measured after sizing, just a few to get an idea of what was happening). After loading the ammunition, each loaded cartridge was again weighed. The mean weights differed by almost the same amount as the difference in mean case weight (I.e., the powder charge and difference in bullet weight did not add much additional variation) as shown in Table 2. After visual inspection of the loaded cartridges I noted that the lack of chamfer on the inside edge of the Eagle Eye brass had led to small pieces of the bullet’s copper jacket being scraped up when the bullets was seated. An example photo is at the visual inspection photos link above. The Lapua brass already had a slight chamfer so this was isolated to the Eagle Eye brass. I speculate that this observation is confined to the sample of brass I received as I have not observed this with any loaded Eagle Eye ammo. It is possible that the brass I received was removed from the production line prior to the step where the chamfer is applied.

Part 3 – Velocity Measurements

At the range, the ammunition was fired 10 rounds at a time first with 10 rounds Eagle Eye, then 10 rounds Lapua followed by a time for the rifle to cool down. This was repeated until all 200 rounds had been fired, each time alternating which brand went first. The 10 shot groups fired varied in sized from approximately .75 MOA up to 1.5 MOA. In many cases, the first three to six rounds fired would go into one ragged hole before the remaining rounds would increase the group size. Consistency of aiming point (mostly affected by mirage off of the barrel) and other environmental factors are assumed to be responsible for the larger group sizes. The ammunition was fired in the same order that the loaded cartridges were weighed so that any relationship between cartridge weight and muzzle velocity could be observed. The mean velocity for Eagle Eye was 3004 fps and the mean velocity of Lapua was 3020 fps. The difference in mean velocity with the same load is speculated to be the result of differing internal case volume which lead to differing load pressure resulting in differing velocity for the same load. The table below summarizes these measurements. It is noteworthy that some statistics gymnastics revealed a correlation between loaded cartridge weight and velocity for the Lapua ammo but not for the EE ammo. My palma rifle was used for this testing; it has a 30” barrel with a 1:13 twist and was shot from a bipod with a scope over a chronograph which was 10 feet from the muzzle. Analysis of the data in Table 2 showed that the difference in standard deviation was statistically significant. Also, note the interquartile range (IQR) difference between the Eagle Eye and Lapua.

Table 2 – Cartridge Weight & Muzzle Velocity

  Eagle Eye Lapua
Weight (Grains) Mean 374.85 381.16
Std. Dev. 0.271 0.750
Range 1.200 2.700
Velocity (Feet Per Second) Mean 3003.96 3019.95
Std. Dev. 10.750 13.017
Range 50 51
IQR 13 21

Part 4 – Conclusion

Lapua brass was used as the benchmark by which the new Eagle Eye brass could be compared. Close visual inspection showed the Eagle Eye brass could be refined in some areas in order to be as presentable as the Lapua (E.g., flash hole uniformity, chamfer on case mouth, etc.). Measurements of weight and length showed that the Eagle Eye brass was more consistent than the Lapua brass. Velocity measurements showed a correlation between overall weight and velocity with Lapua cased ammo, but not with Eagle Eye cased ammo. This could mean that some of the variation in weight with Lapua brass is also responsible for altering the internal volume of the case, thus changing the load’s pressure and ultimately the projectile’s velocity. Overall, I was pleasantly surprised by what I measured in the Eagle Eye brass. Out of the box, with no modifications other than re-sizing (which was done to both Eagle Eye and Lapua brass), the Eagle Eye brass created a round that was significantly more consistent than my typical competition load.

 

For more information about Eagle Eye Ammo and its current offering of match ammunition please visit Eagle Eye here: http://eagleeyeammo.com/.   Note that the Eagle Eye brass tested is not yet available for purchase, but it is the same brass used in their loaded ammunition.

Aero Precision AR-15 Continuous Optics Platform (COP) Kit

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Without having an extra barrel to mount up this first review will be a little brief and will focus on the kit and my initial impressions.  The kit comes rolled up in a canvas pouch with everything needed to customize the kit into a number of various configurations.  Rolling open the kit reminded me of the many action movie scenes I’ve seen when someone rolls out their super compact tool roll-up to reveal the knives, lock picks, etc. that were needed.  I realize it’s just a canvas roll-up, and maybe I’m easily impressed sometimes, but I like it.  The upper is very solidly built and exudes quality.

In order to get a somewhat measureable idea of the machined tolerances I took apart my home defense AR and snapped the COP upper on.  It was a very tight fit, perhaps the tightest fitting upper I’ve ever snapped onto a lower.  After a few light taps into place the upper snapped in just fine and because of the tight tolerances showed absolutely no perceivable wiggle or slop with the lower receiver I had mated it with.  I take this as a very good sign of things to come and while it was a little tight on assembly, the tightness of fit should lead to more reliable feeding and even increased accuracy when I add a barrel and optic to this upper.

In the kit come the Torx wrench needed for final assembly as well as a special barrel wrench that is needed because of the monolithic upper/forend configuration.  The barrel wrench looks to be of high quality, more like something that you’d find in a gunsmith’s tool box and much less like the one time use tools that come in some kits I’ve seen.  I mentioned the COP kit offered customization and that primarily comes from the ability to add any of three different rails to each side of the kit.  The rails included are each 8.25” (or about 21 cm) in length.  The full length Picatinny rail inserts have laser engraved T-markings starting at 18 and going to 36.  Two of the Picatinny rail inserts have sling a sling socket at each end.  There are three combination Picatinny/smooth rail inserts.  A little over half of these inserts is smooth for better gripping the rifle and the last portion is Picatinny rails; one of these combination inserts has a sling socket built in.  The last three inserts are smooth for the whole length and in my estimation would decrease the overall thickness of the forend section by 0.5” or more.  The smooth sided inserts would make sense for someone who will only mount optics on the top rail and needs as much of the forend for grip as possible.  One of the smooth inserts has a sling socket built in.

I look forward to building this AR-15 COP Upper Kit into a complete upper and taking it to the range.  Thus far I can definitively say that the COP Kit is unique in its design with the interchangeable forend inserts and I think that the added rigidity of the monolithic upper/forend system is an exciting addition to the AR-15 platform.

Thank you to Aero Precision for providing the COP Kit for review.  For more info on Aero Precision products check out their site: AeroPrecisionUSA.com.  I will likely be carrying much of the Aero Precision line of products in the near future.  Please stay tuned!

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