Hello Denton
I mailed Jim Ristow about five minutes ago, and as I see you visiting this site right now, please let me ask you this:

the test strip is to be glued above the center of the chamber. SAAMI's voluntary performance standards (sect.III, cf rifle, p.132) show the center line of the transducer .175" from the bottom of the neck of the cartridge.

I do not expect the same results with the two systems, but would it not be adviseable to position the pressuretrace gage in the same place as SAAMi is doing it ?

Thank you.

Good question.

I think you will get pretty much the same pressure reading anywhere from the mid-point of the casing, to the point that brass is annealed. Mine are mounted just a little forward of the halfway point, to get away from the external shoulder of the barrel. Generally, edges and corners tend to not behave exactly like the rest of an object.

I do know that if you go forward of the shoulder, readings will be different. CIP in Europe does their pressure measurements at the mouth of the cartridge, and that does make a difference.

My preference is to mount the gage near the bottom of the barrel, and to relieve the stock a bit so that the stock is not in contact with the gage. You can drill a small hole in the bottom of the stock, and get a snap-in hole plug, so you can have access to the connector when you want it.... assuming they left you more than an inch of wire. Another choice is to mount the gage on the side of the barrel, and to mortise out a tiny pocket in the top of the stock, next to the barrel.

Recoile tends to disconnect the connector, so I usually use some electrician's tape to anchor the wire to the receiver.

Thank you for your explanations, Denton. Jim answered as quickly as you and suggests to introduce a factor to create comparability. Problem is the more inponderabilities are involved the more difficult is the hunt for the correct factor.
The question is (as with chronographs) how to calibrate a test device. When PACT recommends to shoot a quality rimfire round through the system, will there be a test load recommended ?

Here is Jim's answer where his last scentence seems the most important to me:

They are talking about Piezo systems. Entirely different technology.
Strain gage systems measure pressure fro the actual expansion of steel around the chamber. Pressure can be measured anywhere between the head of the case to the shoulder. Since you cannot get over the case head end on most actions without interference from the action threads, you almost always end up between the mid point and the shoulder.

With Piezo systems powder granules blowing into the pressure hole can interfere with good readings. Perhaps they drill Piezo holes near the
shoulder to get less powder interference.

Piezo is not as accurate as many people seem to believe. There is currently an ongoing series of articles in Varmint Hunter Magazine by a recognized instrumentation expert from Tektronix corporation you might want to check out. The magazine is hard to find without subscribing but I am sure they would send you the back issues you
have missed.

Even if you think Piezo is correct and the umbers don't match, just enter a correction factor and they will.

The reason for purchasing PressureTrace is not just for PSI data.
PSI tells you little information of value. It is the shape of the curve measured in real time that is of value.

Jim Ristow
Recreational Software, Inc.
Email: rsi@commspeed.net
http://www.shootingsoftware.com
"Better shooting thru computing"

Well, I guess we've come full circle. I'm the guy that wrote the article in Vermint Hunter. ROFL.

Hello,

We have also a big discussion about this subject in our forum, it should be at least readable for waitaminit.

http://www.tirmaillyforum.com/mildot/viewtopic.php?t=518

Denton, I will write you a mail in the next few days. I need your support in this matter.

Regards
Makalu