357 mag very inconsistent velocity

[Caliper_Mi]

I've been trying to work a 357 load up for a 6" S&W 66 and have been having problems where my velocity is very erratic. I'm talking ES around 200 for three shots...

Loads have been:
Berrys 158gr FP
1.575" oal
Power Pistol, tried 7.5, 8.0 and 8.5 grain loadings
Blue Dot, tried 8.7, 9.3 and 10 grain loadings
2400, 12gr

Just looking to make 1000-1100 fps for a nice 357 plinking load. The top PP load and 2400 look about there velocity wise if it would just stay consistent. Blue Dot didn't even make it to 900 fps with 10gr when the book claims 1188? But in all of them, the velocity varies so much from shot to shot that I'm not happy. I'm used to seeing ES of 50 or less in my 38spl lead bullet loads without doing anything special, so the 357 loadings are disappointing.

So, what would cause this? They are plated bullets, so no canelure. I'm doing a light roll crimp anyways to be sure the bullets don't move though. I pulled a few seated bullets when starting out and it's not cutting through the plating. All charges are dropped from a Lee measure, but it's the same measure that works fine for Red Dot in 38spl so I have a hard time blaming that.

 

[Schwing]

The first thing I would look at, especially since all the powders are doing it, is my powder drops; are they really consistent? I would hand measure 15 or so and see what variations you are getting. I know you don't think this is the cause but I would still try.

The second thing I would look at would be my crimp. Without crimp grooves or cannelures it is problematic IMO. Is it consistent? For the lighter loads, it doesn't matter as much, but on the heavier end of the load spectrum, a heavy and consistent crimp is necessary to get consistent pressures/velocity.

 

[mdi]

Well, while not an expert with plated bullets (only tried a couple hundred in my 45 ACPs and 9mms), I think I would measure the diameter/weight and check for consistency...

 

[Jlr2267]

I think schwing covered the most likely culprits. Also, is it possible that you mixed up your loaded ammo?

 

[tightgroup tiger]

Can you actually feel a difference in recoil from shot to shot? If you don't, just wondering about your Chrony.

 

[bluetopper]

Them being plated is the culprit. The friction difference in the bore will vary a good bit from bullet to bullet. The stiffer the charge the less this will matter.

 

[ku4hx]

Weigh out say ten charges and then clock those ten. If they all have MV as you expect, suspect the bullets.

 

[gamestalker]

I don't load plated bullets, but I have examined them, and IMO, they are not suited for use with magnum class powders as they relate to revolvers, which is why I don't use them.

Plated bullets don't have a canelure, thus the capability to be consistently crimped. I would venture to guess that without a ways and means to crimp into a canelure with cartridges being fired from a revolver, the amount of bullet pull alone could reach 100% under the right circumstances. Now in some circumstances, such as loading just light target loads, one can probably sustain adequate neck tension to prevent significant bullet pull. But considering the powders being used are in fact magnum class powders, my first thought is that the inertia being created by these stiff loads, is creating inconsistencies that are all over the place.

And I think another contributing factor, is that without a roll crimp into a canelure, we have powders intended for magnum, or close to magnum pressures, being used without any manner of attaining, or sustaining the pressures necessary for a consistent powder burn.

GS

 

[murf]

how much neck tension are you getting with that load? measure diameter of loaded case just below the case mouth, measure diameter of same case just below the base of the seated bullet. the difference is your neck tension. should be 3 to 4 thousanths for that particular load. if it is only 1 thousanth, you are going to have problems with your extreme spreads.

murf

 

[Caliper_Mi]

Ok, did a bunch more measuring...

Throwing .71cc of Power Pistol measured 7.8 or 7.9 gr every time.
Blue Dot was a bit worse as expected. .88cc averaged 9.3gr with a max spread of 9.5-9.1gr.

Grabbed 20 bullets from the box with a max spread from 157.9-158.9gr. Diameters measured mostly .358 with about 1/4 being .3575.

I loaded some rounds, seeing .003-.004 neck tension, I can easily see the bulge where the base of the bullet is. I didn't crimp these, intending to single load them and shoot over the chrono to see if the crimping is at fault. I am using mixed brass, and without a cannelure getting the crimp right has been a bit touchy.

Another question. I'm not really looking for magnum performance, Berrys says to keep their bullets below 1200fps, and I'm only looking for 1000-1100fps. I don't think of this as a stiff load and they feel pretty gentle. Just something a bit warmer than a 38spl load so there is a pleasant level of recoil when I shoot. This seems ideally suited for plated bullets to avoid the mess of cast or the expense of jacketed. Should I be using different powders here? I picked PP and BD powder because the book max was a bit above where I wanted to end up, so it seemed like the right solution...

 

[joneb]

getting the crimp right has been a bit touchy.

It will be impossible with untrimmed brass.

 

[murf]

that .4 grain spread (over 4 percent) with bluedot is not good. i'd look into getting it down to a one tenth grain spread (half a tenth would be better yet).

murf

 

[Steve C]

When looking for a lower velocity load a faster powder has worked better for me than low charges with slow powder. With revolver loads using plated bullets that do not have a crimp groove I usually use a roll crimp over the shoulder of the bullet rather than pushing the crimp into the side of the bullet. This seems to work best for holding the bullets in place to avoid bullet jump due to recoil. This gives a short OAL and less room for powder thus the fast powder.

Sounds like you use Red Dot with your .38 spl loads. Why don't your try it with the .357 mag? Older Alliant data shows 6.0 grs of Red Dot with a 158gr bullet to be the maximum .357 mag load. Start load would be 5.4gr but you should get better results with even lower charges of Red Dot going as low as top level for the .38 spl.

 

[ku4hx]

Blue Dot was a bit worse as expected.

As much as I like Blue Dot, I've relegated it to weighed charges only in certain magnum loadings. Over the decades, BD has always given me powder measure charge weight consistency issues and I finally just moved on. Hand loading for me is a sort of Zen thing anyway, and BD was messing with my Zen.

When I first started with Hercules Blue Dot, it was a choice propellant for certain magnum level loads. But now days, there are just too many other excellent choices for me to get bogged down with it.

 

[ColtPythonElite]

If they are accurate, I wouldn't worry about the spread.

 

[Caliper_Mi]

Sounds like you use Red Dot with your .38 spl loads. Why don't your try it with the .357 mag? Older Alliant data shows 6.0 grs of Red Dot with a 158gr bullet to be the maximum .357 mag load. Start load would be 5.4gr but you should get better results with even lower charges of Red Dot going as low as top level for the .38 spl.

I guess my reloading manuals only list Red Dot with lead bullets. I'll give it a shot though. I found with my 38 that I lose almost 200fps switching from lead to plated, thus I was looking at jacketed bullet data. I've also wondered about something like Unique or 231, but haven't restocked that in my collection lately. I'll also give it a shot seated deeper (of course working up a new totally new charge!) that seems like a good solution and sounds like it should make the crimping go better.

As far as accuracy, I haven't shot this load past 7ish yards, just chrono testing at home before I go load a bunch up. I haven't taken it out to the range yet, but I tend to shoot my handguns on the rifle range as much as I do on the pistol range, so 50-100yd shots are pretty normal which is why I've been worried about the ES on this one.

 

[mongoose33]

In addition to everyone else's ideas, have you checked on differences in powder position in the casing as a possible culprit?

I'll get 100fps or more variance in velocity depending on whether the powder is against the bullet or against the primer. I've had this issue with SR4756 and with 700X. The 4756 is probably not relevant to your powders, but the 700X, as a shotgun powder, may be.

As you load a revolver, the powder is settling against the bullet; after the recoil of the first shot, where is it? You might try a few shots with the powder in both positions and see how much variance you get.

That said, I'd switch to a bullet with a cannelure.

 

[Reefinmike]

Them being plated is the culprit. The friction difference in the bore will vary a good bit from bullet to bullet. The stiffer the charge the less this will matter.

Interesting take on the culprit, I thought you were crazy at first until i looked back at my chrono data taken a while ago. 357 mag- 125gr xtreme- 7.5gr hp38- 1609fps avg velocity(16" bbl)- 117fps spread

Then i look at my powder coated cast 164gr 38 and 357 loads. No more than 25fps spread even in my 2,000 fps magnum loads. I havent bought bullets since i started powdercoating my lead so its no longer an issue

 

[walnut1704]

Try a taper crimp die.

 

[Mad Chemist]

Once you drive that bullet beyond .38+p velocities it needs a stout crimp. A very careful taper crimp might be enough for mild .357loads. For anything approaching normal-full power .357mag, a heavy roll crimp is required. Save the plated bullets for light plinking ammo and get some bullets with a proper crimp groove for the magnum stuff.

 

[joneb]

I've also wondered about something like Unique or 231

I like Unique but like all large flake powders I have tried, they don't meter well in my powder throw.
For loads between 38spl and 357mag with 158gr plated I have had good accuracy with Accurate #5, VV n340 my ES is around 40 fps with plated bullets.
I wonder what the difference in the ES would be if I only used one chamber of the cylinder?
I also use the same head stamp and the brass has been reloaded about the same # of times.

 

[Sunray]

"...tried 7.5, 8.0 and 8.5 grain loadings..." Work up the load from the starting load instead of picking a few and hoping. Pick one powder and work up the load using CAST bullet data for accuracy and forget about the velocity.
And CC's are a metric unit of LIQUID measure. Nothing to do with reloading.
"...Save the plated bullets for light plinking ammo..." That being Caliper_RWVA's plan.

 

[joneb]

using plated bullets that do not have a crimp groove I usually use a roll crimp over the shoulder of the bullet rather than pushing the crimp into the side of the bullet.

I have feed issues with Xtreme's 158gr plated FP in a Rossi lever action, the token cannelure on these bullets is not deep enough to obscure the case mouth. I will experiment with this, the tubular mag. could be a problem though.
Thanks Steve C.

 

[Mad Chemist]

I've been trying to work a 357 load up for a 6" S&W 66 and have been having problems where my velocity is very erratic. I'm talking ES around 200 for three shots...

Loads have been:
Berrys 158gr FP
1.575" oal
Power Pistol, tried 7.5, 8.0 and 8.5 grain loadings
Blue Dot, tried 8.7, 9.3 and 10 grain loadings
2400, 12gr

Just looking to make 1000-1100 fps for a nice 357 plinking load. The top PP load and 2400 look about there velocity wise if it would just stay consistent. Blue Dot didn't even make it to 900 fps with 10gr when the book claims 1188? But in all of them, the velocity varies so much from shot to shot that I'm not happy. I'm used to seeing ES of 50 or less in my 38spl lead bullet loads without doing anything special, so the 357 loadings are disappointing.

So, what would cause this? They are plated bullets, so no canelure. I'm doing a light roll crimp anyways to be sure the bullets don't move though. I pulled a few seated bullets when starting out and it's not cutting through the plating. All charges are dropped from a Lee measure, but it's the same measure that works fine for Red Dot in 38spl so I have a hard time blaming that.

8.5 gr of PP and 10.2gr of Blue dot are max loads for a Speer GD JHP according to Alliant. That is the problem. Either change bullets or substantially reduce the loads.

My max loads of 158gr XTP over Lil gun and H110 barely hit 1350fps from my 4" model 66.

A 158gr plated or lead plinking load from a real 6" barrel (not a universal receiver) should be somewhere around 800-1000fps. Anything over 1100fps in that bullet weight is approaching magnum territory and will require firmer crimp.

 

[ljnowell]

"...tried 7.5, 8.0 and 8.5 grain loadings..." Work up the load from the starting load instead of picking a few and hoping. Pick one powder and work up the load using CAST bullet data for accuracy and forget about the velocity.

And CC's are a metric unit of LIQUID measure. Nothing to do with reloading.

"...Save the plated bullets for light plinking ammo..." That being Caliper_RWVA's plan.

Nothing to do with reloading? Have you EVER read a manual? Powder measures work on volume. The cavities are measured in CC. Why do you think dippers are measured on CC? Why do you think lee disc powders measures have their discs labeled by CC?

Why do you think they have VMDs listed for powders? Do a little more research before you make a statement like that. Especially when you can confuse a guy looking for help.