Re: A quick question regarding HP-38 and W231

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Antiquus wrote:
pokute wrote:In general, greater area means better energy transfer, and potentially greater velocity as a result. Note that peak pressure does not correlate with velocity potential, as is often wrongly assumed.
Explain to me about correlation, because "no correlation" seems about as incredible as "prefect correlation" in this instance.
What it means is that velocity is dependent on the area under the curve, which is independent of the peak pressure. A "fast" powder showing a peak pressure of 20ksi in a given test will result in a reduced velocity compared to a similar test with a "slow" powder with a peak pressure of 20ksi. The slower powder is able to supply a usable driving pressure for a longer period of time than the faster powder. Remember, these are dynamic processes, and the peak pressure is a single, instantaneous measurement.

Re: A quick question regarding HP-38 and W231

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So it's not only how much pressure, but also when it occurs. A powder suitable for a 4" pistol barrel is probably not suitable for a 20" rifle barrel, or a 30" shotgun barrel. Milliseconds matter in this application.

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Re: A quick question regarding HP-38 and W231

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pokute wrote:
Antiquus wrote:
pokute wrote:In general, greater area means better energy transfer, and potentially greater velocity as a result. Note that peak pressure does not correlate with velocity potential, as is often wrongly assumed.
Explain to me about correlation, because "no correlation" seems about as incredible as "prefect correlation" in this instance.
What it means is that velocity is dependent on the area under the curve, which is independent of the peak pressure. A "fast" powder showing a peak pressure of 20ksi in a given test will result in a reduced velocity compared to a similar test with a "slow" powder with a peak pressure of 20ksi. The slower powder is able to supply a usable driving pressure for a longer period of time than the faster powder. Remember, these are dynamic processes, and the peak pressure is a single, instantaneous measurement.
Please explain, because I'm frankly mystified. I kept the example to a straight walled flat ended bullet for simplicity. 3N37 was originally formulated as a .22lr powder, but works nicely in handguns. 4198 is good all round rifle powder, a little fast but works in things like .45-70.
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Attachments
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Re: A quick question regarding HP-38 and W231

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First, recall that I said "Since there are an infinite number of possible combinations of ingredients and particle shape/size that can have the same charge weight and burn rate...". Here (assuming that the curves are correct), we have two powders, 3N37 (a single-base powder) vs. 4198 (a double-base powder) with VERY similar burn rates at very different charge weights in a straight-walled cartridge.

If there are an infinite number with the SAME charge weight, imagine how many more formulas produce identical results when the charge weight is allowed to vary. In this case, we see 3N37 is a single base powder (essentially pure nitrocellulose) with a very open (flaky) structure that burns very fast. 4198 is primarily dinitrotoluene, and the grains have a smooth, shiny surface AND are further retarded (slowed) with a graphite coating. Any two powders could be shown to be capable of producing similar graphs at SOME charge weight and SOME initial conditions.

Since you have QL (or some similar program) I would be very interested in seeing similar curves for the two powders for 30-06 at 70ksi. I would expect the two powders to have VERY different curves.

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