Help .357mag Overpressure signs?

[Blakenzy]

So I am loading .357mag for a S&W 686-6+.

Using Win231 and powder coated 158gr RN bullets sized at .358, win. SP primers. Cases are mostly Aguila nickle plated, some Federal, few Winchester.

Load is 6.0gr of powder with a cartridge length of 1.590 (Lee load data states min 6.2gr/ max 6.7, Min OAL 1.540). Crimped in crimp canelure with a FCD.

Seems like a mild load, except that after examining 21 cases fired, 7-10 show some degree of primer flattening (from slight to overt) and some have very slight firing pin indent cratering, barely. The rest seem to be just fine, nice round shoulders. No loose primers. I noticed a significantly louder report and more blast from a couple (loudness prompted me to pop cylinder open and look ). Some had stickyer extraction than others but nothing extreme.

Was running a chrono and got an average of 1030fps, with a low end of 994fps which happened to be one of the loud ones.

So I stopped shooting after the third cylinder and pulled the remaining 23 cartridges I had loaded with an inertial hammer trying not to lose any of the power and weighed each one. Did not find a single load over 6.0. If my powder measure was at fault and dispensing erratically I think it would show in the other half of unfired cartridges. There is alway the chance of having double charged but I think that would have been more catastrophic-like.

Case length of fired cartridges are all about 1.280-1.285. There is nothing unsual about the gun that I can see. Cylinder throats do not seem to be overly tight and the gun was clean, all cartridges chambered freely.

What can be going wrong here?

 

[Walkalong]

Need to see some primer pics. Lead I assume since you mentioned sizing.

From Hodgdon online.

158 GR. CAST LSWC
Starting Loads
Maximum Loads
Manufacturer
Powder
Bullet Diam.
C.O.L.
Grs.
Vel. (ft/s)
Pressure
Grs.
Vel. (ft/s)
Pressure
Winchester
231
.358"
1.610"
3.4
796
12,600 CUP
5.0
1,109
23,900 CUP

 

[243winxb]

low end of 994fps which happened to be one of the loud ones.

I dont see anything that stands out as a major problem. Having not used 231 powder or coated bullets, i would guess . - Powder position may be a factor on the velocity?

 

[Blakenzy]

Powder position may be a factor on the velocity?

I was considering that and did dip the muzzle down on some and then up on others. Didn´t notice a trend.

 

[627PCFan]

You have a mix match and I had the same problems in 45ACP a few years ago. The Aguila primers look sharper, everything else is round and of no concern except for the random winchester, 2nd row, 3rd from the right.

Ditch the aguila.
I learned my lesson, I dont shot mixed brass anymore

 

[243winxb]

The 2 on the bottom right look very different to me. I covered the correct primers before for the 357 mag. Imo. Magnum is what i use. https://www.thehighroad.org/index.php?threads/357-magnum-primer-question.590545/

 

[Tracker57]

Max load is 5.0

 

[Blakenzy]

Tracker57, the Lee second edition manual does indeed mention 6.2 of 231 as a starting load for 158gr lead. I just quadruple checked now. Maybe it's a misprint?

 

[labnoti]

Primer flattening is an unreliable sign. I loaded .38 Special cases to 6.4 grains with 158 grain plated bullets. I think that was near the limit, and it didn't work well for me, so I've gone back to 6.0 grains at 1.480 OAL. Those would be a lot higher pressure than 1.590".

None of this is from published loads, so take it as is and use at your own risk:
from Quick Load
W231
158 gr. Rainier Plated HP
.38 SPC at 1.480", 6.0 gr = 27556 psi, 5 shot mean velocity=921fps, SD=9fps, 2.125" barrel
.38 SPC at 1.480", 6.4 gr = 31195 psi, 5 shot mean velocity=901fps, SD=11fps, , 2.125" barrel (recommend against this)
.357 at 1.590", 6.0 gr = 24267 psi (calculated only)
.357 at 1.590", 6.4 gr = 27381 psi (calculated only)

With all that said, I suggest a slower powder for .357/158gr. Something like Longshot or H110. I tried HP38/W231 experimentally because I had it for .38/125gr. where it works well. I don't like the results I got with it for 158gr. I got much better results with Longshot and H110. I'm going to work on IMR4227 next.

From the sticky at the top of reloading. Required warning.

CAUTION: The following post includes loading data beyond currently published maximums for this cartridge. USE AT YOUR OWN RISK. Neither the writer, The High Road, nor the staff of THR assume any liability for any damage or injury resulting from use of this information.

 

[243winxb]

I saw the Hodgdon 5 gr maximun fot 231, before Walkalong posted it.

powder coated 158gr RN

Online, i see claims that coated bullets can handle pressure, velocity better? So i didnt post it.

231 is a faster burn rate powder then i would use with a 158 gr lswc. Alliants 2400 @13 gr is my choice for the 357 magnum. Slower burn rate.

Edit add- W231 is a flattened ball powder. Imo, ball powders need a mag primer and should almost fill the case.

 

[labnoti]

The 5.0 gr. maximum is also listed at 23,900 CUP. That's well below over-pressure conditions in a .357 magnum, and the question was about overpressure, not leading or other issues. Those other issues are going to be dependent on the velocity achieved in the barrel length used. The bullet manufacture should specify a maximum velocity, but for soft cast lead bullets, a general rule of thumb is around 1100fps (and that's where Hodgdon limited their LSWC load). I shoot plated bullets the manufacturer claims to have a maximum of 1250fps (they make other bullets suitable for other velocities). Plated and PC bullets should have a higher maximum velocity before fouling than soft-cast lead. For me, a short barrel limits velocity to under 1000fps anyway.

With respect to pressure, copper-jacketed and solid copper bullets are going to have a higher initial start pressure than lead, plated or PC bullets. The softer lead, plated and PC bullets are not likely to cause higher pressure behind them than a jacketed bullet unless they're oversize. The OP should check their coated bullets are the expected diameter, but I doubt that's the issue.

 

[Blakenzy]

The bullets are a uniform .358 in all bullets measured.

Ok leaving aside judgement of correct charge weight, assuming powder charges were consistently charged (or overcharged), what would cause differences in the primers? Some are quite flattened and sharp and others are well round, totally different even among cases of the same headstamp (those two Aguilas on the bottom right corner for example). They seem to be all over the place.

 

[ArchAngelCD]

This is why trying to read primers is a bad way to judge pressure, it's just no reliable.

You want to see flattened primers that look like they are way over pressure? Shoot some factory Winchester .357 Magnum ammo and be amazed.

When using primers as a pressure guide you should use that info in conjunction with others signs but not alone IMO.

As for Hodgdon stopping at 5.0gr W231, that is done to prevent leading, not for pressure. Another example, look at the 158gr cast .357 load using HS-6. They stop at 7.0gr HS-6 with a reporter pressure of only 15,500 CUP. That pressure isn't close to the .38 Special max let alone the .357 Magnum. It's done to prevent leading and verified by Hodgdon.

 

[labnoti]

I don't fully understand why primers sometimes flow into the cup rim and sometimes don't. But this is what I think happens when a cartridge in a revolver is fired.

Before primer ignition, the cartridge is sitting a bit loose in the chamber. It was sized to slide into the chamber easily, and there's sufficient excess headspace that the cylinder would certainly close with the cartridge in the chamber. The cartridge could be slid all the way back against the recoil shield or it could be slid foward however much space is provided given the headspace for that chamber and the thickness of that case's rim. It could also be in some position in-between.

When the primer ignites, pressure begins to build inside the case and the cartridge's components are driven apart. The desired effect of the bullet being driven forward is happening, but the case is also being pressed against the chamber walls and the head is being thrust back toward the recoil shield.

We want the chambers and brass case to be clean, polished, and slick so the case walls don't stick to the chamber which would force the case to stretch until the head touched the recoil sheild. Instead, we want the case to slide back. But remember that some cases will slide farther than others depending on where they were when the pressure began.

A gun with excessive headspace will certainly cause cases to slam back against the recoil shield. I suspect that guns with normal headspace will still have some variance in how much a case is accelerated before it hits the recoil shield. There are other variables as well, such as the tightness of the primer in the pocket, and the hardness of the cup. And there is the variable of how much pressure is formed in the case. All these variables are reasons why we might see differences in primer cup deformation. I think there may be even more having to do with how the firing pin responds to reactive forces to its strike.

Because I don't find primer cup deformation very informative with regard to pressure, I mostly disregard it when it is a single sign and consider other signs more informative. I certainly make loads that are not book loads, but I have multiple safeguards to keep myself from loading something that will be overpressure. As much as I experiment, I don't load anything overpressure. Guys like Elmer Keith loaded stuff that was way overpressure. While I don't follow book loads, I don't do anything like what Keith and others were doing. Because of that, I don't expect to see signs of overpressure ever. It isn't something that I flirt with at all.

Overpressure conditions in a revolver or handgun may show no signs whatsoever. Because some of the guns' pressure limits are so low, the cases, primers and so on just won't show anything. They'd have to be engineered to be pathetically weak to do so.

Using a gun the performance of which is familiar to me and which I know to be excellent, I would be concerned if I noticed excessive recoil, or cases sticking when I know what to expect for recoil and that cases don't normally stick in that gun. But mostly, I make sure my cartridges are under the gun's standard pressure limits before I fire them. I typically have a margin under the standard limits, and then there is a margin from there to the proof limits.

 

[greg_r]

As noted above primers are not a reliable means to judge pressure. Actually it's very hard to detect pressure signs by looking at a straight walled revolver case that headspaces on the rim. Likely the first sign of excessive pressure is the revolver disassembling itself. Sticky extraction is something to watch for.

Labnoti did a pretty good job explaining it I think.

 

[buck460XVR]

Chrono results tell me you should be fine....not excessive velocity. Flattened primers mean little in magnum revolvers, but sticky extraction tell me I may be at the upper limits of what my gun wants.(if chambers are clean and smooth).

 

[GP100man]

WW 231 has a very sharp pressure curve , it burns qwik compared to say 2400 which has a longer curve , it burns the whole length of the barrel & then some, making more fps at a lower & longer pressure curve.

One thing to consider when loading lead bullets is the length of the bearing surface or body of the bullet below the crimp.
231 when workin at the top ranges gets VERY sensitive to this .

As far as powder position , try this , point the muzzle down & chrono 5-10 shots then point muzzle up & chrono 5-10 shots & see what happens , point muzzle to settle powder into position after each shot.

Primers are not a reliable as each batch of material the manufacturers get to construct primers with isn't the same, close but different. I`m sure they test each batch some way.
I have no problems with any of the primers in the pic, they did their job, ignited & kept the pressure in front of em.

The PROBLEM I have is you said some were" stickeyer" on extraction & the mixed brass.
Stickyness in 357 means you are approaching the limits of the cases to retract from the cyl walls & should back off on pressure.

Different manufactures of brass case while outside diminsions are the same ,inside volumes vary greatly , especially workin at top pressures, this also may be causing your different muzzle report.

WW231 is a great powder & it works very well just not in 1k fps 357 mag loads .

Enuff for now .

GP

 

[Walkalong]

The 5.0 gr. maximum is also listed at 23,900 CUP. That's well below over-pressure conditions in a .357 magnum, and the question was about overpressure,

True, but we don't know if they just stopped there, or pressures built very quickly and/or erratically above that.

 

[Walkalong]

Primers will lie to you sometimes, but when you get very flattened primers, it is a good idea to take note. A couple of those would concern me.

GP100man gave some good advise.

Try the powder forward vs powder back test, sometimes the results can be eye opening.

 

[243winxb]

I noticed a significantly louder report and more blast from a couple (loudness

with a low end of 994fps which happened to be one of the loud ones.

Do the jump crimp test. Fire all but the last round in the cylinder. Has the bullet moved forward out of the case? Compare OAL before and after.
Mixed brass will produce different bullet hold.

Nickel cases, as they gets used a lot, will stick before brass of the same manufacture. Measurement showed less spring back of nickel on firing. Sizing diameters were the same.

I do read primers. Yours tell me the 231 ball powder, in the big case is producing different pressures.

I have use W296, 4227, Unique and 2400 in the 357 mag, with 158gr lswc. The magmum primer has a thicker cup, so i use it. No more pierced primers.

 

[Blue68f100]

Another thing that has not been mentioned when it comes to reading primers is the size of the flash hole. The smaller the hole the less pressure the primers see, larger holes see more pressure sooner. Think of the flash hole as a choke. Over size in not good. The reason if your shooting just a primer no powder they back out if you do not enlarge the flash hole.

Primers in general are not a reliable source for reading pressure. It needs to be used with other indicators.

 

[mcb]

More thoughts. Primers are an OK pressure indicator on rifle cartridges that are running 55-65ksi. If you have flat sharp corner or even mushroom shaped primers or cratered indents coming out of rifle cases you might have a pressure issue. Again that sign alone is not sufficient but more reliable in a rifle. In pistol cartridges that have a peak operating pressures of ~35ksi, then primer pressure indication, by the time its legitimately showing up, your likely blowing up the revolver. Also revolvers can create artificially flat primers. If the primer backs out out of the case due to loose primer pockets, small flash holes (or a combination of said same) and then as the powder ignites the case is slams back against the recoil shield re-seating the primer this can create very flat even mushroom shaped primers while still having chamber pressures well within safe limits.

 

[possumbelly220]

One other thing you might want to look at, was the brass trimmed before loading? I have found that using mixed brass will produce all kinds of crimps, from light to very heavy and this could lead to pressure spikes. Anytime I load a new batch of mixed brass I always trim it.

 

[Buck13]

Try switching to a slightly slower powder (picking a load that you expect to give the same velocity) and see if that changes the result? If it's the brass/cylinder/primer fit being erratic, there should probably be little change. If it's peakiness of 231, primers should become uniform and non-flattened. Universal, Unique, Power Pistol, AA#5 or #7, CFE Pistol, Longshot...? I'd probably start with 5.5 grains of Universal. If you're worried that would be too mild, 7.0 grains of Longshot.

 

[Steve C]

As others have said, the primers look OK. I only know I'm reaching high pressures when I see cratered, extreme flattening or pierced primers. Below is what I would considered a truly flattened primer in a .357 mag case that was a range pick up.