Half jacket versus gas check

[Tatume]

It has been said that half-jacket bullets are dangerous because the core tends to separate from the jacket and the jacket lodges in the bore. Why would that be true of half jackets and not gas checks?

[Wayne Smith]

I don't know who said it but it doesn't track for me. As long as the pressure is on the end of the boolit there is no way it can 'separate' in the bore. It is only when the lead is exposed on the base of the boolit that this can happen.

[M-Tecs]

This issue with half jacket core separation is with certain light loads only. Speer use to cover it in their manual. I have never seen it so this is just what I have read.

[ReloaderFred]

Yes, the problem was/is with light loads. It's simple physics that cause the problem. In a light load, the friction between the jacket and the bore can become stronger than the ability of the jacket to hold the rather slippery core in place. When that friction becomes too much, then the core slips out of the jacket and leaves it stuck in the bore, while the core continues on down the bore and exits, due to it's heavier mass.

As long as the velocity is kept above a certain point, there isn't any problem with core/jacket separation.

In the case of a gas check, the small bearing surface of the check doesn't produce enough friction to overcome it's grip on the bullet. And then there's that pressure from the burning powder that keeps pushing on it as well, but some gas checks do separate after leaving the bore, so the pressure is what kept it in place before exiting.

Hope this helps.

Fred

[Ballistics in Scotland]

It isn't so much a matter of the velocity, as the bullet ceasing to accelerate. As log as the bullet is accelerating rapidly, pressure is pushing the half-jacket firmly in place. It might happen with ultra-light fast-powder loads in a rifle.

I think the above is a whole lot more likely if the half-jacket is inadequately crimped in place. The same might happen with a gas-check, I suppose. But what is "dangerous"? Either seems more likely to cause a bulged barrel than danger to the shooter, but I'd think the gas-check is more likely to let you get away with it altogether.

[Lloyd Smale]

ive shot THOUSANDS of speer half jacket bullets through 41s and 44s and never had it happen. My guess is if you ever saw it it was someones swaged bullet that wasn't swaged properly.

[Tatume]

I've never seen it happen, just wondering why the claim is floating around out there. I've shot a lot of Speer 41 caliber 220 grain half jacket bullets myself, without a problem. I'm not a light load shooter, and can't understand how the jackets can lodge in the barrel if there is pressure behind them.

I've also heard that people used to cut the tips off of 30 caliber FMJ bullets. Sometimes these would blow the core and leave the jacket in the bore. I've never seen that happen either, but it is somewhat more plausible. In that case, the jacket is open at both ends. But who knows?

Thanks everyone, Tom

[Ballistics in Scotland]

I've never seen it happen, just wondering why the claim is floating around out there. I've shot a lot of Speer 41 caliber 220 grain half jacket bullets myself, without a problem. I'm not a light load shooter, and can't understand how the jackets can lodge in the barrel if there is pressure behind them.

I've also heard that people used to cut the tips off of 30 caliber FMJ bullets. Sometimes these would blow the core and leave the jacket in the bore. I've never seen that happen either, but it is somewhat more plausible. In that case, the jacket is open at both ends. But who knows?

Thanks everyone, Tom

Those would be factory bullets, and I have shot a lot of the Speer 100gr. Plinker bullet, which amounts to a half jacket covering the contact area, with the edge of the jacket crimped. I think it is amateur attachment of half jackets, surely uncommon nowadays, that produced the trouble.

I don't say it is common or likely. But the pressure in any load is at its peak just in front of the chamber, and declines from there. If it declines too much, and the jacket is loose, it is just possible that bore friction may retard it enough to shed the core.

[44man]

I shot thousands of half jackets I swaged myself with a C&H tool. But I never fooled with walking loads either so I cant say.
But with the advent of the larger pressures, .357 Max, .454 and up into rifle pressures, cores WERE blown out of bullets so they made the magnum bullets with thicker jackets and a better bond to the lead.
A pure core and a half jacket should never be shot from the high pressure guns.

[Lloyd Smale]

never shot them out of a 357 max or 454 but have shot MANY out of 357s, 41s, and 44s and found them to be one of the most accurate jacketed bullets ive found. They do real well on deer sized game too. If they were still available and casting was somehow outlawed id be stockpiling them.

[44man]

They WERE accurate. I bought jackets from Herter's and lead wire, had the core cutter and they were fun to make. The HP's would make a nasty mess out of a chuck or bottles of water.