hard to find reliable 357 pressure data

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hard to find reliable 357 pressure data

Postby mtngun » Sun Feb 17, 2008 5:41 pm

I looked for PSI-tested jacketed reload data but didn't find any. It seems most companies are still using CUP for the 357, and their CUP data varies quite a bit, too.

I figured the next best thing would be using Quickload comparisons with several different powders and bullets. Those of you who think that Quickload is always reliable, please note that the 180 TMJ 2400 load was 235 fps slower than what QL predicted.
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The traces for the experimental loads looked way high, and I was sure that the glue holding the strain gage had failed again.
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But the 296 cast traces looked reasonable.
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And my standard Lil Gun loads made perfect traces.
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I am clueless. :(

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Re: hard to find reliable 357 pressure data

Postby mtngun » Sun Feb 17, 2008 7:07 pm

I just autopsied the strain gage. It was stuck on pretty good. Eventually I was able to peel it off but it took some effort. Nothing obviously wrong.

Oh, well. :? I'll try another gage next summer.

I read somewhere that Accurate tried using a piezo for the 357 but got a lot of weird data so they went back to CUP.

Even the published CUP data is not very consistent. Most of the Hodgdon loads top out at 27,000 - 34,000 CUP. Why not run it up to 45,000 CUP? Watcha wanna bet they are experiencing a lot of shot-to-shot measurement variation that forces them to keep the average pressure well below max?

It may be that the small, low pressure cartridges have an inherently inferior signal-to-noise ratio.

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Re: hard to find reliable 357 pressure data

Postby mtngun » Thu Feb 21, 2008 8:17 pm

The question came up on another forum about how much velocity you should get out of a 158 gr. 357 magnum in a rifle. One highly respected reloader says he is getting 2000 fps with Hodgdon's recommended load of 18.0 gr. Lil Gun.

Indeed, Hodgdon claims that Lil Gun produces 14,900 CUP less than H110 when loaded to about the same velocity in the 357 with a 158 gr. Hornady. That sounds too good to be true and you know what they say about things that sound too good to be true. :? Still, I have not tested that particular combination, so I cannot confirm or deny it.

I will point out that Lil Gun did not produce these amazingly low pressures in other cartridges that Hodgdon tested. Are we supposed to believe that the laws of physics are different for the 357 ???????

I will point out that Lil Gun did not produce particularly low pressures in my 357 cast bullet loads -- in fact, when loaded to the same velocity, Lil Gun and WW296 produced about the same pressure, as measured by a strain gage.

I will point out that when Hodgdon or anyone else introdues a new powder, they don't automatically retest all their old powders. In other words, Hodgdon's H110 data may have been tested years before the Lil Gun data. Since they should be recalibrating their pressure barrel every time they use it, it's conceivable that the lower pressure claimed for Lil Gun could be due to a difference in calibration. That makes more sense to me than any other explanation. That's why, when you are doing a comparison test, it's always better to load all the cartridges at the same reloading session and shoot them at the same range session.

I will point out that Hodgdon is still using the obsolete copper crusher method and we don't know how CUP correlates to PSI in the 357 or if it correlates at all. The SAAMI spec is 35,000 PSI or 45,000 CUP, so you would assume that 35,000 PSI = 45,000 CUP, but don't bet on it.

I will point out that Quickload pressures do not agree well with Hodgdon's data or with Winchester's data. Maybe Quickload is wrong, I dunno. The only thing I am sure of is that it is hard to get good pressure data in the 357. :cry:
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Re: hard to find reliable 357 pressure data

Postby mtngun » Fri Feb 22, 2008 7:28 pm

Hodgdon's data for a 357 magnum pistol:

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I wanted to duplicate Hodgdon's data, but I didn't have any 158 gr. Hornady jacketed bullets, so I used my 160 gr. PB revolver bullet instead. I didn't have any H110, so I used WW296 instead. And I didn't have a CUP gun, so I used a strain gage on my Marlin 1894 instead.

Since I have no scientific way to calibrate the strain gage on this gun, my pressure data should only be used for comparing one load to the next. I'm pretty sure that the actual pressures are higher than the pressures indicated by this strain gage, so don't interpret this data as a green light to hot load your 357. Some of the powder charges are deliberate overloads, so don't try to duplicate them.

Here's the Lil Gun data:
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And here's the WW296 data. I should have tried a greater range of powder charges, but I didn't have enough empty cases (do as I say, not as I do).
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Sorry, I couldn't figure out how to get my spreadsheet to dispaly the linear regression numbers, but you can look at the chart and see that both powders need about 33,500 psi (and remember, that's not calibrated :!:) to hit 2000 fps. I believe Hodgdon's data is a mile off.

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Re: hard to find reliable 357 pressure data

Postby mtngun » Fri Feb 22, 2008 7:34 pm

Here's one of the pressure curves:
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T1 = 2036 fps (highest velocitiy and highest pressure)
T2 = 2008 fps
T3 = 2009 fps

T5 = 1971 fps (lowest velocity and lowest pressure on this trace)
T6 = 2016 fps
T7 = 2001 fps

As you can see, the shape of the Lil Gun curves is just the same as the shape of the WW296 curves (in order to achieve the same velocity at amazingly low pressures, as Hodgdon claims, Lil Gun's pressure curve would have to have an amazingly different shape).

I forgot to mention that this was the first outing with a new (actually reconditioned, $50, direct from the manufacturer) Chrony chronograph. My usual Competition Electronics chronograph is being repaired. The Chrony seems to give higher velocities than my old chrono. When I get the old chrono back, I'll do a comparison test.

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Re: hard to find reliable 357 pressure data

Postby mtngun » Sat Feb 23, 2008 7:49 pm

this poster's name has been lost:

I thought I'd offer my experiences with Lil'Gun in a .357 lever action. Although I have a Rossi with a 24" bbl.

I've been using Lil' Gun with good success in cast bullets and moderate success with paper patched bullets. My favorite load is 13 grains of Lil' Gun and a 158 grain cast bullet. The velocity is somewhere around 1500 fps from the 24" bbl, and can produce a 1" group at 40 meters (open sights). This load is also excellent in my Blackhawk Revolver. The bullet is from a Lee 158 grain roundnose-flatpoint mold, bevel base, no check, straight wheel weights and softened in an oven. I know, I know, but this is before I even heard of Mountain Molds; you can actually thank Lee for without them I probably wouldn't have even gotten into casting, and hence never ordered from you.

I use the SAME bullet for paper patch (I plan on ordering one from you specifically for this task), but I cast with plumbers lead and run it through a .358 sizer after patching. For paper patched loads I run it on up to 17.4 grains of Lil'Gun and get about 3-4" groups at 100 yards.

I also have a Lyman 195 grain roundnose mold. Using straight wheel weights I get good performance from my Blackhawk with charges anywhere from 12 to 13 grains of Lil' Gun. I'm not happy with the way this bullet works in my Rossi Lever Action, I suspect the twist rate is too slow.

I too was baffled by the very low pressures reported by Hodgdon. In fact I literally telephoned them to confirm that this was not an error. They said this was in fact their true measurements. I still regard this as suspect because the primers on my paper-patched and 195 grain loads are severely flattened tophatted in fact. I don't know if this is common, but I've learned to ignore the tophatting primers since I see this all the time with factory loads also. Nevertheless, it does indicate that the pressures are up there. I have no clue whether primers should top hat at 25,000 CUP or not.

Well I decided to load some rounds to the exact specs in the Hodgon manual. So I ordered some Hornady 158 grain XTPs, brand new Winchester cases, and WSPM primers. I used 18 grains of Lil' Gun and whatever the OAL they listed in the manual. Sure enough, primers were severely flattened. Accuracy was good enough to kill deer with so I decided to use this for hunting.

Now, since Lil'Gun is intended for 410 shotguns, I thought maybe other company's 410 powders might be suitable for pistols. I asked Alliant about their 410 powder and they would not recommend it for use in metallic cartridges. The reason they gave was because as temperatures cooled down, pressures increased. They said that in their testing they got similar low pressures as Lil'Gun and that it took severely cold temperatures (tens of degrees below zero) to get the pressure to exceed SAAMI. The guy said they tested Lil'Gun and found that Lil' Gun also increased pressures as it got colder. Although it took severe cold temps to produce pressures that exceeded SAAMI in their tests, Alliant just wasn't willing to take the risk to publish load data for metallic cartridges.

Over the course of a few years of using Lil' Gun, I can attest to it's temperature sensitivity. On days when the temps were in the high 80's and 90's I would occasionally get squibs in the revolver (I initially thought this was due to the lube melting). On normal summer temps, I would see lots of unburnt powder in the revolver. And in cool fall and cold winter temps the powder would burn completely. I never had problems in the Lever Action and I assume this is because there is no pressure loss from a cylinder gap.

Then just this last November I had an alarming experience. Normally I would always use factory loads for deer hunting, but since I purchased the XTP's and had brand new cases and what I considered to be reliable reloads I opted to go with the reloads. On the second day of the season I was pursuing a deer another member of my hunting party wounded. I jumped him and took a shot. I continued pursuit and when I came up on him again, my gun wouldn't fire. Later my gun completely jammed. At home I dismantled it and found a tiny piece of primer jamming the works! Yes the primer perforated.

This was November in Wisconsin and we had snow, but the temperatures were well above zero. The round was in the chamber for several hours so it had plenty of time to cool down to ambient temps. This was the 18 grains of Lil' Gun, new Winchester cases, and 158 grain XTP load that supposedly generated a pip-squeaky 25,000 CUP and it blew a hole in the primer!

So now I'll have to re-think the use of Lil' Gun.

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Re: hard to find reliable 357 pressure data

Postby mtngun » Sat Feb 23, 2008 7:55 pm

That is interesting to hear that Alliant tested Lil Gun.

I haven't noticed any cold weather problems myself but then I rarely shoot in cold weather.

I wasn't looking over Hodgdon's shoulder when they did their Lil Gun tests so I don't know what went wrong but the 25,000 psi load defies the laws of physics. If I were the boss at Hodgdon, I would have them retest it and especially test H110 at the same time. That would answer a lot of questions.

Mark my word, the day will come when Hodgdon recalls that data and someone at Hodgdon is going to have a lot of explaining to do, probably while they are standing in the unemployment line.

Regarding the pierced primers and flattened primers, that is very common in lever guns even with some mild loads. Excess headspace can cause flattened primers even with mild loads, and it is very common for lever guns to have sloppy headspace. It is harmless for the most part.

The pierced primers are due to the firing pin being a sloppy fit in the firing pin hole, allowing the primer metal to flow back into the hole.

My Marlin will pierce primers with some reduced loads but not with max loads.

If you had a gunsmith bush the firing pin, that would probably eliminate the pierced primers. McPherson describes the procedure in his book Accurizing the Factory Rifle.

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Re: hard to find reliable 357 pressure data

Postby mtngun » Thu Feb 28, 2008 7:34 pm

I have ranted about Hodgdon's 357 data before. Some of their data makes no sense whatsoever. Anyone with half a brain can glance at the Hodgdon data and tell something is wrong.

The sad thing is that Hodgdon bought out Winchester Powder. WW296 is my favorite pistol powder, or at least, it was before Hodgdon took over. Winchester used to publish some good PSI data for the 357.

I just visited the Winchester web site and the good 357 PSI data is no longer there. In its place is the screwed-up Hodgdon CUP data.

Take a look at this and see if anything seems suspicious.
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Am I the only one who wonders why the rifle barrel was 15 fps SLOWER than the pistol barrel(s)? Am I the only one who suspects that maybe, just maybe, possibly, conceivably -- someone SCREWED UP?

Am I the only one who thinks it is amazing that this load gave EXACTLY the same pressure in three different test barrels? I mean, you would expect that there would be a couple thousand PSI difference, due to normal variations in dimensions, temperature, components, and calibration. But no, we are supposed to believe that all three barrels gave exactly 39,100 CUP. Not 39,099, not 39,101, but 39,100. :roll:

And last but not least, am I the only one who wonders why Hodgdon is still using the obsolete CUP system? Actually, the answer to that question is simple -- new pressure barrels are very expensive.

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Re: hard to find reliable 357 pressure data

Postby mtngun » Thu Jan 05, 2017 3:16 pm

Bumping this up because I finally fixed the broken data tables, and the subject of 357 load data came up again today.


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