SpudFiles

Hey Guys,

I have been doing a bit of velocity testing lately and I have a question for you (those who understand the math far better than I).

I have gotten some odd readings from my Chrony. The gun I am firing is a 1 and 1/4 inch (nearly 1 and 3/8 inch bore) barrel, 4 feet long with a 2 to 1 tank to barrel ratio. The gun uses a 1 and 1/4 inch brass Granzow diaphram valve pilotted with a 1/2 inch bore diaphram valve. It is a very fast acting valve with a good flow rate. Firing a 25 gram slug (hollow plastic bottle wrapped with black duct tape) at 210 psi, my Chrony recorded a 1,179 fps reading, the next shot showed only 162 fps. I know the 162 fps was incorrect. However, I am not sure the 1,179 fps reading was right either. Honestly, the recoil was freakin VIOLENT! HOLY COW! Also, the stop I was using (carboard box with a couple loose towels inside) could not stop the slug. It went right through. So, I know my velocity is high, but from a previous thread, it has become clear my Chrony numbers may be off a bit.

So, who can crunch some numbers for me on this?

Oh, by the way, this stuff is ADDICTING!

Matt

What model is your chrony, and how far away is it from the muzzle? Sometimes muzzle blast can interfere with the ready if it's too close.

Oh, and videos please!

Like jack said. Not only can the concussion affect a normally operating chrony it can really mess with one that has a bad solder joint, or wimpy battery connections, or ...

Gotcha.

I guess what I am looking for is the engergy I have available versus the slug weight and barrel diameter. I am not a physics major. I have no clue how to calculate that. I used to have the link to a spreadsheet that would give rough data like this.

Matt

These are the online calculators I use:

This one gives you instant results in Imperial/metric etc.

This one allows you to plot a graph of velocity vs muzzle energy for a given projectile.