Planning on buying a PT II, but before I do I need to decide on the platform.
Contender seems like a simple (spendy) choice.
Any other ideas?
I do have a family member who can thread / ream for a donor bolt action, and being a single shot test bed would be the guns only purpose.
Thanks :)
To be honest, it seems like you are going to be looking at about $250-$300 per barrel no matter what platform you choose. The contender is faster to swap barrels, but potentially at a lower number of readily available cartridges at lower price. The Mauser or Remington 700 would probably offer the widest selection, especially is said family member can turn a barrel for you. Savage would be a compromise as the savage barrel system is pretty straightforward to change.
Have a few Mauser actions, just finding a blank in 10mm.
I'm not really familiar with 'world' rifle chamberings, aware of any that would only need a ream?
The TC does seem like the simplest, but finding one...
Usually the trace transducer needs a rounded surface to be mounted, It would be possible to use just a barrel in a fixture with a firing pin to set the round off. I thought about using a S&W barrel but an EAA barrel may be better.
The other thing is it needs to be calibrated to known pressures...it can be useful though.
Good luck!
Duh! I was thinking 'Glock' chambers! Not all auto loader's chambers are square...
I could use my Parker's (headspace issues) barrel, though devising a method of safely sealing the chamber might be more trouble than it's worth.
This is progress :)
I gotta think I could replicate this pretty cheap with a Raspberry Pi or Arduino board.
Looks like I can buy a 5-pk of sensors on ebay for $25.00. I would need to figure out a connector and what i need to get it hooked up to the IO headers on one of my Pi's.
Gotta try one out.
My Sketchup-foo is very bad, so apologies!
I think what's pictured below should be pretty straightforward to build. I'd use two barrel clamps, instead of the one pictured.
(http://webcity.net/benchrest/PTIIplatform1.jpg)
(http://webcity.net/benchrest/PTIIplatform2.jpg)
Only thougtht, what's the legality of constructing something like what's pictured above?
Anything you can buy legally, you can build.
So make sure there is a hand grip and you can pick it up and fire it, however poorly, with your hands. That way no-one can say it is an SBR.
If you are really concerned, contact a lawyer experienced with firearms law and have him advise you. $200 well spent.
Quote from: Benchrst on November 29 2015 07:43:02 PM MST
Have a few Mauser actions, just finding a blank in 10mm.
I'm not really familiar with 'world' rifle chamberings, aware of any that would only need a ream?
The TC does seem like the simplest, but finding one...
I agree that the TC seems the simplest. Lots of custom makers of those too.
Not sure what you mean by a ream. I get reaming the bore to a larger caliber, but what about the chamber? Wouldn't it have to be rechambered too? Maybe I don't understand and that's simply a matter of reaming too?
I'm assuming the Mauser actions are based on rifle platforms? If they are, or even if you're simply going to mount the action to some type of homemade base, I am curious what barrel length you're planning on?
Just re-reading through this thread.
Benchrst, you absolutely have to have a round barrel with the bore centered in the barrel for the PE transducer to give accurate readings. If the strain on the sensor isn't uniform due to differing barrel thickness across the test area, the readings will be inaccurate.
Quote from: sqlbullet on December 06 2015 09:27:19 AM MST
Just re-reading through this thread.
Benchrst, you absolutely have to have a round barrel with the bore centered in the barrel for the PE transducer to give accurate readings. If the strain on the sensor isn't uniform due to differing barrel thickness across the test area, the readings will be inaccurate.
Thanks sqlbullet.
Yes, I'm very aware of the necessity of a round chamber, of consistent wall thickness, that is aligned with the bore :)
A family member has milling equipment, and the current idea is to turn down a LW barrel.
:)
Just in the off-chance, are you near Wisconsin?
I have a 10mm Encore barrel. Heck, I even have a strain gage epoxied to it.
I also have the pressure trace unit, and I succeeded to get one trace that looked like it was supposed to, then the error message told me to contact my dealer and was not able to make it go anymore.
A combination of time spent messing around, not getting it to work, plus an hour each way to the range, and generally not enjoying the experience has lead me to put off the project.
Greg
Greg
Close, SW Washington ;D
It's a bit discouraging to hear your experience with the PT - I'm hoping mine's better.
Want to sell the Encore barrel?
:)
Nope... Too purdy ;D
(http://www.spanielsport.com/photos/i-4KxdMGG/0/XL/i-4KxdMGG-XL.jpg)
The gage...
(http://www.spanielsport.com/photos/i-m77fPJ8/0/XL/i-m77fPJ8-XL.jpg)
The wires/connectors are fairly delicate. They gave my big mitts fits. I wish they would have used plain old phone connectors, positive and about 10 times the size.
Greg
Greg
WAY too purdy!
:)
Oh boy that is really really nice......
Quote from: Geeman on December 06 2015 11:47:30 AM MST(http://www.spanielsport.com/photos/i-4KxdMGG/0/XL/i-4KxdMGG-XL.jpg)
Gorgeous!
What barrel length is that?
Thanks everyone.
That is a custom 9" barrel. Even the lowly PPU ammo hits 1200 fps. 2" at 100 yards is possible with well assembled ammo, but crimping in a separate step is necessary.
Greg
Those strain gauges are $5/each on ebay in 5 packs.
I think you could add a MCP3008 A/D converter and a wheatstone bridge and add in some python code on a Raspberry PI and have one going for less than $100.
Gotta figure out a way to have time to play with these kinda things.
Quote from: sqlbullet on December 07 2015 07:45:33 AM MST
Those strain gauges are $5/each on ebay in 5 packs.
I think you could add a MCP3008 A/D converter and a wheatstone bridge and add in some python code on a Raspberry PI and have one going for less than $100.
Gotta figure out a way to have time to play with these kinda things.
A few considerations...
Something around .6 ms beginning of ignition to out the barrel.
There needs to be quite a few data points if you are going to attempt to plot the curve.
There would need to be a trigger to begin the event so data didn't overflow the ability to keep track of it.
Greg
That math is spot on for a 180 grain at 1300 fps from a 5" barrel.
The worst case scenario is short barreled magnums. A 44 magnum firing a 170 grain bullet from a 2" barrel only gives .33 ms sample window.
In the code I am envisioning I will use a noise floor function. Once a value exceeds the noise floor, I will capture a timestamp, and then on each subsequent sample, the clock value and magnitude until the value descends below the floor. The entire array will get dumped to database once the "event" is over. I have written similar code for another project, just at a much, much more glacial sample rate.
The first issue though is the MCP3008 only runs 200,000 samples per second at 5V. That means for a .6ms window, I can capture 128 samples. In the 44 magnum worst case, I will get only 67 samples.
The second issue I am going to have to deal with is the MCP3008 is only a 10bit AD converter. If I assume a 100,000 PSI ceiling, then I will only be capturing to the nearest 100 PSI.
Here is a mock trace from data I pulled from a 6.8 PPC load adjusted to 67 samples over 1ms with a resolution of 100 fps. This is still very usable.
(http://fellingfamily.net/images/mockTrace.png)
I just need to get some sensors, build the bread board, write some code and get to the range. Good news is I can power the whole thing pretty easily with a battery.