Originally Posted by sunofnun
There are two major types of centerfire rifle cartridges available on the market today:
Those which are loaded with steel, and
Those which are loaded with brass
This seemingly simple variation has caused a never ending stream of argument, discussion, speculation, and questioning from new and seasoned shooters alike. Complicating the conversation are other variables that typically get lumped into the argument without proper segmentation, such as:
The different coating options available on the steel-cased ammo (lacquer or polymer)
The different projectile loadings available (copper jacketed lead, the bi-metal coating that most Russian manufacturers use, etc)
The different propellant (gunpowder) burn rates
Our team decided to try something ambitious and daunting: to provide the best resource and data available to answer these questions once and for all through objective experimentation and observation.
We realize this is a lofty and borderline arrogant goal. We’ve done our best. Please keep reading to see if you agree.
Here’s what we did:
We acquired four identical Bushmaster AR-15 rifles. We chose the Bushmaster MOE Series AR-15 because it’s a widely available, affordable, and mass-market. We didn’t want something too cheap and of lower quality or something too expensive and of high quality since our goal is to help the most number of people.
We acquired 10,000 rounds each of the following ammunition (new production):
Federal 55gr – Brass-Cased – Copper Jacket
Wolf 55gr FMJ – Steel-Cased with Polymer Coating – Bi-Metal Jacket (steel and copper)
Tula 55gr FMJ – Steel-Cased with Polymer Coating – Bi-Metal Jacket (steel and copper)
Brown Bear 55gr FMJ – Steel-Cased with Lacquer Coating – Bi-Metal Jacket (steel and copper)
We paired each ammunition type with a specific Bushmaster AR-15 and then fired all 10,000 rounds of it through that particular carbine (except for Tula; more on that below)
We systematically observed and tested various things, including (more details below):
At the start: accuracy, velocity, chamber and gas port pressures, chamber cast
After 2,000 rounds: accuracy, velocity
After 4,000 rounds: accuracy, velocity
After 5,000 rounds: throat erosion, chamber cast
After 6,000 rounds: accuracy, velocity
After 8,000 rounds: accuracy, velocity
After 10,000 rounds: accuracy, velocity, chamber and gas port pressures, throat erosion, extractor wear, chamber cast, barrel wear
We logged every malfunction of every rifle-ammo combination
The rifles were cleaned according to a preset schedule and temperatures were monitored and kept within acceptable limits (more below)
We sectioned the barrels and otherwise made unique observations after the test was complete
If you’re interested in any of the following, you’ll find observations, data, and further details below:
Which ammunition was most reliable?
Which ammunition was the dirtiest?
Which performed better, lacquer or polymer coating?
Which ammunition maintained the highest degree of accuracy throughout the test?
Which ammunition maintained the most consistent velocity throughout the test?
Which ammunition caused the most throat, barrel, and extractor erosion/wear?
What effect did the powder burn rates have on bolt cycling?
How did the pressure at the gas port vary by ammunition type?
How did the pressure at the chamber vary by ammunition type?
Which is cheaper to use, after considering all the costs?[/url]