Pressure calculating software?

[bozhoz]

I noticed in some posts that it appears there is some software out there that can calculate the anticipated pressure from a particular reload? Is there anyone out there with that software that can tell me the pressure on this particular round?

Caliber: 9mm Luger
Case: Winchester
Primer: WSP
Powder: 6.2 grains IMR SR-4756
Bullet: Winchester 115gr FMJ RN- Hollow Base
OAL: 1.10"

Shot out of a Glock 19

This load lists as under maximum in the Hornady manual, but appears to be way OVER max based on the IMR Reloading Data Center. I am a little nervous to shoot them, although 6.0 grains shot just fine. Better safe than sorry.

[ZeSpectre]

The problem with this is that pressure behavior is not really very consistent as you increase the powder charge.

For example, .40 S&W loads are known to follow a fairly predictable curve, but there are a couple of places where pressure "spikes" higher than it should given the formula so anything that just calculates on a curve or line isn't going to work.

[Sevens]

I have NO IDEA about your load data, since I've never used that powder, but I'll make a comment in general.

You are talking about 0.2 grain increase in powder.

If it's a real, serious problem, then you probably didn't do a very thorough examination of the 6.0 grain load when you say that it shot just fine.

If you are seeing pressure signs at 6.0 grains, then 6.2 is a problem.
If you are certain that you are seeing NO signs of high pressure at 6.0 grains, I wouldn't think that 6.2 grains is going to be nuclear.

[bozhoz]

That makes perfect sense... I was under the impression that the software was a collection of actual datapoints that should give a reasonable idea of what to expect.

[Sevens]

The program you are looking for is called QuickLoad.
It's expensive ($150 I think?) and it's very powerful, but you also have to know what you are doing to make it work. There are many variables that need answers to get accurate results.

I'd like to have the software myself, but it's more than I'd be willing to spend for something that I'm likely not intelligent enough to use properly!

[FlyFish]

Part of the discrepancy might be that you're not duplicating the load exactly. For example, although I don't have their manual in front of me, I doubt that Hornady provides load data for Winchester bullets. Similar changes in components (e.g., different brands of cases have different internal volume, some primers are hotter than others) can change maximum pressure. Unless you're using all of the components of a load recipe exactly as listed (and even if you are, because of differences among firearms and other factors) it's only a general guide and should be used accordingly, i.e. worked up to slowly and carefully.

[SL1]

QuickLOAD does not have the Winchester 115 grain hollow-base RNFMJ bullet, nor IMR SR-4756 powder in its database. SO, you will not get much help there. Homer Powley did produce a correlation for pressure vs velocity measurements, but it assumes the OPTIMUM powder was used and is really only applicable to rifle cartridges so far as the data was taken only from rifles. SO, using that would be a significant extrapolation for the correlation, and MIGHT be pretty inaccurate. Nothing else that I know about is going to be accurate enough to say that 6.0 vs 6.2 grains is below and above the SAAMI pressure limit.

One point to consider is that the various 9mm Luger bullets have a lot of different shapes, which change the powder space available with the same seating depth. So, it does not surprise me that the max charge data for 2 different bullets differs by a substantial amount. Also, I looked for the SR-4756 data on Hodgdon's website, and only found data for 115 gr LEAD RN bullets. So that is really apples-to-oranges if that is the data you are referring to.

Hodgdon's 2008 annual reloading manual magazine list 6.3 grains of SR-4756 as a compressed load with a 115 grain Remington JHP. The fact that it is a compressed load gives some indication THAT particular bullet shape provides pretty small case capacity for a 115 grain bullet at its stated COL, which is 1.110". So, unless you really compress the powder a lot with your Winchester 115 grain bullet, I doubt you would exceed the conditions of that published load by much. Its published pressure is 30,600 CUP. That isn't easy to relate to current data in PSI, but it is below the old SAAMI CUP standard, which is listed as 33,000 CUP in newer manuals and 35,700 CUP in some of the manuals that are as old as this data. It is really old data, copied verbatim by Hodgdon from old Dupont publications from the 1980s (and maybe earlier).

So, my guess is that 6.2 grains is not going to be a problem. But, don't sue me if it is - - you take the risk. All I can do is tell you what information is out there.

With respect to "working-up" loads for handguns, most of the pressure signs that folks say to look for are not going to show-up until you are WAY over typical handgun pressure limits. Brass cases work well up into the 60,000 psi range, so don't expect to see breach-face marks on the case heads at 35,000 or 40,000 psi. Primers are designed to work in high-pressure cartridges, too. With SOFT primers, you MIGHT see some differences as you exceed 35,000 psi, but that is not reliable, because primers differ too much, even lot-to-lot with the same brand. In an autoloader, you MIGHT get some indication from how your cases eject, compared to factory loads. But, that assumes you are using full-power loads with near-optimum powder types and the same weight bullets. If the handloaded cases are being thrown farther and harder, that is a sign that you are stressing things more. But, it is possible to get very hign pressures by using very fast powders, and still not be ejecting cases with unusually high force.

So, stick with published maximums and think carefully about component substitutions. Those are the things that are best at keeping you out of trouble. But, keep looking for pressure signs, too. They can help you detect situations where excessive pressures are occurring BEFORE the gun or case blows apart with a FEW shots. Like when your bulelts are being set back during the feed cycle and seriously raising pressure. The pressure signs just can't be used to keep pressures safely near the top of the proper working range. If you shoot a lot of excessively hot rounds in a pistol, it will eventually fail due to metal fatigue, so you want to keep an eye out for pressure problems at all times and catch them as soon as they appear.

SL1

[bozhoz]

Thanks SL1 that was an outstanding explanation.

[Don P]

Lee's reloading manual has a very indept explanation of pressure's. It explains how to figure it out. Cheap program: calculator,pencil, paper