What these guys did was preform a controlled torture test on 4 identical AR-15's with 4 different types of ammo. The test was quite amazing and the results were quantified in a scientific and very useful manner.
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.Obviously the report is much longer. If you are an AR guy and you buy ammo, please take a look at this report. They did great work and I think you'll find the information they complied very useful. If anyone has contact with Professor Hale, please send him this, its right up his alley.