Discussion on pressure traces Jan. 19

It is waaaaaay over my head BUT I am listening. Thank you Rusty

No idea if there is any difference due to weather conditions but the times I have tried tweaking loads in the .45 by substituting CCI's for Feds-no measurable gain or loss in accuracy.

What is the safe pressure range for these barrels and how does this compare with CF rifles?

Also, what is the secondary pressure rise toward the end of the graphs caused by? I would not have expected this.

thx,

Garland

Ed.........Yes, a recessed breech plug. That is all I use. The depth is about 1/2".

I am going to leave the barrel pressure rating up to Edge to discuss. I believe, for purposes of this board, we were going to limit safe pressures to be under 45,000 psi. ? These barrels are built with the same steel as CF barrels. We know that pressures in some CF cartridges have SAAMI specifications of 65,000 psi. Therefore the actual burst point is probably over 100,000 psi
Richard

Thanks for running that test

I would agree on the pressure that that barrel can take with a few caveats.

The rear sight screw hole if you have one is in the main pressure area, and assuming the pressure does not get into the BP snout area as the metal is much thinner and there are ID and OD threads which is a concern.

I still can't figure out why my pressures and that of TGinPA are so much higher than that shown by Richard's traces!



edge.

For comparison, here are pressure traces of two loads I tested today which were recently recorded by Richard. The 10k psi difference in his numbers and mine persists and I wish I knew why. I had planned to get more data on these two loads. But I lost several hours of shooting time because of intermittent snow and a bad connection between the sensor and the cable connecting it to the recording equipment. I had also planned to shoot a load with N110 55gr and the 200gr xtp. Given the pressures that I saw with 50 gr N110 and the 200gr xtp, I think I will wait a while before I go there. The loads I tested seemed safe in my gun but might not be under different conditions.

Computer: Dell Inspiron Mini Notebook Gage and Module Manufacturer = RSI USB model
Trigger Sensitivity = 5 Strain Gage Voltage = 4.9
Gage Factor =2.1 PSI Correction Factor: None
Barrel Temp = 63-64 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
Breech Plug: Pa Machine Recessed (screw-in ventliner)
Barrel OD = 1.055 in Barrel ID = .454
Bullet Diam.= .450 Bullet Type = Hornady 10 mm 200gr. xtp Bullet weight = 200 gr. unknurled
Sabot: Harvester Light Blue
Powder:
Trace 1: N110 50 gr. Primer :Fed 209
Trace 2: N110/H322 13/55 gr. Primer :Fed 209
Shot fm clean barrel, 1 patch Bore Shine, 1 dry patch

15 minutes south of Pottstown, an hour south of Allentown.

Are you using that barrel you had shortened Richard?

There may be a discrepancy but the informative thing to me is that it is consistent. From all I have read here, and I've been following all of this closely, my personal opinion is that Richard's traces do appear to be suspiciously low and I think the 10K psi number is probably a decent ballpark. Without a reliable known standard load confirmed in a professional-quality setup, this is as good as any of us can do.

I feel comfortable adding 10K to the traces (being on the conservative end!) and interpreting from there. Thanks to TGinPA for the wider perspective as well.

Based on all of this I will be trying the 15/55 VV110/H322 duplex, which would gain me about 100 fps over my current load, and I feel a lot safer doing so than before Richard and TG went to all of this work (it's still on me though!).

Many thanks to both of you for providing this information.

Thanks to both of you for this valuable data!

The duplex pressure is low on both barrels and the second bump is fairly large on both also.

To me it might be reasonable to assume that the booster should be increased to see the result on the second bump...and the main pressure is low to start with.

If you left the H322 alone but added a grain or two of N110 it should raise the primary pressure and hopefully reduce the second bump.

Just a thought.

edge.

Edge: As you thought, increasing the booster by a few grains increased velocity by almost 100fps, increased peak pressure by close to 3k psi, and decreased the secondary pressure spike significantly. This load seemed safe in my gun but may not be in other conditions.

Computer: Dell Inspiron Mini Notebook Gage and Module Manufacturer = RSI USB model
Trigger Sensitivity = 5 Strain Gage Voltage = 4.9
Gage Factor =2.1 PSI Correction Factor: None
Barrel Temp = 63-64 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
Breech Plug: Pa Machine Recessed (screw-in ventliner)
Barrel OD = 1.055 in Barrel ID = .454
Bullet Diam.= .450 Bullet Type = Hornady 10 mm 200gr. xtp Bullet weight = 200 gr. unknurled
Sabot: Harvester Light Blue
Powder:
N110 15gr. H322 55gr. fed209 primer

Very cool, thanks for doing that so quickly TGinPA ;D ;D

I agree with Richard that there does not appear to be any pressures that are too high. I wish that they correlated better.

The nice thing about the Traces is it gives you a slightly different perspective from the chrono!
A duplex may be high in velocity and low in pressure, but it may not really be ideal. The two extra grain clearly made a better trace. Too fast then lower the total charge but you really don't know the correct percentage without the trace!

This is some really great information from both Richard and TGinPA

edge.

Richard: I think that after I add velocities using the "velocities" button on the left side of the pressure trace graph, the calculated OBT and exit times automatically appear. On my next run, I will check it out to be sure.
Jon: The Pressure Trace Operating Manual describes the crossmarks as bullet exit points on page 11. If you are interested, I think you can download the manual from the RSI website. Hope this helps.

Been following this and made me remember back when RB was doing this and talking to me and SW daily on 50 caliber duplex loads we did not see peak velocities until the peak pressure moved out to .5 on the time bar.

These loads still seem to be peaking at about the same time. Note RB's old traces and notice how much later the duplex peaked than the single load increasing time under the curve. This may not be the same at all with the .45 but worth noting.

One of the things we learned to pay the most attention to was the point at which the booster made the load "come alive". This was all we had to go by with NO pressure info at all. All we could do is compare the loads to tested similar cartridge loads best we could.

We would make 2 gr increases and the load would be bumping along and gain 25fps per grain of booster increase then all at once a 2gr increase would jump speed up 150+fps. From this point I watched for the load to basically "flatline" on speed with little or no increase with increase of booster. RB first thought 16gr of booster was max.........If you will remember this is what gave birth to RB's 2nd generation of duplex with more booster than we had thought possible in the infancy. Looks like just what TGinPA has noted.

The first .50 duplexes we used were 8/67 and 10/65 n110/h322 loads and we noted the load being more temp sensitive in this range also. SW probably remember more than I since he was the one out in the cold shooting them.

I will bet the farm that this is the same thing you are seeing now in the secondary spikes. When the optimum load & powder balance is achieved I bet these will disappear.

I was looking for any traces using N130 that Richard was testing earlier due to thinking I remembered it being a touch faster fps at same weights than h322 in the .45.

Probably out in left field, but used to staying there anyway.......going back to sleep now as my typing has exceeded my knowledge.