Blue vs clear bumper

[athomas]

Is this a vacuum pressure?

That question doesn't even make sense.



The bolt works much like a regulator. It has a piston (bolt stem) that is forced out by air pressure. There is a spring that pushes back against the bolt to limit the amount of air that gets out. On a level 10 bolt setup, the smaller stem allows less force against the bolt spring than a level 7 bolt, which is why the level 10 is easier on paint. Unfortunately, it also results in less air flow. Less air flow results in the chamber being dumped slower, especially as the pressure reaches the value equal to the spring return force. This is how a regulator works. Once the spring force is greater than the chamber force exerted on the larger part of the stem (since the bolt is now forward), the bolt is forced back to its reset position. Because the level 10 air is flowing at a reduced rate through the smaller carrier opening, the regulation is more precise and closer to the spring rating than the more quickly dumped level 7 air. This results in more air remaining in the chamber of a level 10 equiped valve, which slows the rate of the returning bolt.



The shredding of the clear bumper has nothing to do with the rate of acceleration of the bolt towards the back anyway. If the back to the level 7 bolt was machined to the same dimensions as the level 10 bolt, it too would tear the clear bumper. The clear bumper being softer squishes as the bolt is returned. The inner part of the bumper is tight against the valve stem and can't go anywhere. The inner edge of the bolt holds it from moving anywhere when the impact occurs. The remaining bumper material squeezes to the only place it can, which is towards the outside edge. The movement of the bumper material with the inner part held tight creates a tearing action on the material. Eventually it fails. The fix is to glue the bumper down. This prevents the migration of the bumper material towards the outer edge and prevents the tearing action and thus, saves the bumper. The blue bumper, which does not compress at the same rate, does not suffer from this affliction.

[garbageman705]

My E-mag has had a black bumper on it for like 5 years.

[PhoenixWolf]

I seem to recall that AGD later stated that it doesn't really matter (this was years later). They originally thought that they would need the softer bumper for use with higher performance guns. However, they underestimated the quality of their engineering, and underestimated how quickly these new bumpers would wear out. End result is that most people just use whatever they have on hand, and don't worry about which bumper they have. Given that people use the blue bumpers on E-Mags for years with no sign of wear, it's pretty obvious at this point that it doesn't matter.