Week four of Pressure Traces......
Jan 3, 2011 20:30:45 GMT -5
Post by Richard on Jan 3, 2011 20:30:45 GMT -5
DISCUSSION THREAD CAN BE FOUND BY FOLLOWING THIS LINK
I will say this, I am getting better acquainted with the Pressure Trace instrument. I'm still in limbo on the accuracy issue? I am getting the impression from Jim Ristow that I am doing things correctly. I actually got one set of traces in the upper 36,000psi range but you will see the results. It is easy to say these traces are on the low side, but then again are other traces possibly on the high side? I don't think we really know? What I do know is that when I present a group of loads, valid comparisons can be made between them. I would also like to not have to "tip/toe" around the Triplex loads. I am not saying they are the "greatest thing since sliced bread" or anything like that. But part of the reasoning by Jon was to be able to show via PRESSURE, that they are not dangerous. No more so than Duplex loads or excessive single powder loads. I all types of reloading, whether ML, metallic cartridge or shotgun.........Caution must be used. Our biggest danger, in my opinion, is not from excessive powder charges but from double loading.
Anyway, here is a look at what transpired today:
First of all, I started with a duplex to get the barrel warmed up and the results are evident.
For T-2b I went with 55 gr. of N-110 and you can see the sharp spike in pressure right out of the gate. Now here is the interesting thing: If you look at the first load, the average velocity was 2917 fps and average pressure 30,141 psi. Now look at the velocity for T-2b? 2940 fps with an average pressure of 36,101 psi. 23 fps faster with 6,000 psi more pressure.
T-3b utilized 55 gr. of N-120 with a 400 fps drop in velocity and 14,000 psi drop in pressure.
For T-4b I used 55 gr. of N-130 and the velocity dropped around 300 fps and the pressure around 5,000 psi.
None of these three single powder loads looked too good accuracy wise.
T-5b was the first shot after the barrel had sat for a while. I was not thrilled with the long time the pressure stayed low and then shot up at the end! I recalled Rossman talking about blowing the end of barrels off ;D. So, I declined to shoot any more of this triplex.
With T-6b I took the powders I used in T-5b (pre mixed them at home) and totally mixed them. Nothing super great but very low pressure.
T-7b.........a generic 64 gr. of H-4198............Look at the trace and note the same profile of this first shot as compared to T-5b.....Then the succeeding shots all nice traces. Funny, even though the trace line looked bad, the psi was right in line with the others. Sooooooooooooooooooooooo, I decided to go back to triplex and continue shooting it on the same target. The trace is shown on T-8b.
The last group was the only sabot less load I shot and you can see the low ES on that speed.
So there you have it! Am I worried when I pull the trigger on a Triplex load that I have researched and know the characteristics of the powders involved? Not at all. Nor am I concerned with some duplex load which I see has produced higher pressures. And so far, the 55 gr. N-110 load has shown the highest pressures I have recorded so far. And, there are now blown sabots either.
I don't know what the criteria is to allow me to post some numbers as it would make it whole lot easier to write this post?
Richard
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I will say this, I am getting better acquainted with the Pressure Trace instrument. I'm still in limbo on the accuracy issue? I am getting the impression from Jim Ristow that I am doing things correctly. I actually got one set of traces in the upper 36,000psi range but you will see the results. It is easy to say these traces are on the low side, but then again are other traces possibly on the high side? I don't think we really know? What I do know is that when I present a group of loads, valid comparisons can be made between them. I would also like to not have to "tip/toe" around the Triplex loads. I am not saying they are the "greatest thing since sliced bread" or anything like that. But part of the reasoning by Jon was to be able to show via PRESSURE, that they are not dangerous. No more so than Duplex loads or excessive single powder loads. I all types of reloading, whether ML, metallic cartridge or shotgun.........Caution must be used. Our biggest danger, in my opinion, is not from excessive powder charges but from double loading.
Anyway, here is a look at what transpired today:
First of all, I started with a duplex to get the barrel warmed up and the results are evident.
For T-2b I went with 55 gr. of N-110 and you can see the sharp spike in pressure right out of the gate. Now here is the interesting thing: If you look at the first load, the average velocity was 2917 fps and average pressure 30,141 psi. Now look at the velocity for T-2b? 2940 fps with an average pressure of 36,101 psi. 23 fps faster with 6,000 psi more pressure.
T-3b utilized 55 gr. of N-120 with a 400 fps drop in velocity and 14,000 psi drop in pressure.
For T-4b I used 55 gr. of N-130 and the velocity dropped around 300 fps and the pressure around 5,000 psi.
None of these three single powder loads looked too good accuracy wise.
T-5b was the first shot after the barrel had sat for a while. I was not thrilled with the long time the pressure stayed low and then shot up at the end! I recalled Rossman talking about blowing the end of barrels off ;D. So, I declined to shoot any more of this triplex.
With T-6b I took the powders I used in T-5b (pre mixed them at home) and totally mixed them. Nothing super great but very low pressure.
T-7b.........a generic 64 gr. of H-4198............Look at the trace and note the same profile of this first shot as compared to T-5b
.....Then the succeeding shots all nice traces. Funny, even though the trace line looked bad, the psi was right in line with the others. Sooooooooooooooooooooooo, I decided to go back to triplex and continue shooting it on the same target. The trace is shown on T-8b.The last group was the only sabot less load I shot and you can see the low ES on that speed.
So there you have it! Am I worried when I pull the trigger on a Triplex load that I have researched and know the characteristics of the powders involved? Not at all. Nor am I concerned with some duplex load which I see has produced higher pressures. And so far, the 55 gr. N-110 load has shown the highest pressures I have recorded so far. And, there are now blown sabots either.
I don't know what the criteria is to allow me to post some numbers as it would make it whole lot easier to write this post?
Richard