“A million shots from one mag” - dodgy tests?

[SSPKali]

Been thinking about this for a while and would open it up to the hive mind to see if I am on to something or talking cross-eyed badger spit.

There are plenty of videos out there where someone fills a mag with gas, but no BBs, and proceed to fire until the bolt or slide won’t lock back. They then proclaim that “tHiS GnU iZ ThE bEsTs bCuZ tWeLfTy tHoUsAnD sHoTs oN oNe MaG”

But here is the rub, there is no BB being fired and thus less gas used. Usually the pressure in the barrel due to the BB blocking it keeps the rocket valve open. Once the BB leaves the barrel and the pressure drops the rocket valve can close against the little spring. This diverts the gas back and cycles the action.

So are these tests misguided and a rough guide only? 

 

[Adolf Hamster]

sort of yes and sort of no.

whilst yes a bb will be using gas for its propulsion, if you consider the effeciency of nbb platforms versus blowbacks it's evident that the lions share of gas usage in the gbb is in actually cycling the thing, and tests with no bb fired do still demonstrate that the relevant sealing surfaces are doing a decent job of not sending half the reservoir into the atmosphere every shot.

that said, an element that firing a bb will bring to the table is an increase in backpressure, one thing i found running heavier than your average ammo in pistols is that one side effect is the bulging (and i've heard albeit only anecdotally catastrophic bursting) of the nozzle due to the pressure, needless to say, this is gonna be putting more strain on the sealing surfaces which wouldn't be there in a dry fire test.

 

[SSPKali]

Thanks, not owned / used a NBB for comparison - I know anecdotally they are more efficient in terms of shots per mag fill.

If I get really bored one day I might give it a try both ways and compare.