I'm working with my first wildcat round a .280 GNR which is a necked down and improved .405 Win case. Performance from an Encore pistol is about the same as a .280 AI. I followed Reeders fire form loads of 50 grains of H4350 and 140 grain bullet I did however substitute a LR primer for the LRM primer in his data. Accuracy was so-so @ 50 yards, but I'm blaming that on me as this is my first attempt into a pistol platform for hunting.

I was forming the last 20 unformed rounds that I got when I picked up this barrel. Out of that 20 rounds I had 11 cases formed perfectly. 8 had splits in the shoulder, but the one that worried me the most had a large dent in the body.

What would cause this to happen?

I would suggest you have a couple problems.After necking down the 405 cases to 7mm you have now work hardened the necks. The hard necks are resulting in the necks splitting when fired. The large dent in the body is likely a combination of hard necks and low pressure. Normally the neck should be annealed so it is quite soft. This allows the neck to expand easily and form the gas seal between the neck of the case and the chamber wall.If the neck is too hard or if the chamber pressure is too low that seal is not made properly and some gas gets by the neck. This gas created the large dent in the side of the case. To correct your problem I would suggest you anneal your cases before you fireform them. Your fireform load is quite mild and you switching from a mag primer to a std primer made it milder yet. That likely contributed to your problem. Hope that helps

I was thinking I should have increased the load, but I did call Gary Reeder and asked about the primer swap and annealing. The reason I substituted the primer is because I simply can't get any right now. Gary didn't think I needed to increase the grains of powder however or anneal the cases. Since the brass is over $1 each I hated ruining that many. I've got 29 pieces so hopefully that will last me enough to see if I'm going to like this cannon or not.

anneal em BEFORE and after forming

taylorce If you don't anneal the 29 cases you have left you will loose more the next time you fire them. Just put 3/4 to 1 inch of water in a metal tray (an old cake pan works fine),stand the cases in the water .heat the neck/shoulder area with a small propane torch, until the case just starts to turn a dull red colour. Tip the case over in the water with a small screwdriverand presto your case is annealed. Just make sure you give them a little time to dry out inside.

quote:

Originally posted by jeffeosso:
anneal em BEFORE and after forming

Best advice right there. You are wrok hardening the brass quite a bit by necking it down that far & then fireforming.

Use a somewhat short load of a slower burning powder.

If I understand, you had shoulder splits, not neck splits and one body dent, all upon firing for the first time. Shoulder splits like that are usally a sign of too low pressure during fireforming. It's very common. Using LRM primers probably ups the pressure enough to prevent it. Otherwise you need a different load.

That will happen even with properly annealed cases because they need a sharp peak pressure to fill out the shoulder. Otherwise the material tears trying to stretch. I can't guess about the body dent. Snowman's explanantion sounds logical to me.

Low pressure during fireforming is a BAD thing.

quote:

Originally posted by tiggertate:
If I understand, you had shoulder splits, not neck splits and one body dent, all upon firing for the first time. Shoulder splits like that are usally a sign of too low pressure during fireforming. It's very common. Using LRM primers probably ups the pressure enough to prevent it. Otherwise you need a different load.

That will happen even with properly annealed cases because they need a sharp peak pressure to fill out the shoulder. Otherwise the material tears trying to stretch. I can't guess about the body dent. Snowman's explanantion sounds logical to me.

Low pressure during fireforming is a BAD thing.

Yes I had shoulder splits not neck. Next time I fire form I'll bump up the charge by a grain or two as I still haven't got any LRM primers. Still waiting on Graf's to fill my back order.

Thank you everyone who posted, learned a lot in the few post I received.

I agree with earlier posters...increase your charge and I found with my 280 AI I need to seat the bullets into the lands to force the case back against the bolt....that will ensure you don't get body dents too.

Good luck

quote:

Originally posted by Paul Reed:
I agree with earlier posters...increase your charge and I found with my 280 AI I need to seat the bullets into the lands to force the case back against the bolt....that will ensure you don't get body dents too.

Good luck

Barrel has a lot of free bore, I can't even seat 140 grain bullets to the lands. I imagine that this is how I get .280 AI velocities out of a 17" barrel. Thanks for the suggestion as well.

quote:

but the one that worried me the most had a large dent in the body.

What would cause this to happen?

The neck did not expand. Magnums sometimes do this. A faster burning rate of powder is needed. More pressure.

Split shoulder, too much headspace