Gentlemen:

I am getting case head separation on my .20 Hornet Improved cases on the fourth or fifth firing. Why? Primer pockets are still tight. Loads in which cases are separating are very light. What is the problem. Cases are separating about .330" from base of cartridge. All cases with three or more firings have a bright ring around the entire case at exactly the same place. What is going on?

Thanks,

Jordan

Headspace issue. Back off the sizing die............

Big Stick:

I don't think so. I am fireforming with cereal and pistol powder and getting a good blow out at the shoulder. Then, after each firing, I neck size only. Seems I read somewhere that incipient case head separation can be a problem on Hornet brass unless your chamber is cut very, very close to the average nominal size of your brass at the case head. I miked my brass [new, unfired case] and compared them to fired cases. On average, the fired brass is .0013" larger at the case head than virgin brass. I am wondering if I should have had my chamber cut with a tighter reamer.

What say you Hornet experts?

Jordan

Some thinning may happen when you fire form. The brass has to come from somewhere to fill the shoulder.

I had a problem with splitting shoulders on the .219 improved and I solved that by putting oil on each case that was going to be fire formed before I chambered it. When you do that the case may fill in from the neck or overall length if you will and not the web.

Another thing to check is that the primers are seated below the base of the case and not sticking out a little and pushing the case forward.

Hornet brass is as frail as it comes,so is naturally unforgiving.

In all my K-Hornets my preference is to form with bullets stoutly into the lands,that in harmony with a snug chamber.

I'm getting nice mileage out of my cases,despite my craving for speed.

Your's still sounds like a headspace issue. I'd form a case with a bullet,back of your sizing die and utilize the same load you are experiencing current incipient seperation upon. I'd then denote the case life of both methods against each other.

Would be a quick/easy experiment and you have all tools required on hand and could draw your own conclusions.

Food for thought...........

Big Stick:

Sounds like an intelligent approach. I think I'll try it. In the meantime, I am sitting here thinking of the 400+ rounds of Hornet brass I have cereal fire-formed and realizing it may all be for naught.

Jordan

Jordan,
Hornet is notorious for stretching. I think our compadre has the answer, and I think if you will load your next batch of bullets so they are right up tight against the bore like he did with a mild load, you'll achieve the same result. I'd also see if Lee has a collet die, or, alternatively, neck size from here out. Ku-dude

Jordan,

I weren't wishing doom and gloom upon you.

Personally,I find it comforting to control my own destiny. Rather than grasp at straws,I try to tackle a problem with what I have on hand.

If my suggestion cures your woes,you got her nipped in the buds. If it don't,you can then look elsewhere.

Unfortunately the Hornet is tempermental regarding overly working it's brass,if only a smidge...............

Are the webs thinned on the fire formed brass or not? Stick a feeler wire in one.

Making sure that you headspace off the shoulder, not the rim, after the first shot may help. But, I have found that I get head separations after 5 or 6 rounds from a standard .22 Hornet, and I only size about .25" of just the neck. Hornet brass seems thin and weak, and work-hardens very quickly!!