Home Forums Hunting & Shooting Ask The Gunwriters COW in a large case?

Personally, I don't like the COW method. I formed some cases for my 6.5-06 AI with COW just for the convenience of being able to fire the rounds in my garage. Got some case separations, not at the head but at the shoulder of the .25-06 brass I was using (not the new shoulder), all the way around the case.

The virgin brass had the slight crush fit it's supposed to have in an AI chamber and I had a gunsmith double-check the headspace, it was perfect.

Never had any case separations shooting fire-forming loads.

I had the same thing happen with some new .338 Winchester Magnum brass, when it was fired in a standard .338 WM chamber. Turned out that batch of brass was badly annealed.

Have never had anything like it happen with the COW method.

That could've been part of the problem, but once I saw those cases separate I unloaded the rest of the COW rounds and had no separations with the normal FF rounds. Same brass.

Interesting!

What brand of brass?

It was Norma .270 brass.

I guess you can run into all sorts of odd problems. I've never AI'd a standard case but belts work good.

7mm Mashburn Super from 300 Win Mag using COW. No problem.

This is what I did with the .280 RCBS when making brass out of .270 Brass. Up to .308 and back down to .284 to just a snug fit. Worked great. I used a Lee expander in my universal decapping die, as Lee pins have a good taper to them. miles

It stunk up the garage too.

LOL worst part!

Ill bet it did! I tried it in the basement at first....NOT a good idea!

On the other hand, they worked like a charm to chase away those pesky trick-or-treaters last year. The muzzle blast can be seen a half a block away at night....

An update on the 338-378Wby project,

I don't have the rifle in hand and I was running out of time so I gave up the dream of setting a false shoulder with a .358 expander to control where the case would expand with a COW load.

I had to resort to "load and shoot as is" and see if they would form nicely.
The brass is new 30-378 necked up to .338 and they all formed perfectly.
The shoulder pushed forward ~.023" to fit the chamber with no signs of stretching or separating internally.

He's fired factory Wby. ammo in this rifle so I didn't expect any anomalies or pressure spikes with my loads and sure enough, velocities with my loads were within 10fps of loads listed by Barnes, Hodgdon and Nosler.
That velocities were so close to those listed was a surprise.
I have another 40 new cases to form so I'll do some COW loads as first planned just because I'm curious and want to compare.
So far it seems that with new cases, in this rifle, I can load and be done.

Thanks for the thoughts, advice, and reasoning you all offered, I do appreciate it!

Thanks for the follow-up report.

A long time ago I used Cream of Wheat -early 1980's - 7 TCU cases out of military 223 cases.

I've not tried it since. I've improved 270 cases by making them 280 cases. I've also made 350 Rem Mag cases out if 'standard' mag cases. And 7mm-08 cases out of 243 cases. 338 Win Mag out of 7mm Rem Mag cases. I've tried to make 22-250 cases out of 30-06 cases - just because. Plus I've made 256 win mag out of 357 cases. There's other I suppose, only the 7 TCU were required to be reformed. The others lots of cheap brass that I wanted to use in other chamberings.

With belted and rimmed cases it was a snap. Others I used cast bullet loads and double shoulders AND pushing the bullet hard into rifling. It worked ok.