357 mag bullet movement


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floydster
March 11, 2012, 05:59 PM
Hi all, I am using Berry's 158 gr. plated bullets in my newly acquired Security Six, as you can see I am having probs with the bullet moving outward.
I have good bullet tension and roll crimp, I don't think I can crimp anymore without cutting into the plating.
The load I am using is 6 gr. Bullseye--it is a very accurate load in both my 357 Blackhawk and the Sec. Six, and I don't have this problem using this load in the Blackhawk.
Any advice would be appreciated:)
Floydster

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Waywatcher
March 11, 2012, 06:22 PM
That looks like adequate crimp; I would look at your expander or your resizer.

Either the brass is not getting resized enough, or the expander is expanding too much; and the result is you have insufficient tension of the brass holding onto the bullet.

When I seat bullets, you can ever-so-slightly see where the bullet ends.

Lost Sheep
March 11, 2012, 07:44 PM
Yes, what waywatcher said.

Measure the diameter of the bullet, the inside diameter of the case both before and after expanding the case mouth. If you can't reliably measure the inside diameter, measure the outside diameter and subtract the case wall thickness. Measure the diameter of the fired case both before and after resizing, too. All measurements should be taken at the same temperature.

I am told that most of the bullet pull force (retention) is supplied by friction with the case walls. The retention added by the crimp is only part of the story. This is even more important with semi-autos than with revolvers because they have no (or very little) crimp at the mouth.

The reason it happens with your SS and not your Blackhawk, I surmise, is that the phenomon is more pronounced in lighter guns. Their lack of mass (and thus, inertia) makes the backwards acceleration greater, thus giving the bullets in the unfired chambers a bigger kick. This is called "jumping crimp" and was a real problem for Craig Medred (Anchorage Daily News Outdoors Writer) in the late '70s when he took a Grizzly Bear with his 454 Casull and wound up with his revolver tied up with a bullet nose protruding from the front of the cylinder.

I suspect that if you increase the powder charge, it will happen in your BH, too, just so your SS won't feel lonely.

If the sizing die is not reducing the diameter of the case to the point where it is impossible to start a bullet in the case without belling, I suspect your sizing die is oversized or worn out. I mention this because there is no visible expansion of the case wall where the base of the bullet is. Usually there is a discernable difference.

Good Luck.

Lost Sheep

rcmodel
March 11, 2012, 07:51 PM
+1

6.0 Bullseye/158 is getting right up there.

Your expander should be at least .002" smaller then bullet dia, and .003" won't hurt.

If all else fails, seat deeper and roll-crimp over the ogive shoulder.

Might want to back off the Bullseye a little if you do that though.

rc

Walkalong
March 11, 2012, 08:12 PM
I agree that you need more neck tension. I would also add that I believe a heavy taper crimp (http://www.thehighroad.org/showpost.php?p=5942202&postcount=37) would serve you better than that light roll crimp on a plated bullet.

357 Terms
March 11, 2012, 08:24 PM
+1 on a taper crimp on a bullet with no cannelure.

ArchAngelCD
March 11, 2012, 10:20 PM
I agree that you need more neck tension. I would also add that I believe a heavy taper crimp (http://www.thehighroad.org/showpost.php?p=5942202&postcount=37) would serve you better than that light roll crimp on a plated bullet.
This is good advice, I agree... I bought a .38 taper crimp die for this and loading Speer shot caplets.

floydster
March 12, 2012, 09:13 AM
Thanks guys for the replys.
Looks like I will have to get a taper crimp die.
After sizing, my inside case is .355 and the bullet is .357, when I push the round on the edge of the bench after seating the bullet( without a roll crimp) I can't push the bullet in the case farther, and I am pushing hard.
I don't have this prob with my cast bullets which I size to .358.
Thanks again, Floydster

Blue68f100
March 12, 2012, 09:33 AM
All the taper crimp die is for is to remove the belling/expanding. Neck tension is brass to bullet fit. Since Berry's normally run slightly over size I would suspect the expander is too large but not by much.

Walkalong
March 12, 2012, 10:36 AM
You are thinking of an auto case that headspaces on the case mouth. With revolver cases you can taper crimp as heavy as the bullet can take and still shoot well.

beatledog7
March 12, 2012, 12:14 PM
Neck tension is probably the culprit. Either sizing die is not squeezing cases down enough or flaring insert is opening them too much.

There is another possibility. Too much taper crimp can sometimes squeeze the bullet, which is inelastic. The case mouth is more elastic, and springs back, loosening the fit.

Maybe another possibility, but I'm out on a limb here. A slower powder would give these bullets more of a gradual push than a sudden jolt. Something like 2400 might be a better powder choice for bullets with no cannelure.

918v
March 12, 2012, 12:24 PM
Or the bullet in sundersized. I like to crimp these over the shoulder. That way the case mouth has something to grip. Digging the case mouth into the side of the bullet does nothing, as you can see. Crimping over the shoulder creates a shorter OAL and the load should be adjusted.

GP100man
March 12, 2012, 08:19 PM
Is that WW brass ??? maybe change brand of brass , summtin with a little thicker neck ???

WW brass is the only kind I have jumpin problems with . Tried the plated stuff ,but gave up on it .

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