357 magnum testing question

M

MightyMO1911

New member
So I broke out the chronograph today testing a 357 magnum load. 125 grain jhp with 8 grains of Bullseye powder. They were running along rather well holding an average of 1300 fps. Then, I fired a round and immediately thought something was very wrong. The recoil was much stronger and the velocity jumped to 1500 fps. I am absolutely confident there was an 8 grain charge in the case. No signs of excessive pressure. So I filled the cylinder again. All 6 held the 1300 average. Loaded another cylinder and a couple in, BOOM. Noticeably higher recoil and again the velocity jumped to around 1500 fps.

Ok. Time to stop and evaluate. Those 2 were a different brass. These were chrome federal cases and the others were mixed yellow brass. The inside diameter of the 2 in question was 5 thousandths smaller than the yellow brass. They weighed 7 grains less and held 7 grains less water.

Is this slight reduced case capacity what caused the increased velocity which I assume was because of higher pressure?
 
Something certainly increased the pressure and if you're sure about the powder charge then your other variables are case volume, seating depth, and projectile weight. Sounds like you know for sure there is a case volume difference but I'm not familiar enough with 357 loads to know if that is enough to make that sort of jump. To me that's a major difference but I'm sure others who are more experienced will chime in.
 
Short answer is no. Bullseye builds up pressure fast. It's a great powder for light target loads in a lot of different calibers. Depending on how you're measuring it and what equipment you're loading it on, you could easily be dumping more powder than you think into the case. Having shot the 357mag extensively for almost fifty years, it's been my experience that if you're looking for powders to use in loads other than light target loads, there are several better choices other than Bullseye. What are you loading them on and how are you measuring your powder charges? Do you have other powders to try? I'd pick 2400, 296, 110 ahead of Bullseye if you have access to it.
 
We use a RCBS Uniflo weighed on a RCBS balance scale. I will agree that it is possible that perhaps the loads had 8.1 grains but I would be really, really surprised if it were more than that. Ok. Maybe 8.2 but I just cant see it being more than that. This measure has always thrown quite consistent charges. We do have 296 and Lil Gun. I just cant help but think the case has something to do with it since those were the cases that experienced the change. I shot about 50 of these loads and all but these 2 were fairly consistent, showimg extreme spread of under 50.
 
My best theory about what you are experiencing (if you are DEAD SURE CERTAIN) (for -sure-) about the actual charge inside the case is that the h-u-g-e volume of space you have floating about with a very fast powder charge taking up a small space and a light-for-caliber bullet gives you wide swings depending on exactly where/how the powder is laying around inside the large space. One way you can test this theory is to carefully hold the revolver skyward to "tap" the powder column back toward the case head and carefully cock the hammer when you have slowly leveled the gun back toward the target.

My second best guess is that two totally different pieces of brass gave a wide variance in crimp and that had an effect also that may be combined with the above.

Now, with that said...
Making full bore magnum revolver rounds with fast burning target powder like Bullseye (or AA#2 or Titegroup or Zip or ANY of these fast burning powders) is not a great idea.

Folks tend to make these loads for one of two reasons...
They simply don't realize how different powders of differing burning rates actually WORK inside these cartridges

or

They are attracted to the "less costly" or "less hassle" nature of using one super powder to load dang near everything they ever plan to make.

It's laziness, cheapness or ignorance, or a combo of all three. And if my post sounds very judgmental and it makes me come off a bit obnoxious, I can only say these things:

--sincerely not my intention
--but I don't mind if that happens ;)
--absolutely worth it if it makes even -ONE- handloader stop and say "Hmmm, maybe I should investigate this?!"

Check my posts in this thread for more discussion on my ideas on this subject:
http://thefiringline.com/forums/showthread.php?t=560383

To be clear, I have NO IDEA of the experience or competency level of the OP or anyone who has responded and/or may respond. I post with the idea that it's an open forum with -MANY- folks all along the spectrum who will digest the discussion.

Better powder for 125gr JHP in .357 Magnum?
Too many to list. Ones I happen to use for exactly this are Longshot, 2400, Accurate#9 and Power Pro 300-MP. And there are MANY more and all of them are a better choice than Bullseye.

And Bullseye remains one of my favorite powders ever. But not in full magnum revolver rounds. ;)
 
We use a RCBS Uniflo weighed on a RCBS balance scale. I will agree that it is possible that perhaps the loads had 8.1 grains but I would be really, really surprised if it were more than that. Ok. Maybe 8.2 but I just cant see it being more than that. This measure has always thrown quite consistent charges. We do have 296 and Lil Gun. I just cant help but think the case has something to do with it since those were the cases that experienced the change. I shot about 50 of these loads and all but these 2 were fairly consistent, showimg extreme spread of under 50.
Click to expand...

If you're not weighing every charge, you can easily get an increase of more than 0.1 grains of powder variation. RCBS measures, and most others for that matter, will allow powder to stick in the drop tube on occasion and dump a heavier charge once in a while. You'll also get a lighter one when that happens but it's not as noticeable as the increased charge that follows. You need to get a different powder where there is less pressure variation in heavier loads.
 
Sevens I do not see your post as obnoxious at all. I posted to get inout of those with more knowledge and experience than me. I have been at this a couple of years but have just recently started loading for more than just sending lead down range. I am curious how this all works and correlates and have been nothing short of totally surprised at some of the results. I will read the post you link and hopefully learn what I can. But no, not obnoxious at all. If I ask I should probably be ready for the responses.
 
I'm reluctant to speculate. I'm kind of leaning toward a "propagation variance" of the flame front inside the case, causing a pressure spike. I read Sevens' post kind of fast, and I think that's what he was getting at.

I'm going to be a little more general; but hopefully educational:

One of my legacy 357 loads uses 8.0gn of Bullseye - just like you - except, under a 110 grain bullet ;) I rarely load it these days, as I've moved on to heavier bullets.

Bullseye is a tricky powder in high pressure cartridges. It's much better suited for the low pressure ones like 38 Special and 45 ACP.

When you start driving bullets in what is generally considered magnum type velocities - like 125's going 1300 fps - you are definitely in high pressure territory. And you are working with a very fast powder that prefers to run under pressures around half of where you probably are. I don't prefess to know the complete history of Bullseye; but it was invented in a time when magnum pressures were unheard of in pistols. I think it's fair to say that it's better suited for pressures that were contemporary for its day. And my loading experience agrees.

There's published data that gives sanction to your load recipe (Sierra 5th). But just because it's in a book doesn't mean it's a good course of action. When I want to push a 125 to 1300 fps, I'm reaching for HS-6, Unique, or Power Pistol. My Bullseye will wait for when I go to load 38 Special match target ammo that lumbers along at about 750 fps or so. That's where Bullseye likes to be. As NoSecondBest said:
Bullseye builds up pressure fast. It's a great powder for light target loads in a lot of different calibers.
Click to expand...
 
Interesting but not completely informative. My guess is (yes it is only a guess), that the two rounds in question where from a different reloading secession and had a different powder in them. I don't know about you, but I don't mix nickle plated case with brass cases when I reload. The other thought was what type of primers were you using. Generally I use mag primers for my 357 mag loads, but it is not always necessary for light target loads with fast burning powder.

Defiantly a better choice would have been 2400 powder with a mag primer. 1,500 fps is not un-heard of for a hot 357 round made for a pistol caliber carbine (rifle). But I wouldn't use it in a revolver.

Stay safe and check twice on all reloading secession's.

Jim
 
Last edited:
Well this is just fascinating. I'm not surenif getting a chronograph was a good idea or not (though in this case one wasn't needed. There was obviously a difference) because while I am learning, my list of questions just gets longer and longer. I won't even get into what I saw with a simple primer change today. Good grief.

I really thought I was on the right path with reduced case volume and tighter neck tension because of it being a specific brand/style of case. But it looks like that really didn't have much, if anything to do with it.

Well since it now seems obvious bullseye is a bad powder for this application I won't use it for this again. I did not give any thought to all of the empty space in the case. But I am learning and am grateful to everyone here always so willing to jump in and help out.
 
Small charges of fast burning powder, all the powder up next to the bullet, all the powder next to the primer, or all the powder lying in the bottom of the case from front to back. All these variables will give inconsistent ignition. The flame of the primer "could" ignite all of the powder at once which can cause pressure spikes. I'd suggest a different powder more appropriate for the .357 Magnum. I've read many times that small charges in big long cases, that you should point the barrel upward so the powder falls back to the primer and do it on every shot.
 
My experience is more with rifle's, but differences in brass will change pressure and velocity. I keep all of my brass separated by brand. Once I develop a load with Remington brass, I only use Remington brass for that particular load. Same with Winchester, Hornady, or Federal brass. I might load 308/150's in one brand, 165 Noslers in another, and 165 Hornadys in a 3rd brand of brass.

Federal brass works just fine, but it is known to produce higher pressure and velocity with the same loads compared to those loads in other brass, at least with rifles. As long as I'm working with a mid level load it isn't a problem. But with a load approaching max levels in some brass, you could get an overload in another brand of brass.

I'm usually working with 45-65 gr of powder in rifles vs the 8 gr you are using, but find that I get about the same speeds in Federal brass with 1-1.5 gr less powder. It seems reasonable to me that 200 fps could be a reality here. And it might not be an overload depending on barrel length. 1500 fps would be about right with a 6-8" barrel. From a 4" barrel, that is pushing things.
 
I agree brass causes variances, but he is talking a 17% or more increase in velocity. I use fast burning powders in magnums, although not his powder specifically but have used many a titegroup etc. I have experienced swings of up to 8 at the highest, which I feel is pretty average when using a cheap chrono. I would first assume the chrono was off if I saw a difference like that, but you stated you experienced the massive increase in recoil to go long with it, so we have to assume this is a real problem. I suggest you pull a dozen random rounds and re-weigh and figure out if there is an issue with your charges(equipment). I think the two different kinds of brass giving you such a remarkable increase is more coincidence than cause. Im not the expert since I have never owned your powder, but I have never had quite that spread even using less volume powders than yours. but I would have to hear a random sample of pulled charge weights before speculating further
 
I doubt it is the brass, but I sort by head stamp and trim them to the same length.
What brand of 125gr bullets all the same? Same pimers I assume? I really like to make everything the same when loading high pressure rounds.
 
I've been loading 357 magnum with mixed brass for 30 years. I don't think that's the issue. All of us are relegated to speculation at this point. But what does seem to be a consensus that could be related to the problem, is the powder.

I am a fast powder centric loader. Anybody (if there is anybody) who follows my posts knows this. TFL is loaded with countless posts where somebody is loading with a powder slower than I would for the same application. My recent post about a 10mm load workup with AA7 is a case in point: There have been a couple replies suggesting AA9. Even if I had AA9, it's not likely I would try it for my 10mm guns. After reading posts for a couple years now, I can definitely see that for a given application, I tend to use faster powders than most. The point I'm making is this: if I am telling you your powder is too fast; your powder is too fast ;)

I love Bullseye. It's great stuff. But to me, it has a very specific application: target level rounds. (Bullseye with 45 ACP is a bit of a wild card exception. You can load B'eye with 45 ACP and deliver some pretty decent pop.) What makes Bullseye so darn popular is its ability to ignite so consistently in large volume case (re: 38 Special), in low pressure applications (re: target). It's just really neat that way. When I'm at a pistol competition, chances are excellent that Bullseye is driving my slugs. But when you get into higher velocity applications, Bullseye looses its advantage and other powders are often the better choice.
 
I would have your cylinder chambers checked out by a gunsmith, you could drop the load to 6.5gr and mark the chambers and see if that is the issue.
 
Thanks all for taking time to help out. We dont have many of this particular load left and I've already pulled the several I had of the same brass I had the issue, but I think the smart play would be to pull them all and move on. As Nick stated, the Sierra manual does list this load which is in fact where I got it from, but it is clearly not the best choice. So I will break out the Unique, 296 or find something else.

In just 2 weeks of owning a chronograph and really loading with a purpose other than sending lead down range, I have learned a ton. But, I have at least 10 tons more to learn. I am confident I'll be back here for more help and advice.
 
So I will break out the Unique, 296 or find something else.
Click to expand...

Unique is an excellent choice. Although known for its versatility, even Unique has a wheelhouse where it runs best. And pushing a 125gn bullet in 357 Magnum is right there.
 
8 gr of Bullseye is a max level load in some of my old books. Newer books don't even list it with the 125gr jacketed bullets. AND, while it is a max load by pressure, it is not even close (couple of hundred fps) below the velocity of the max load of slower burning powders.

I don't think you are entirely off base with the difference in case volumes, 7gr of water is, I think a significant amount in a .357 case. But I don't think it is the real culprit in this case, more like a contributing factor.

Clearly what is happening is a pressure spike, and the most likely cause is the position of the powder in the case when fired.

As already mentioned by others, it does make a difference. Under just the right conditions, you get a "detonation" rather then the usual fast burn.

Smokeless powders are "progressive" meaning that they burn at a predetermined rate, and do so as the pressure builds up to the max. But this only works exactly right when the powder is in the proper position. Powder in an on "off normal" position can give off normal results, although it doesn't seem to be predictably consistent how much different it will be.

A load in a reduced capacity case (less volume than the case the load was developed in) will produce higher pressure. Add in the unpredictable powder location because of a small amount of powder in a large case, AND running the pressure at the top end levels (by the amount / type of powder) can give you that "perfect storm" result when all the stars line up just right.

The generally accepted rule is that the "best" powder to use is one that gives the desired velocity, at acceptable pressure, AND fills the case the most.

(assuming acceptable accuracy, as well)

Bullseye is for light to medium loads, Unique for medium to heavy, and 2400 for heavy to max possible. Same thing for other powders, with similar burn rates.

All of them work well in the middle of their ranges. Some of them do weird things at the top and bottom end of those ranges.

IF 1300 is the speed you want, a powder slower than Bullseye would be better.

Not a perfect comparison, but think of this, to get the speed you want, you are redlining the tach in the gear you are in (bullseye) shift to another gear, (different powder) and you drop your RPMs off the red line, and still get the speed...
 
Well, I have to go along with what has been said here with one exception. Alliant says you do not need magnum primers when using #2400 powder and I agree with that statement. Now if you're talking H110/W296 then I agree that magnum primers are needed. But for 2400? No. I've been shooting the .357 Mag. off and on since about 1957, usually with a 158 gr. cast bullet, 2400 powder and standard primer. Been shooting the .357 quite a bit lately as the
.44 has taken a toll on my wrist to some degree.
Can't help you much with loads as I only shoot my own home cast bullets in my handguns. I don't use Bullseye for any load in the .357 Mag.
FWIW, the original load for the .45 ACP was 5.0 gr. of Hercules Bullseye, later changed to the same powder charge and a 230 gr. bullet.
On loads for the .357, originally the load was 15.5 gr. of Hercules 2400. I'd have to buy some current ammo to see if it's anywhere near but I doubt it. I still have one box of .357 Mag. ammo from the 1950's and recoil from those loads is quite stout. Much more than current 158 gr. ammo to be sure. IIRC, current load data for 158 gr. bullets runs about 14.0 gr. of Alliant 2400. Either the original loads were already way too hot or Alliant's version is a bit faster burning. I use a lot of A2400 in my .357 and .44 Magnums and it seems to me that the Alliant version is faster. Still a fine powder for the .357 and .44's.
Paul B.
 
You must log in or register to reply here.
Back
Top