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Post by TGinPA on Jan 31, 2011 16:58:31 GMT -5
PN45 Pressure Trace:4759 & resized 300gr. Rem jhp sabotless Soon obtaining my PacNor 45 barrel, I worked up to a load using IMR SR4759 (Tin can) and a 300 gr resized Rem JHP, sabotless with wad. With 35 gr. 4759 I could achieve 1-1 1/2 inch groups and velocities averaging 1950 fps. Because there were questions in regard to peak pressures I might be generating with this load, I was reluctant to go higher. Once I set up the Pressure Trace recording, I tested this load and was surprised to find that peak pressures were slightly less than 40k psi. I was curious to see what it would take, using this bullet and powder, to generate 45k psi and what the velocities would be if I did so. My pressure trace setup is described in earlier posts. The upper set of traces show the incremental increases in pressure as I increased the load from 38 to 41 to 43 grains of 4759. With 43 gr. of 4759, I reached slightly above 45k psi. At that point 3 traces were obtained using the 43 gr. load to see how consistent the pressure readings were. The results are shown in the second set of traces. I have no good explanation for why one of the three pressure traces is clearly different in shape and peak pressures from the other two in this set. One problem I have when shooting sabotless is maintaining a consistent seating pressure, particularly if I knurl. In these tests, I did not knurl because to do so would have required that I use a mallet to seat the bullets. Though I noted no subjective difference in seating pressure (in the range of 50 -70 lbs), it might account for the difference. For my setup, if my measurements are accurate and if for a sabotless load in this barrel 45k psi is a reasonable upper safe pressure limit, then 43 grains of IMR 4759 reaches it with a resized 300 rem JHP. As always, the loads described and tested here seemed safe under the conditions of the tests but may not be so under other conditions.
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Post by Dave W on Jan 31, 2011 18:02:59 GMT -5
Good stuff! Have you by any chance shot N110 sabotless?
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Post by TGinPA on Jan 31, 2011 18:24:19 GMT -5
Not yet. I will put it on my "to do" list.
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Post by jeremylong on Jan 31, 2011 20:19:40 GMT -5
Keep it coming. Thanks.
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Post by ET on Jan 31, 2011 20:34:31 GMT -5
TGinPA Nice job on the traces and supplied data that is appreciated. Hope you don’t mind a question that is not insinuating in anyway but are you comfortable moving a load up to that registers 45K on your PT? Just asking what your thoughts are on this. From Richards’s communication with Mr. Ristow from RSI a SS barrel usually shows 2K less pressure than a Chrome Moly barrel. Then I also wonder if there is credence to the theory from Mr. Hartmut Broemel for pressure wave intensity increasing and moving with the powder burning as it propagates forward. Considering this is not a cartridge with a tapered shoulder trying to restrict/regulate peak pressure movement as it is being built it has me wondering if the current location of the strain gauge for a muzzle loader is actually where peak pressure develops. These are the reasons for my question. I will find an answer to my second reason for questioning when I begin my round of testing with a second strain gauge installed in front of the first. Again I reiterate that you are doing some nice work providing great info. Me I’m just a stickler for details that raises questions that might need answers. Wish I had a sheltered area like Richard to play in. Oh well the foot of snowfall forecasted Tuesday/Wednesday will occupy some outdoor time. ;D Ed
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Post by edge on Feb 1, 2011 10:03:49 GMT -5
Very nice!
One advantage of 4759 is that it is very bulky. Even tough it is a fast burner, it takes up a lot of room.....it is the opposite of Lil'Gun which takes up very little room making for high pressures.
As an example
50 grains of N110 takes up about 64 grains of H2O; 50 grains of 4759 takes up about 76.6 grains of H2O; 50 grains of Lil'Gun takes up about 52 grains of H2O.
edge.
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Post by TGinPA on Feb 1, 2011 11:57:55 GMT -5
ET: I knew this question was coming, if not from you, from someone else. Because I believe you are committed to performing pressure tests of loads in the future, I do fully appreciate your concern. The fact that I even collected the data hopefully should answer that question for you. IMHO, in general terms, no load is safe until repeatedly shown to be so and that requires the test of time . In particular, sabotless doesn’t give one the “blown sabot “ sign of excessive pressure. In that sense, any new load ever tested (particularly sabotless) has the potential for serious trouble. On the other hand, with smokeless muzzle loading, aside from the book loads, from one source, commercial data are hard to come by. The PT device adds a layer of safety, but not definitively. Given measurement of published loads with pressure readings in the same range, and given previous published admonitions from members of this board with vastly more experience than my own that 45k psi peak pressure was an acceptable maximum, I proceeded stepwise to that level with this load. As an added level of precaution, one could also use Quickload as a predictor. The major concern with a device such as the PT is its accuracy. If my sensor reads the peak as 10k psi too low, I am looking at 55k psi. Comparison of my data with other loads measured by others suggests that I am not that far off. Even in comparison with PT data obtained from others, without some calibrating standard (including temperature, load, and sensor position) the burning question will always be who is right? I am looking forward to your testing after the spring (summer?) thaw. I forget if you planning any PacNor 45 testing? Regarding Broemel’s theory, I have difficulty visualizing narrowly localized pressure waves dancing back and forth along the expanding gas column in a barrel. That regretfully reflects the limits of my education.
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Post by ET on Feb 1, 2011 16:24:43 GMT -5
TGinPA
Appreciate the response to my question and with what I deem an excellent answer.
I agree without say a known accurate comparison trace or known pressure of a specific load to reference for accuracy makes this type of testing a little open to suspect. But still a far cry better than just assuming what pressure is obtained by reasoning or even calculating. I also agree as you pointed out in your posts with the addition of saying results may not necessarily be the same in another barrel. So common sense should dictate a good margin for error or difference should be taken into consideration.
My testing will be done with the 50Cal and usually I get out/start shooting around Easter time (early April). My education level is not to any high degree either and I did question the credence of Mr. Broemel’s theory. The only way I can try to check out his theory is with a second strain gauge further out front and see what appears on a trace. From past experience with explosives I do know a shockwave (pressure wave) can be funneled and redirected back on itself. Combine that with Mr. Broemel’s theory and seeing a secondary pressure wave on a trace does raise enough concern/interest to investigate a little further. At this point in time and limited knowledge I can only see the circumferential barrel expansion affecting the strain gauge that can only be achieved with a returning secondary pressure wave.
In a way there is no absolute right or wrong for setting an imposed pressure trace limit because all the instrument shows is what it senses. For now a limit of trying not to exceed 40k is more my comfort zone. I hope you and Richard will continue your endeavor with pressure traces with the 45 Cal to help expand my learning even before I get my feet wet.
You guys are doing valuable work that many others will benefit from.
Ed
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Post by Jon on Feb 1, 2011 17:07:05 GMT -5
If I remember correctly when RB was doing his traces he said that 40K was what he felt was sabot limet And I think he was shooting for 45K sabotless. this I think was in a 50cal. Someone correct me if I am wrong? Jon
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Post by ET on Feb 2, 2011 16:41:37 GMT -5
Jon
I don’t remember RB’S exact words but 40K seems to ring a bell.
What I found interesting with the second pressure trace in this thread is as follows, T2 has the least peak pressure, fastest rise rate/time, the descent or rate of pressure falling is basically the same as T1 & T3 and T2 has the fastest velocity recorded. In a given load you would think the highest peak pressure would produce the highest velocity as seen in the first trace. So am I seeing a reversal occurring as the powder amount is being increased? I’m still scratching my head on this one.
Ed
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Post by rossman40 on Feb 2, 2011 16:54:03 GMT -5
IIRC a lot of RBs early testing was with the old formulation sabots prior to 2003, still a load in the 40k range would be about where you would want to be. Above 50k your still might be safe but perhaps flirting with disaster.
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Post by Jon on Feb 2, 2011 17:28:07 GMT -5
Et good question I saw the same. The traces give you a lot to think about. The difference in pressure with Richards traces bothers me some. Particularly because the gun I'm building now is going to be pressure sensitive being a small bore and not having load info to start with and that is the pressure trace I'm hoping to use. Jon
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Post by jims on Feb 2, 2011 19:02:54 GMT -5
Jon: You are correct about the smaller bores and pressure. My .38 was tough on vent liners, my .50 not at all so.
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Post by ET on Feb 2, 2011 19:31:25 GMT -5
Et good question I saw the same. The traces give you a lot to think about. The difference in pressure with Richards traces bothers me some. Particularly because the gun I'm building now is going to be pressure sensitive being a small bore and not having load info to start with and that is the pressure trace I'm hoping to use. Jon Jon There is interesting info provided by a PT if you are willing to look a little deeper in what it shows and try to decipher the info a little more. I can understand your apprehension because of the large difference that the unit Richard is using. If the unit has an option of using a USB cable instead of just wireless I would be inclined to start with that set up. By rights the recording of a PT should not reflect such a long ignition delay or pressure build up start seen with Richards Traces IMO. Now if you install the unit on your set up and eliminate the long delay I too would have more faith with the results. Ed
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Post by Jon on Feb 2, 2011 22:32:09 GMT -5
Ed thank you for the follow up I'll have to check if it is usb compatible. When I got the unit I sent it straight to Richard and He is out of town for a while. As far as interesting you are 100% right there is a lot of info that you can get from it. Jon
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Post by edge on Feb 3, 2011 11:54:29 GMT -5
I believe that the wireless aspect is only for sending from the Pressure Trace unit to the computer and NOT from the rifle to the PT unit.
With that said, the pressure is taken exactly in the same manner and only the complete data is then sent to the computer...but I could be wrong.
edge.
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Post by Jon on Feb 3, 2011 13:40:40 GMT -5
Edge. I think you are 100% right. Thats why I didn't it would make much differance. But who knows. There must be some reason for the pressure differance it's just figuring out what? Jon
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Post by ET on Feb 5, 2011 11:48:03 GMT -5
I believe that the wireless aspect is only for sending from the Pressure Trace unit to the computer and NOT from the rifle to the PT unit. With that said, the pressure is taken exactly in the same manner and only the complete data is then sent to the computer...but I could be wrong. edge. That’s true about the collected data from the PT unit using wireless. What needs to be taken into consideration is the collected data from the PT unit is now placed on a carrier wave for transmission to the computer. Here the carrier wave is removed leaving the data to be processed by the PT program. Now if for some reason the carrier wave frequency isn’t matched for transmission to reception then some of this data could become corrupted and inaccuracy could occur. Richard did mention that there were difficulties with communication recognition between the PT unit and computer. This also doesn’t rule out some outside interference affecting the carrier wave. To rule out or prove that any fault lies with the wireless setup and the unit has USB capabilities then I would be inclined to try using the USB setup. It will be interesting to see what shows up in the future. Ed
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Post by edge on Feb 5, 2011 12:33:36 GMT -5
I would suspect that the raw data is not sent, and even if it were I bet that it would be as reliable as any wireless network.
Since I use a wireless router on this computer and only some of what I type is gibberish ;D ;D I suspect that the wireless aspect has virtually nothing to do with the data....but I may be wrong.
edge.
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Post by ET on Feb 5, 2011 14:02:02 GMT -5
I would suspect that the raw data is not sent, and even if it were I bet that it would be as reliable as any wireless network. Since I use a wireless router on this computer and only some of what I type is gibberish ;D ;D I suspect that the wireless aspect has virtually nothing to do with the data....but I may be wrong. edge. Edge No gibberish here and never said raw data. My goat is not getting let out to butt heads with yours. ;D ;D Also want to openly express a special thanks to TGinPA for responding to my request of sending me one of his unaltered PT files in original format to explore some of the features of the PT unit. No problem to open the file and use certain functions/features available. So PT files can be shared for comparisons with those that have a PT program of the same version. My request was expressed openly and now my thanks is also. Ed
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Post by Richard on Feb 7, 2011 17:25:06 GMT -5
Well, I am back from EDGE's snow country (NJ) and am glad to see TGinPA is providing some good information. I wish I knew why his data appears higher in PSI than mine? By he way, there is not USB compatibility with the Trace unit and the computer. It is strictly wireless! And as Edge has indicated, I don't think the difference is in the communication between the two. From TG's pic, his strain gage is located the same as mine. And...........like the instruction say, if there is a problem with the gage or its mounting, the unit will let you know? Plus, the fact that my traces are "typical", would indicate (to me that is) that things are working OK? There is a feature where you can correct the readings.............For instance, I could increase my reading by 10,000 psi. However, unless I knew my reading was wrong, based on "factory data", I would be reluctant to do so. With a cartridge, for instance, I could use information from reloading manuals to get the unit on track.........but with these ML's............ In the future, I may set up a gage on my 6mmBR rifle and get some readings that can then be compared with book loads. Right now, I'm taking a break from all this "tech-no" stuff Richard
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