Chronoing Gas Shotguns

[CamboL]

Hi All,

Tried to search but couldn't find a topic on this

Recently picked up a Gas M870 shottie that shoots in either 3 or 6 shots

When I chronoed at home was putting out 5J on green gas on 3 shot - I've tried then to chrono with just 1 bb which was still showing 2.5j until I moved slightly further back (2-3inches - oooh errrr) from the chrono - then was getting 1J. I assume this was the unspent gas also exiting the muzzle and entering the chrono - skewing the data.

My question: How do most sites chrono shotguns on the day? Want to try out my new toy - but dont want to be hit with a silly 20m MED because the chrono isn't reading right

Cheers!

 

[Austeyr]

The majority of the sites I’ve used a shotgun at have asked to load one bb into a few shells and chrono that way, not sure if that’s the norm but to me it’s the most logical 

 

[LMKipper]

Chronoing gas shotguns is both easy and hard, depending on the kit on hand. As you've found, most site chronos struggle - the gas can upset them, as can multiple BBs going through the gates, which is how you end up with mad 5J readings.

Lots of places will tell you to just load one BB and fire that, which is inaccurate the other way and often leads to lower readings (lots of gas will just escape out of the other barrels). The only way to do it really accurately is to use radar chronos (https://airsoftdirect.uk.com/product/valken-airsoft-chronograph-custom-chrono-x-radar/) but they're not especially common.

FWIW if I chrono at home with multiple BBs, I often get 3J+ readings. If I chrono with one BB, it will usually show around 0.7J but if I chrono on a radar with three BBs it's around 1J. 

 

[Lyndication]

Load the shell normally, get close to the chrono, and put the barrel so that only the top inner barrel will actually fire through the chrono. The other two should just smash against the table or whatever. 

Yeah it sucks, but like the others said if you just fire three BBs through the chrono it gives bad readings, but also if you fire with only one barrel loaded the gas vents out the other two and the measured power on that one BB is much lower.

 

[Cannonfodder]

Most sites I've been to ask you to only load 1 bb and chrono that.

Load the shell normally, get close to the chrono, and put the barrel so that only the top inner barrel will actually fire through the chrono. The other two should just smash against the table or whatever. 

At Blackstone they put a piece wood in front of the chrono and did this. To me this is the most accurate method