Hollow base bullets?

[Reloader2]

I'm new to reloading pistol ammo. I've started loading 9 mm ammo with Berry's 115 grain plated RN bullets.
I noticed on the site they offer hollow base bullets as well. What are the advantages and disadvantages of the hollow base?

[Nick_C_S]

A hollow-base bullet will better "obturate." That is, when fired, the back of the bullet will expand out and into the lands and grooves of the barrel; creating a better gas seal and overall increased barrel contact. This maximizes powder efficiency (by minimizing blow-by); and more importantly, accuracy.

At least, in theory, that's what it does.

That's the advantage.

The disadvantage is that it can be too much of a good thing. Hollow based bullets are best used for lower pressure (target type) loads where proper obturation may an issue.

If you're loading within "normal" pressures (general purpose shooting rounds, defense, recoil practice, etc.), a hollow base bullet is probably not necessary - and even counter-productive - because a conventional based bullet will properly obturate at those operating pressures.

[Jim Watson]

Well, that is what a Minie Ball is for.

I don't know if the small cavity in the base of a plated 9mm will obturate much. It would be interesting to fire some into a CSI capture trap and see.

I think the main advantage of a hollow based bullet in a smokeless powder pistol is that it lengthens the bearing surface for a given weight and nose profile.

[Rico567]

I just started loading some of the Berry's .45 ACP 185 gr. hollow base bullets. What was said in the previous post about obturation of the bullet is one reason. Another is that a hollow base bullet is longer than a solid bullet of the same weight. A solid 185 gr. bullet doesn't have a whole lot of surface bearing on the inside of the case. With the HB bullet in .45, this means there's more bullet surface to provide tension on the case, less possibility of setback or other problems. The second reason is why I'm trying them. Also, of course, they've got less lead in them, so they're somewhat less expensive than the 230 gr. bullets I normally buy.

[Nick_C_S]

Another is that a hollow base bullet is longer than a solid bullet of the same weight. A solid 185 gr. bullet doesn't have a whole lot of surface bearing on the inside of the case.

Good catch. ^^ Yes, this is true. ^^

[FrankenMauser]

If you're loading within "normal" pressures (general purpose shooting rounds, defense, recoil practice, etc.), a hollow base bullet is probably not necessary - and even counter-productive - because a conventional based bullet will properly obturate at those operating pressures.

That isn't necessarily true.
If the bullet is of sufficient hardness, it won't obturate, at all. The diameter you start with is the diameter it remains. You can encounter that problem with everything from 'hard cast' lead bullets, to jacketed bullets. So, if you have a groove diameter larger than bullet diameter, performance may be less than ideal; and you'll likely have significant issues with leading, if using cast bullets.

....Which is where hollow base bullets really shine:
Oversize 'bores' (large groove diameters).
Barrels with variable diameter.
Revolvers with tight forcing cones.
Revolvers with chambers tighter than the groove diameter.
Etcetera...


I run Berry's 100 gr HBRNs in a .380 with a ridiculously oversized bore. Even the lands won't engage a .355" projectile through the majority of the barrel; the groove diameter is .358"x.359"; and there's a loose spot in the barrel that's over .360". With 'standard' bullets, I might as well be spitting rocks out of a smooth-bore. Yet, hollow base bullets conform to the contours of those lands and grooves perfectly.


I run hollow base bullets just as 'hot' as their flat base counterparts.
If it's a soft lead hollow base wadcutter, I'm not going to push it to jacketed velocities; but I will push them just as hard as any other soft lead bullet in the same cartridge.
The same goes for the .380... I'm not trying to make major power factor, but I push the HBRNs just as hard as I would with any other plated bullet. (Which, in .380 Auto, is pretty much the same as any jacketed bullet.)

[kerreckt]

I load hollow base exactly the same way I do the regular flat base bullets. I never load to max. The Berry's HBRN(hollow base round nose) TP(thick plate) in 9mm lists the max velocity as 1500fps. I believe they list max velocity on all their TP bullets as 1500fps and their regular plated bullets as 1200fps. This being the case the TP could be loaded to max. and the regular ones very close to max in most cases.

[Unclenick]

The hollow base moves the center of gravity forward, as well. In the case of a wadcutter, this actually makes the bullet statically stable (like an arrow, a finned rocket, or a weathervane), as the center of pressure is then behind the center of gravity, so air pressure tends to push that end to the rear. Most bullet shapes are the other way around and rely entirely on spin stabilization to remain nose-forward and to prevent backward static stability from flipping them around in flight.

I've never had a handgun with such slow rifling twist that the above matters, though. I just thought I'd throw it out there. Static stability is too weak with bullet shapes without fins to stop them from tumbling without a gyroscopic assist, anyway. OTOH, some sub-sonic rifle shooters load spire points and boattails backward if they think the rifling is a little slow. They're aren't going for long range at subsonic velocities anyway, so the resulting big drop in BC doesn't matter to them.

Every dictionary I can find says "obturate" is a verb that means "to seal-off" something. The SAAMI glossary, for example, defines obturation as when a case expands to fill a chamber, preventing propellant gases from blowing back around it. We may similarly obturate a bore by upsetting a bullet outward against the inside of it. But the bullet itself is its own obstruction and does not need to be sealed off and so is not what is being obturated.

I'm not sure how the shooting community acquired the habit of using "obturate" when we mean "upset", but I've been guilty of it, too. It certainly seems to have become a habit of usage unique to our pastime.

[Jim Watson]

If you are shooting a .356" bullet down a .359" barrel, which happens more often in 9mm than the makers would like you to think, you need some obturation or whatever you care to call it. I am just not certain the hollowbase plated bullet will do it.

[zeke]

Got a particular fondness for Win 115 fmjhb, which seem to be accurate in every 9mm tried in, even the ones with the slightly larger bores. Use a close to max charge of a quicker powder. Never tried the Berrys.