What causes first round pop?

[MuzzleFlash]

I've heard this term a lot but never found an explanation for what causes it.

 

[stymie]

Oxygen or a combustible liquid/powder...

will ignite/detonate when a round is fired, causing 1st rd pop!

Cleaning out unburnt powder residue & avoiding flammable ablative mediums in *wet* cans helps somewhat.

Some of the more exotic baffle designs will effectively contain this phenomenon & slowly release the resultant sound pressure.

Introducing carbon dioxide into the suppressor system will usually prevent this from even being an issue.

In Vietnam, operators equipped w/ the SIONICS MAW-A1 would *blow* into the WerBell valve to charge the unit.

 

[chrisp929]

funny you say that sty .. about blowing into the can .. as i was reading muzzle flashes question .. the blowing into the can came to mind ..

 

[Renegade]

Oxygen and a lack of heat in the silencer. Both of which are overcome when a few rounds have been fired through it.

 

[Racer]

First round pop is caused when the superheated carbon monoxide and the unburned particulates in the combustion gas combine with the oxygen in the suppressor to cause a secondary combustion in the suppressor itself. After several shots have been fired, most of the oxygen has been used up and the shots get quieter due to less of this secondary combustion. There are several ways to avoid or reduce FRP. One of the most common is to use a coolant in the suppressor (water, oil or grease) that vaporize with each shot and cool the combustion gases below their flash point. Another way is to remove all the oxygen from the suppressor before firing the shot by injecting non-combustion supporting gas into the suppressor e.g. CO2, or a third way is to design the baffles etc. to either cool the gas or contain the secondary combustion sound. Some suppressors are much better at containing the FRP than others.

 

[MuzzleFlash]

Great answers guys, thanks!

I bet dry ice crystals in the blast chamber would squelch things pretty good. Then again, they could bounce around and damage baffles before turning into gas.

 

[stymie]

A CO2 cartridge/powerlet...

could be valved into the expansion chamber for effect.

....um, nevermind