Stock JG spring in a G&P mechbox. What velocities should i expect?

[theguy]

Title says it all.

I got a new G&P gun in December, and right away installed an s90 spring for safe indoor play.

This weekend, I am going back outside

I am thinking my s90 might leave me a little under power.

To choose from for other springs, I have the stock 1J G&P spring, or a stock spring from a JG G36c.

If i try the JG spring, Will it put me over 400? I think it was shooting about 375 in my JG, but that was with crappy compression parts, and no bearing on the spring guide/piston head.

I unfortunately don't own a chrono (its on the list)

Should I try the JG spring and hope it doesn't put me over 400? Or should i just stick the the ~300 fps spring i have now.

I would just order a new M100 spring, but the game is tomorrow.

Thanks,
Ben

[L473ncy]

Depending on if you live in the sticks or not (this will require a large outdoor space) there is another way you can get a fairly accurate idea of how fast you're shooting.

Setup 2 microphones a known distance apart (say 10 meters). One nearby you and the other 10 meters down range. Set them up to record sound (Audacity a free piece of software and is good enough, in fact people seem to use audacity a lot for this test) and shoot down range. Now in your audacity recording you'll see two "spikes" in sound (the other sound just being ambient sound) at different times, subtract these. The peaks are what you want to be looking at. Using some math-fu and physics formulae you can figure out how fast you're shooting because you've isolated the distance and time variables so just figure out your speed.

This is a lot more accurate than the "coke can" test (apparently aluminum is slightly different thickness depending on where you live and even between different batches/companies.

[theguy]

Hmm..

Okay, I will give that a shot this afternoon.

I am not sure if i Have 10m of space though, think the test would be as accurate in an area half that size?

[L473ncy]

Originally Posted by theguy

Hmm..

Okay, I will give that a shot this afternoon.

I am not sure if i Have 10m of space though, think the test would be as accurate in an area half that size?

I actually have no clue. It probably would be the same, since you haven't really changed anything, the distance is still known (in this case just being 5 metres).

What you want is just a formula to calculate right:

V=D/T

Velocity is what you're trying to solve, distance is known (5 meters) and time is also given as a result of calculating the difference in time that the BB passes each microphone in the shooting test. As the object passes the microphone, the microphone should pick up the "woosh" sound of the BB passing it. Since you have the distance AND both "T1" and "T2" take the difference in time as the object passes the measured out distance. Note that you want to negate the noise of the motor so pick the "peaks" where the BB is passing the microphone NOT the motor noise or a dog barking or anything else.

There's actually a website somewhere that documents this and how to do it. I think it may be on Arnies or something, just google it and you should be able to find it.

[Skladfin]

it would be more accurate with 5 metres, hell, even 2 metres.

BB loses velocity quite fast, that is why the more distance you give, the less accurate it is.

[theguy]

Alright, I am going to see if I can dig up a second mic anywhere and give this a shot.

I will report back if i can find one.