Studies showing piston Ar's more reliable?

[lysander]

This is just another piece of terminology used on the AR system that is used incorrectly.

Dwell time - Everywhere except the AR world, dwell time is the time from primer ignition to bolt unlocking.
Direct impingement - Every where else this is an expanding gas system.

There will probably be more in the future.

[juliet9]

You might think that . . . but, the new builds account for 64% of the Class III malfunctions, while the rebuilds account for 99% of the Class I/II stoppages.

Here are the results from the EPM (blue follower) tests, 9 M4A1s, 3 new, 3 PIP, and 3 rebuilds, and 6 M27s, all shooting 6,000 rounds each:

New - 6 Class I/II, 3 Class III
PIP - 15 Class I/II, 4 Class III*
Rebuilds - 2 Class I/II, 4 Class III
M27 (M855A1) - 14 Class I/II, 0 Class III**
M27 (M318) - 2 Class I/II, 1 Class III

The initial MR firing dispersion of the new and rebuilt weapons was pretty much the same: New - 3.1", Rebuilt - 3.6"
______
* 10 of the Class I/IIs are from a single weapon
** evenly spread across all three weapons

Are we to assume that the M27 tally are "new" weapons? The original test stats outlined in your first post seems to be skewed all the way around with different condition M4 types versus presumably "new" M27 types. Add different round counts (original test) to the equation and it seems to me with a cursory review that the test is favored to the M27.

The same holds true with the "blue follower" test save for the constant round count, as rifle condition comes into play.

From my experience, and to obtain accurate results, controls should be in place i.e. both round count and rifle condition.