.357 Magnum key-holing in the .357 Maximum?

[oregon45]

So I tried one of my favorite .357 Magnum silhouette loads in my .357 Maximum last week. The load is 6gr of Unique under a 180gr Oregon Trail truncated cone cast bullet in .357 Magnum brass, standard primer. This load has proved very accurate out of my S&W M586 at 100 yards, so I was hoping it would be similarly accurate from my Ruger Super Blackhawk .357 Maximum. No joy:



This was the target at 50 yards. As can be seen the bullets struck sideways. The load responded to elevation adjustments, and I was able to bring the group down into the center of the target but the bullets continued to strike sideways. I discontinued testing after 6 rounds. My Maximum has previously been very accurate with 180gr cast bullets out of .357 Maximum brass, both full out loads and moderate velocity loads, so I'm relatively certain the gun is not the culprit.

Thoughts?

[squawberryman]

Similar to 45ACP in LC cylinder? BIG jump

[cmillard]

that's a bummer. have you tried taking the same load but using it in .357 max brass?

[bradshaw]

oregon45.... your bullets sure are going full flop at 50 yards. As you know, to shoot .357 mag, even .38 Special, in the Maximum is a huge convenience. But, not without accuracy!

Try your soft load in Maximum brass, seating to .357 mag depth. Crimp on or above ogive. Before I tried to put my finger on it, I'd want to look at these dimensions and relationships on you Ruger Maximum:
* forcing cone for smoothness & concentricity. Exceedingly important if forcing cone is deep.
* chamber leade for smooth transition between chamber and throat.
* groove diameter.
* chamber-to-bore alignment (runout).

Here is a .45 Colt comparison I have yet to sort out----two loads, two revolvers:
1) Cast .452 250 RNFP
8 grains Win 231
FC 150
R-P nickel
COL=1.496"
Velocity: FA M83 4-3/4"=942 fps

Accuracy:
FA M83----lousy, starting to keyhole @ 25 yds.
Ruger 03----0.9" @ 25 yds; 4.1" @ 100 yards.



2) Cast 255 SWC
11 grains Hercules Unique
CCI 300
Win brass
COL=1.500"
Velocity: FA M83 4-3/4"=1140 fps
Velocity: Ruger 03 5-1/2"=1130 fps

Accuracy:
FA M83----8" @ 100 yds.
Ruger 03----keyholes at 25 yds.

David Bradshaw