DYI Ballistic Lab?

[DRNewcomb]

In the local Linux users' group we were talking about projects for the Arduino and/or Rasberry Pi micro computers and I started thinking of building a low-cost ballistic lab. In particular, I'm interested in monitoring the relative chamber pressures by means of a strain gage attached to the barrel over the chamber, a la the Oehler Mod 43. I roughly guesstimate that it would require about a 1 MHz A-to-D converter, which is faster than any I've seen OTS for either of the micro-computers above.

Just wondering if anyone has seen any reports of anyone making a do-it-yourself chamber pressure graphing device?

 

[bigedp51]

I do not think the software will run in Linux because it is Windows base. Below are some links to PressureTrace II system.

PressureTrace II
http://www.shootingsoftware.com/pressure.htm

Below PressureTraceII being used

5.56 vs .223 – What You Know May Be Wrong
http://www.luckygunner.com/labs/5-56-vs-223/

 

[DRNewcomb]

Thanks! Use of Linux wasn't the issue. It was if one could build an inexpensive pressure profiler out of readily available components. I was not aware of the RSI system. I've used an Oehler Mod 35 chronograph and knew about their Ballistic Lab system. I was thinking of buying a Chrony. Now, I think I like the looks of the CED M2 chronograph and might start with getting that and then working my way up to the Shooting Lab, as the shooting piggy bank permits.

 

[itchyTF]

I have a PT II system and I certainly think it's good for comparing loads but I have always wondered about absolute readings. Your installation of the strain gauge might not be "perfect" along with (how many?) other variables. Even if a certain load was tested in a lab, your chamber & barrel is different therefore the pressure may be different. Just wondering.

 

[DRNewcomb]

None of these systems measure actual internal pressures. They actually just infer pressure from the strain (expansion) of the barrel near the chamber. They can only get close to actual pressure numbers by comparison with a standard cartridge. Even this can't be exact because of differences in chambering, rifling, phase of the moon, etc. What this type of profiler is good for is getting a view of the internal ballistic efficiency of a load as well as the consistency of performance. An ideal loading would produce a large area under the curve without exceeding maximum pressure and also produce the same results with each shot.

I suppose one could install a pressure sensor by drilling and tap a small hole into the barrel at the chamber and installing a piezoelectric probe but it would have to match the inside of the camber wall perfectly or you'd blow out every case you fire. This is what happens with copper and lead crush gages. You have to clean out the chamber after each round tested.