|
|
Post by TGinPA on Feb 10, 2011 16:23:53 GMT -5
Pressure Trace N110/H322 14/61 gr & 200gr. SST After Herman’s posting Re: “blowed sabots” at Savage Shooters suggestion, I tested a load a bit less potent than Herman’s maximum from that post. Gage and Module Manufacturer = RSI USB model Trigger Sensitivity = 3, Strain Gage Voltage =4.8 Gage Factor =2.1 PSI Correction Factor: 0 Barrel Temp = 60-62 degrees F. measured at the sensor (IR). Rifle Stand: Caldwell Lead Sled Altitude: 450 ft Chronograph: Chrony Alpha Model Barrel Type: PacNor .45 Cal Muzzleloader Barrel OD = 1.06 in Barrel ID = .454 Breech Plug:Savage Std. (screw-in ventliner) ventliner orifice .033 in. Sensor dist fm BP=.596 in. Bullet Diam.= .448 in. Bullet Type = Hornady 200 gr 40 cal. SST. Bullet weight = 200 gr. ,unknurled. Sabot: Harvester Smooth Blue Powder: All Traces: N110/H322 14/61 gr. Primer :Fed 209 Shot fm clean barrel, 1 patch Bore Shine, 1 dry patch It has been stated that stainless barrels underread pressure by about 2k psi when compared with chrome-moly barrels. If so, then these traces suggest that this load generates pressures in excess of 40k psi which is close to the point at which sabots begin to fail. Looking at my traces, could the one low pressure trace be due so incipient sabot failure? The conditions under which I did this test may have been warmer than those experienced by Herman accounting for increased sabot stability he experienced at higher loads. It would be useful to know just how cold it was when he fired the loads he recorded. This load seemed safe in my gun but nmay not be so under other conditions.  |
|
|
|
Post by bteague on Feb 10, 2011 17:22:13 GMT -5
I do not understand how all this works so i have a few questions.TI1 shows lowest pressure by far.Why is the speed right with T and T3?Also you are showing bullet diameter at .448.Where did you get that?And did you include sabot in the weight of bullet?Billy
|
|
|
|
Post by dannoboone on Feb 10, 2011 19:13:59 GMT -5
Wow. I recall that load as being one for the .50 with a 250gr SST.
Always thought the 14/61 load would be too much for the .45,
even with the 200gr bullets. If one toned the load down a bit to
make it a 2800-2900fps load, the sabots would probably be ok.
Very interesting. Thanks, TG!
|
|
|
|
Post by ET on Feb 10, 2011 20:21:38 GMT -5
Oh-Boy Trace T1 is a puzzle for sure.
To be honest I don’t see a sabot disruption here because of the secondary wave generated.
I don’t see a disconnect to the strain gauge occurring either because the characteristic straight drop on the trace is not seen.
What I can offer is a plausible cause but can’t validate it.
What only comes to mind here is a bullet/sabot jump during the initial pressure buildup. I know it sounds weird but when I follow the trace, see that the max peak pressure isn’t reached, a slope decline of the initial peak pressure to flat line and then see the pressure rebuild with a secondary wave of significant value the only thing that comes to mind is the bullet momentarily outracing the pressure buildup from the powder burn. I can only see this happening if the bullet/sabot isn’t continuously resisting the pressure buildup process.
As I said I can’t validate or prove this and with my limited experience I can only come up with one possible explanation.
I don’t have a monopoly on possible theories so if anyone sees something different I’m open to suggestions for trying to understand what is happening here. ;D
Ed
|
|
|
|
Post by TGinPA on Feb 10, 2011 20:22:21 GMT -5
bteague: I was sort of hoping that someone else would respond to your question because I suspect my answers may not be what you are hoping for. In recording the traces, I provide the numbers I plug in so that those looking at the curves will understand what I am doing. My primary interest is in recording accurate pressure curves so that others more experienced that I can explain or interpret them. In answer to your first question, I do not know the answer. In answer to your second question, in a muzzleloader, I have a hard time knowing precisely what bullet diameter to use. With a bullet which starts by riding on the lands and obturating variably, the bullet diameter will vary between groove to groove and land to land diameter. I know that land to land diameter is close to .4485 in. I also know that I can barely get an annealed copper bullet resized to a measured .448 in.diameter down this barrel. So, I chose to use this as my bullet diameter. While obviously the bullet diameter is a determinant of pressure generation, I don’t believe that whatever value is used for bullet diameter in the program has any effect the measured pressure readings. The manual states that the bullet diameter is used in “velocity calculations”. I have yet to interpret exactly what that means. The reason I put that diameter into the program is to let everyone viewing this data know what numbers I used and to make any judgment they wish to make based on those numbers. In answer to your third question, no, I did not include the 8.7- 9 grain weight of the Harvester smooth blue sabot. It also has no effect on the pressure curve. RSI provides a downloadable version of their manual. If this interests you, get it and welcome aboard. My guess is that if you do, I will learn more from you than you will from me.
|
|
|
|
Post by Chris Champion on Feb 10, 2011 20:25:10 GMT -5
I've shot about a dozen 195g BX in my 45 with a 15/55 N110/H322 duplex that hovers right around 2900 fps. It seems like a consistent load and sabots do not look any more stressed than they do with a 63 or 64g load of H4198.
|
|
|
|
Post by bteague on Feb 10, 2011 21:23:36 GMT -5
TGinPA,One more question(for now)Does the + indicate where the bullet exits the barrel.And I doubt you will learn much from me.Some of this is way over my head.But i am going to try and follow along as best I can.Billy
|
|
|
|
Post by tar12 on Feb 11, 2011 7:13:30 GMT -5
TG you got any N-120? ;D
|
|
|
|
Post by TGinPA on Feb 11, 2011 11:01:12 GMT -5
bteague and ET: There is great temptation to discard traces which do not fit one’s expectations (cherry picking). A major problem with inconsistency which I experience with this device is a technical one due to the plug connection between the sensor and the cable connecting to the pressure trace module box. To me, it is no surprise that a connection such as this one is not very secure no matter how much tape and Velcro is applied to it. It has gotten to the point that before every test, I recheck the resistance of the cable output with a multimeter to be sure it is within spec. I am surprised by how often visually the connections appear normal only to find that the measured resistance of cable and sensor is out of spec. Correcting this involves jiggling and tightening the plug connection at the sensor. This is scarcely a scientific way to eliminate error. But it is all I can do. I have ordered a new cable to see if that eliminates the problem. Looking at the connection design, I doubt if that will help much. If it does not help, I suppose I could cut off the plug connector and directly solder the cable wires to the sensor wires. But that would mean possibly damaging the sensor and also losing the ability to disconnect the cable and use my barrel for hunting. If a tracing is obviously technically inadequate both in shape and pressure, I assume it is due to a bad connection and discard it and repeat. If there is any question in my mind that the trace has validity, I include it to let others speculate on what it means, knowing that what is recorded may well be due to technical artifact.
bteague: Yes the x is supposed to be the exit point.
Tar12: If you go back to the discussion of pressure traces from December 28, you will find several traces I ran with N120 comparing with traces done by Edge a year ago. In answer to your question, yes I have N120. Hope this is helpful.
TGinPA
|
|
|
|
Post by edge on Feb 11, 2011 11:04:46 GMT -5
I always used the full bore diameter for the bullet IE 0.458 with my 45 barrel.
edge.
|
|
|
|
Post by TGinPA on Feb 11, 2011 11:30:45 GMT -5
Edge: If there is no objection from others, I have zero problem with switching to that.
TGinPA
|
|
|
|
Post by tar12 on Feb 11, 2011 12:01:44 GMT -5
I could not find it.
|
|
|
|
Post by TGinPA on Feb 11, 2011 12:10:22 GMT -5
Re: Discussion on Dec. 28 Pressure Traces
« Reply #23 on Dec 30, 2010, 5:16pm »
|
|
|
|
Post by shooter on Feb 11, 2011 14:43:24 GMT -5
|
|
