Calculating pressure: How?
- Thread starter Milsparro
- Start date
Canam, the data looks good to me, no reason to question it that I can see. Looking at this specific load I'd consider increasing the charge a bit - ballistic efficiency will improve with a stouter load that produces higher pressure.
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21k is SAAMI max, your load runs at 8393. See the results box, bottom left, or red line on graph.
That's a D'oh moment there, yah.
I got Quickload a short while ago and am confused by the results. Perhaps it doesn't work well with an undersized hollow base bullet? Not sure what to make of it.
Here are some results for .41 Colt.
Gun is a Colt 1894 DA with a 4.5" barrel although I gave 6" as the barrel length when measuring from the breach face.
Powders are Alliant Unique with powder charges listed in early reloading manuals (so I figured these would be safe) and Ramshot True Blue which I ran across recently and like a lot.
Bullets used a pure lead 185gr Hollow Base from a Rapine mold, I did my best to input the dimensions into quickload (there is actually a hollow base input feature) but the softwhere does not grasp an undersize .386" bullet obturating to .408" so I listed the bullet diameter at the full groove width.
Cases are Starline .41 Long Colt.
Lets start with Unique. I was using 4.4gr with 684fps on average, note the fps Quickloads gives!
To actually achieve 684fps I had to drop the charge to 3.2gr.
Here is another load I recall being listed as the MAX in older reloading manuals, not even close to safe according to Quickload.
Now for Ramshot True Blue. The load I settled on was 5.4gr with an average of 750fps, which Quickload determines to be too hot.
To get 750fps I had to drop the charge to 4.5gr.
Here's one more showing Unique near 750fps using 3.6gr. It shows a lower peek pressure with a slower pressure curve, which is opposite of what I figured between these two powders.
Here are some results for .41 Colt.
Gun is a Colt 1894 DA with a 4.5" barrel although I gave 6" as the barrel length when measuring from the breach face.
Powders are Alliant Unique with powder charges listed in early reloading manuals (so I figured these would be safe) and Ramshot True Blue which I ran across recently and like a lot.
Bullets used a pure lead 185gr Hollow Base from a Rapine mold, I did my best to input the dimensions into quickload (there is actually a hollow base input feature) but the softwhere does not grasp an undersize .386" bullet obturating to .408" so I listed the bullet diameter at the full groove width.
Cases are Starline .41 Long Colt.
Lets start with Unique. I was using 4.4gr with 684fps on average, note the fps Quickloads gives!
To actually achieve 684fps I had to drop the charge to 3.2gr.
Here is another load I recall being listed as the MAX in older reloading manuals, not even close to safe according to Quickload.
Now for Ramshot True Blue. The load I settled on was 5.4gr with an average of 750fps, which Quickload determines to be too hot.
To get 750fps I had to drop the charge to 4.5gr.
Here's one more showing Unique near 750fps using 3.6gr. It shows a lower peek pressure with a slower pressure curve, which is opposite of what I figured between these two powders.
Now you understand why Unique is so popular, and I'd say you might need to throw out some of those old reloading manuals. Or maybe not. Quickload is eye opening in many respects, but Quickload has some quirks when dealing with low pressure pistol cartridges and hollow base bullets.
To actually validate Quickload calculations you need to put those loads through a chronograph. If you find that the measured velocity is close to the Quickload estimated velocity then you will be as sure as you can get that the Quickload estimated pressure for that load is correct also. If you have a 4.5" barrel then you need to enter 4.5", and not measured back to the breech face. Measuring from the breech face will screw up Quickload's estimated velocity.
Hint: In the smaller capacity pistol cases that I have tried, (.38 spl, .455 MKII webley) Quickload over-estimates velocity by about 5-10% and I infer that pressure is somewhat overestimated then as well. I haven't tried .41 colt.
Also play with the seating depth inputs on Quickload - I found it shocking how a tiny change in seating depth will make remarkable pressure spikes if you are already close to the limit. I am way more careful with my OAL measurements now than i used to be.
I suspect that the high pressures you are seeing may be related to the volume of the hollow base not being calculated properly. I saw the same thing on webley 265 gr HB .455 bullets. I "fixed" it by calculated the volume of the hollow part of the HB 265 gr webley bullet and made up bullet dimensions for a flat base and adjusted entered seating depth in Quickload so that the case powder volume with bullet seated was close to actual. I found this worked better than just ticking the Hollow Base box and letting Quickload decide the actual volume that the hollowbase contained. Hope that makes sense.
To actually validate Quickload calculations you need to put those loads through a chronograph. If you find that the measured velocity is close to the Quickload estimated velocity then you will be as sure as you can get that the Quickload estimated pressure for that load is correct also. If you have a 4.5" barrel then you need to enter 4.5", and not measured back to the breech face. Measuring from the breech face will screw up Quickload's estimated velocity.
Hint: In the smaller capacity pistol cases that I have tried, (.38 spl, .455 MKII webley) Quickload over-estimates velocity by about 5-10% and I infer that pressure is somewhat overestimated then as well. I haven't tried .41 colt.
Also play with the seating depth inputs on Quickload - I found it shocking how a tiny change in seating depth will make remarkable pressure spikes if you are already close to the limit. I am way more careful with my OAL measurements now than i used to be.
I suspect that the high pressures you are seeing may be related to the volume of the hollow base not being calculated properly. I saw the same thing on webley 265 gr HB .455 bullets. I "fixed" it by calculated the volume of the hollow part of the HB 265 gr webley bullet and made up bullet dimensions for a flat base and adjusted entered seating depth in Quickload so that the case powder volume with bullet seated was close to actual. I found this worked better than just ticking the Hollow Base box and letting Quickload decide the actual volume that the hollowbase contained. Hope that makes sense.
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A few things I can think of: Double check the case volume and length, it is off on some of the more obscure calibers. Also check the overall length is the same as your ammo. Another thing is that quickload has no way to take into account a .386" projectile rattling down a .410" chamber throat and expanding into rifling instead of getting squished down by the rifiling in a normal system.
When i started using Quickload I found that some of my "reliable" reloading data from old books and other sources was not so reliable as i had thought.
