Pressure Traces:PN45 IMR4227 250ftx Sabotless

[TGinPA]

Pressure Traces:PN45 IMR4227 40-55gr 250ftx Sabotless

Continuing testing powders with faster burning rates, Today, I tested the load above.
Gage and Module Manufacturer = RSI USB model
Trigger Sensitivity = 2, Strain Gage Voltage =4.9 Gage Factor =2.1 PSI Correction Factor: 0
Barrel Temp = 60-65 degrees F. measured at the sensor (IR). Rifle Stand: Caldwell Lead Sled
Altitude: 450 ft Chronograph: Chrony Alpha Model 8 ft from muzzle. (13 fps added to all recorded velocities to correct for distance of chrony from muzzle.)
Barrel Type: PacNor .45 Cal Muzzleloader Barrel OD = 1.06 in Barrel ID = .452
Breech Plug:Savage Std. (screw-in ventliner) ventliner orifice .032in. Sensor dist fm BP=1.1 in. Bullet Diam.= .458 in. Bullet Type = Hornady 250ftx resized to .448 Bullet weight = 250gr. ,knurled. Sabot: None. Wads: Lubed Wool over .462x.060 fiber.
Powder: Upper Panel: T1= IMR4227 40gr., T3=IMR4227 50gr.
Lower Panel: IMR4227 55gr., Primer :Fed 209
Shot fm dirty barrel. This load seemed safe in my barrel under the test conditions but may not be so in other conditions.



Compared with the 5744 traces recorded on 3/29, grain for grain, XMR5744 gave higher peak pressures and faster rise times than did IMR4227. Yet velocities at each matching load level were very close at powder weights of 40 and 50grains. In my barrel, with this bullet and powder, it is likely that 2600fps might be reached without excessive pressure generation.

For smokeless muzzleloaders, IMR4227 seemed to lose its attractiveness due to a a number of issues: First,when used as a propellant in 50 cal. barrels, inconsistent ignition caused occasional misfires. However,in PN45 barrels, pressure is more easily generated, aiding ignition maintenance in powders which do not ignite easily. Second, in earlier testing with sabotted loads, I had sabot disruption at pressures below the point of useful velocity using 200gr bullets. Removing the sabot eliminates that problem. At the time, Edge commented that IMR4227 might still be useful in single powder sabotless bullet loads. IMO,today’s numbers tend to confirm his view.
TG

[Savage Shooter]

60gr would be the "predicted" place to be with this load.

At 60gr 2nd spike should be pretty much gone.

Speed @ 60gr predicted at 2750fps and pressure estimated at 41-43K, this powder is making about 680-700psi/gr and will increase some as more is used so would need to work up to see if about 2700 to 2750fps is possible. Speed is making about 46fps/gr so would need to watch this as you go up (if it quits making this speed per grain it is maxed). Would estimate pressures in the 42K range at 2750fps.

Loads like this can make extremely low ES when correct powder volume is reached.

Good job TG

Thanks
Mark

[ET]

Mar 30, 2011 14:02:42 GMT -5 Savage Shooter said:

60gr would be the "predicted" place to be with this load.

At 60gr 2nd spike should be pretty much gone.

Good job TG

Thanks
Mark

Savage Shooter

I seem to be at a loss here with your reasoning of increasing the load that would reduce the secondary spike?
Watching as the peak pressure increases between the 2-traces the secondary spike also increases.
Would really appreciate knowing why you feel this would tend to reduce the secondary spike?



Ed

[Savage Shooter]

Mar 30, 2011 16:28:59 GMT -5 ET said:

Mar 30, 2011 14:02:42 GMT -5 Savage Shooter said:

60gr would be the "predicted" place to be with this load.

At 60gr 2nd spike should be pretty much gone.

Good job TG

Thanks
Mark

Savage Shooter

I seem to be at a loss here with your reasoning of increasing the load that would reduce the secondary spike?
Watching as the peak pressure increases between the 2-traces the secondary spike also increases.
Would really appreciate knowing why you feel this would tend to reduce the secondary spike?



Ed

It is running out of powder with both loads, hence the drop to near zero. At the higher load there is "more" powder behind the curve to reignite, hence higher spike. When you get to optimum load the entire load column increases in speed to "catch up" with bullet. If you do not exceed desired peak first a spike like this can pretty much be eliminated with MORE powder.

Only testing up to the point where peak is either aproaching unsafe or uncomfortable (recoil) level will confirm this with any powder. IMO should be looking for a 43-45K load minimum for sabotless needs.

[moto357]

assuming H4227 and IMR4227 are similar, a little over a year ago i was looking for load data and was limited to using pistol cartriges since they were the only ones using this powder, as well as finding a cartrige with a full case. i laugh at myself a bit, although glad i was on the safe side of things. i gave myself a limit of i think 38gr and a 250xtp sabotless. found 33 and 34gr to be a sweet spot. also noticed no ignition problems and i was shooting in 20's and 30's for temps.

just wanted to add also that its nice to see tangible results of whats going on, thanks again for the info

[ET]

Savage Shooter

First off “Thanks” for the courtesy of a reply.

I can understand the increase of overall mass to the load with more powder but can’t see how this would discourage the bullet of racing further ahead of the powder load through additional acceleration applied from pressure buildup.
I have no experience dealing with sabotless loads so I can’t say if the bullets level of obturation would play a role here.
Definitely something I need to pay more attention too for future learning.


Ed

[Savage Shooter]

Mar 30, 2011 20:04:27 GMT -5 ET said:

Savage Shooter

First off “Thanks” for the courtesy of a reply.

I can understand the increase of overall mass to the load with more powder but can’t see how this would discourage the bullet of racing further ahead of the powder load through additional acceleration applied from pressure buildup.
I have no experience dealing with sabotless loads so I can’t say if the bullets level of obturation would play a role here.
Definitely something I need to pay more attention too for future learning.


Ed

Key is that "EVERY" powders burn rate increases as volume of powder increases.

Absolutely obturation is one of the biggest factors. As a matter of fact I asked TG to trace this same volume but with the 200 in sabot, if pressure jumps up or stays close to equal with 50gr lighter bullet then obturation is factoring in more due to "time of rise". If this powder is not rising quick enough to create enough obturation to seal building operating pressure then it won't make any difference how much you pour in.

But if pressure turns out to be appropriatly less then the bullet mass weight is the "controlling" factor.