TGinPA Pressure Traces

[dannoboone]

In going through his pressure traces to check out single powder
loads for a 275gr bullet, I noticed quite a difference in
pressure when traced at different times:

On 04/24/2013, temp 58*, a load of 93gr of 3031 was used. He
used a veg wad with that load which produced 37517psi. This
was only one shot, Trace #22g)

On 09/24/2013, temp 63*, the same load with veg wad averaged
43753 for four shots. He had a pound down over 50000psi but
I'm not considering that one. Trace #13h)

I have no idea if this was the same rifle, or if he sized his
bullets tighter for the September test. However, 6,000psi
difference is a LOT.

It might be a good idea for anyone using another's traces to
back down 10 or more grains!

[ET]

It appears TG was starting to experience adhesive failure on the strain gauge with his first single trace in April with this load.
Then after strain gauge replacement the second set of traces in Sept. showed more accurate higher pressures. I would trust the second test over the first one for accuracy.

Ed

[AJ]

I have seen 5k psi differences with the same load just due to bullet fit. It was a 2 finger seat vs both hands giving it all I had to get it seated. I am not a small guy. Does it mean if you are running a 40k psi load and have a tighter fit bullet your gun will blow up? I highly doubt it but very doubtful it will print to the same POI as the others.

Folks should not use the pressure traces as a loading manual. They are great for reference but are nothing more than a data point. It is up to the user to evaluate this information and determine what route they want to take.

[ET]

Jul 20, 2019 20:23:05 GMT -5 AJ said:

I have seen 5k psi differences with the same load just due to bullet fit. It was a 2 finger seat vs both hands giving it all I had to get it seated. I am not a small guy. Does it mean if you are running a 40k psi load and have a tighter fit bullet your gun will blow up? I highly doubt it but very doubtful it will print to the same POI as the others.

Folks should not use the pressure traces as a loading manual. They are great for reference but are nothing more than a data point. It is up to the user to evaluate this information and determine what route they want to take.

I basically agree with what you say but it can be a reasonably accurate tool as well if the operational functions are understood. Here I will be using the Load Verification part of the program to verify all is functioning properly at different points of usage. Yes it's up to the user to decide what he wants to do with this information.

Ed