Fang
09-13-2008, 08:08 PM
High pressure, heavy bullet, semi-auto handgun: Pick two. The last condition applies to all short-recoil locked-breech actions from 1911s to Glocks to Sigs. Browning designed a very durable action, but the fact that the barrel has to unlock from the slide means that there is always some amount of slop between the two parts, even if it's only a tiny bit. As a round fires, it locks the barrel and slide together with pressure like a hydraulic piston, effectively trying to tear the barrel out of the slide. Holding up under pressure isn't an issue, as Browning's design is far stronger than it needs to be; the problem comes when the bullet first meets the rifling. At this point, the mass of the bullet is combined with the pressure behind it to act as a force smashing the barrel forward. Any gap between the locking lugs on the barrel and slide acts as free space, allowing the barrel get a run up on lug engagement and then crash into lockup.
This is a standard feature of the design and is a nonissue provided the lug engagement is sufficient to withstand the combined force of the bullet mass with the cartridge pressure behind it. This is not an issue if using a heavy bullet with relatively little pressure behind it, such as a 230-grain .45 ACP slug at a standard 23,000 PSI. You can also get away with higher pressures if you use a lighter bullet: 9mm's 124 grains at 35,000 PSI is a good example. The problem comes when heavy bullets start getting pushed at high pressure. Then, only the most careful fitting and best materials will prevent the gun from battering itself apart under the forces of, say, a 200-grain bullet at 44,000 PSI.
The last example is a 10mm loading. Although 10mm gets fairly positive buzz for its power and coolness, it's not a very good cartridge from the perspective of designing a gun around it. At 44,000 PSI, its maximum pressure exceeds that of .44 Magnum and starts creeping into rifle territory. Handgun selection for this round is limited because it requires a certain amount of care to build a safe 10mm semi-auto; when built, all but the most heavily-built handguns tend to break. (1911s in 10mm are notorious for shooting themselves apart.) It's not a winning proposition for manufacturers or someone who wants a durable firearm.
For these reasons, I'd written off 10mm and, by extension, moderate-to-heavy weight .40 cal high speed projectiles from a semi-auto. On the last note, I was a bit premature, having not learned of .400 CorBon.
.400 CorBon uses a .45 ACP case necked down to fit a .40 cal projectile and duplicates mid-range 10mm ballistics. Thanks to the larger case, it does so without exceeding 26,000 PSI--well within the healthy range for any semi-auto. Because of its .45 ACP parentage, .400 CorBon works with any .45 ACP firearm outfitted with a replacement barrel, and uses existing magazines. Dies are available and cases can be made from .45 ACP brass. Although reloading is not as easy as other handgun rounds due to the shoulder with its associated need to lube the cases, necked rounds tend to feed more easily, permitting a chamber with greater case support. As a result, .400 CorBon has the potential to generate ballistics that make 10mm look like a ping-pong ball.
The downsides? Well, for one, the case is bulky, taking up as much space as .45 ACP. Not as many fit in a magazine, which was part of the appeal of 10mm. It's a relatively obscure wildcat round, so factory ammo selection is limited to CorBon's offerings, and these are watered down significantly from the round's potential--possibly to avoid competing with CorBon's .45 ACP line. .400 CorBon is harder to reload than other handgun rounds. (To be fair, though, it's no more difficult than other necked cases such as .357 Sig.) It doesn't solve the various recoil-related issues of the 10mm's ballistics, such as slide slap and recoil spring balancing. Finally, it lacks 10mm's futuristic cachet; maybe CorBon could work around that by renaming it "1cm CorBon."
All in all, it's a neat cartridge with some good potential. A minor increase in pressure could make it the 10mm killer, but without becoming a gun killer as well. Just thought you'd be interested in knowing.
This is a standard feature of the design and is a nonissue provided the lug engagement is sufficient to withstand the combined force of the bullet mass with the cartridge pressure behind it. This is not an issue if using a heavy bullet with relatively little pressure behind it, such as a 230-grain .45 ACP slug at a standard 23,000 PSI. You can also get away with higher pressures if you use a lighter bullet: 9mm's 124 grains at 35,000 PSI is a good example. The problem comes when heavy bullets start getting pushed at high pressure. Then, only the most careful fitting and best materials will prevent the gun from battering itself apart under the forces of, say, a 200-grain bullet at 44,000 PSI.
The last example is a 10mm loading. Although 10mm gets fairly positive buzz for its power and coolness, it's not a very good cartridge from the perspective of designing a gun around it. At 44,000 PSI, its maximum pressure exceeds that of .44 Magnum and starts creeping into rifle territory. Handgun selection for this round is limited because it requires a certain amount of care to build a safe 10mm semi-auto; when built, all but the most heavily-built handguns tend to break. (1911s in 10mm are notorious for shooting themselves apart.) It's not a winning proposition for manufacturers or someone who wants a durable firearm.
For these reasons, I'd written off 10mm and, by extension, moderate-to-heavy weight .40 cal high speed projectiles from a semi-auto. On the last note, I was a bit premature, having not learned of .400 CorBon.
.400 CorBon uses a .45 ACP case necked down to fit a .40 cal projectile and duplicates mid-range 10mm ballistics. Thanks to the larger case, it does so without exceeding 26,000 PSI--well within the healthy range for any semi-auto. Because of its .45 ACP parentage, .400 CorBon works with any .45 ACP firearm outfitted with a replacement barrel, and uses existing magazines. Dies are available and cases can be made from .45 ACP brass. Although reloading is not as easy as other handgun rounds due to the shoulder with its associated need to lube the cases, necked rounds tend to feed more easily, permitting a chamber with greater case support. As a result, .400 CorBon has the potential to generate ballistics that make 10mm look like a ping-pong ball.
The downsides? Well, for one, the case is bulky, taking up as much space as .45 ACP. Not as many fit in a magazine, which was part of the appeal of 10mm. It's a relatively obscure wildcat round, so factory ammo selection is limited to CorBon's offerings, and these are watered down significantly from the round's potential--possibly to avoid competing with CorBon's .45 ACP line. .400 CorBon is harder to reload than other handgun rounds. (To be fair, though, it's no more difficult than other necked cases such as .357 Sig.) It doesn't solve the various recoil-related issues of the 10mm's ballistics, such as slide slap and recoil spring balancing. Finally, it lacks 10mm's futuristic cachet; maybe CorBon could work around that by renaming it "1cm CorBon."
All in all, it's a neat cartridge with some good potential. A minor increase in pressure could make it the 10mm killer, but without becoming a gun killer as well. Just thought you'd be interested in knowing.