.400 CorBon
Everything
You Ever Wanted To Know

Written and Contributed By Peter Jordan
 

The new 400 Corbon is a drop-in barrel replacement for 45 caliber pistols. The 45/400 Corbon combo actually gives more versatility than the 40s&w/ 357Sig combo. I say this because you can shoot supersonic rounds with both the 40s&w and the 357Sig. But with the 45, you can shoot really large, fat, subsonic bullets that produce excellent momentum for maximum knock down power (with the flexibility of using a silencer); or you can shoot lighter supersonic rounds in the new 400 Corbon format, to give maximum knock down power at the other end of the spectrum, using very high energy and lighter bullets. You have a bullet range of 135 grains to 300 grains!
 

I need to mention one thing before continuing. I personally know a few 10mm fans who don't like the 400 Corbon because the 10mm can do everything the new 400 Corbon can do. So it appears that the 10mm is getting snubbed again; it happened once before with the 40S&W introduction because the 40 could fit into smaller frame guns. Now all of a sudden, there is a new drop-in barrel that simulates a 10mm for the huge flock of 45 owners and you don't even have to buy another gun in the process. I have heard some people claim that the shorter 45 case can feed a little better and even faster than the longer 10mm round; but this is second hand information at best. All I can say is that Colt and Glock are still supporting the 10mm and it is probably the most versatile SINGLE CALIBER of all, from light to heavy loads, from stopping bad guys to being a great back-up trail gun. Glock has even made history by coming out with their 10mm compact, the Glock 29 be mid 1997.
 
 

Now back to the 400 Corbon.....
 

As of January 1997, Starline beefed up the 400 Corbon brass, even though it wasn't really necessary; the brass weighs about 10 grains more now -- aprox 94.5 grains, compared to the older brass weighing in at around 84 grains. The tough bottle-necked case of the 400 Corbon, in conjunction with the new modern 400 Corbon barrel standard, can handle full power Corbon factory loads (using powder unavailable to reloaders), with pressures up to 26,500 psi. One of Corbon's goals was simply to match 10mm specs with the 135 grain bullet, not necessarily to supercharge it beyond those specs. In this way the 45 Auto can be used without making major changes; just drop in a barrel.

In fact, the standard .45 has two SAAMI standards: 21000 psi for standard loads, and 25000 psi for .45+ loads. The top full-power factory 400 Corbon loads just slightly exceed the .45+ standard. It should be noted that most of the starting 400 Corbon loads with a 5" barrel still make the IPSC Major Power Factor, even without stressing the caliber's upper limits.

A Corbon rep told me that they gave the 400 Corbon to the market and have no patents on this cartridge whatsoever. Eventually, someone with several thousand dollars may even have SAAMI set a standard for it. Since Corbon is not a member of SAAMI, I doubt if Corbon will make the effort. But since the 400 Corbon is beginning to generate momentum, and some gun companies like Olympic Arms and AMT are making pistols for this new cartridge, and along with all the barrel makers furnishing 400 Corbon barrels, someone might get together to legitimize this new cartridge yet.

I ran into a Glock Rep at the end of February, in Portland, OR. He stated that Glock was not only coming out with a 357 Sig, but also the 400 Corbon. We'll see .....

Corbon markets a 135 grain 40/10mm bullet that is pushed to 1450 fps according to the ammo box --- not bad for a low pressure 45 huh? It's somewhat like having a 45 and a 10mm in one gun. The 400 Corbon is a unique supersonic round since it uses a pressure ceiling of only 26,500 psi.

I've started getting some reports that the 400 Corbon makes a great hunting pistol, especially as a back-up trail gun. But that's probably an article that someone else can write when more data comes in.

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Personal 400 Corbon Experience:

I put a Bar-Sto 400 Corbon barrel into a Colt .45 Gold cup, along with a 20 lb recoil spring. I must say that the perceived recoil was similar to the typical hotter .45 loads I've shot -- a little snappy but manageable. I have not had the opportunity yet to shoot this new round in 150, 155, or 165 grain loadings. This is a fun caliber to shoot since it has a real head turning roar, and appears to be quite accurate. I have not had even one mis-feed or ejection problem while shooting the 400 Corbon round; this alone makes it very enticing.

A new unfired 400 Corbon cartridge had a lower brass diameter of .472. After firing it, the brass expanded to only .475 in the Bar-Sto barrel. This is quite excellent, especially since I was using an unramped Colt barrel. Even though I shot full power loads, the fired brass was still within trim specs.

I'm also getting a 3.78" 400 Corbon barrel made for my Glock 30, hopefully in early August '97.

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Fact Sheet from Corbon:

1. "The 400 Corbon brings the veteran .45 into the next century with increased velocity and lighter bullet weights." This new caliber is a 45 necked down to a 40.

2. "The distinctive bottleneck cartridge provides additional case capacity, improved feeding, and with headspacing off the shoulder, a tighter bullet crimp can be used to get more efficient powder burning."

3. I don't know which pistol the following chronograph info came from. My guess is a 5" 1911 barrel with a Glock 21 4.6" barrel not far behind in velocity:

   135 JHP          1450 fps     630 ft/lbs    197 power factor
   155 Bonded HP    1330 fps     608 ft/lbs    206 power factor
   165 JHP          1300 fps     581 ft/lbs    214 power factor
   180 JHP          1200 fps (not advertised by Corbon anymore)

Note: These are the bullet weights recommended by Corbon, although I have heard of others experimenting with heavier bullets with good results. Some have even experimented successfully with using very hard lead cast bullets, though Corbon recommends using only jacketed bullets. I can't help wondering if Corbon stopped marketing the 180 grain load because it had no significant velocity advantage over their 185 grain +45 round which pushes a bullet at 1150 fps.

4. "The performance level of this new cartridge rivals the time honored 357 Magnum or the hottest loads in the 10mm." That's a quote.

5. Peter Pi states "The 400 Corbon is a logical selection for federal agencies and special operations forces. I also think that the competition shooters will adopt this round rapidly for IPSC major class matches. Its design is sure to appeal to the officer that likes the control and feel of the standard .45 ACP, but is looking for a round that has the added velocity necessary to make the modern hollow point bullet work effectively." The new IDPA, International Defensive Pistol Association, actually lists the 400 Corbon as one of the legitimate rounds to use in their Enhanced Service Pistol Division.

6. "Availability of components is a key criteria for a cartridge to become successful. Pi ... instead concentrated on developing an improved cartridge using existing components."

7. There is a huge number of quality .45ACP guns available, with custom gun smiths working on the .45's probably more than any other caliber.

8. "The 400 Corbon maintains the same chamber pressures as the 45 ACP +P, and thus does not need special modifications to the springs or guide rods." Most 45's can be converted with a simple drop in barrel change.

9. The brochure states that major firearm manufacturers are already committed to marketing the barrel conversions and complete guns.

10. Reamers and head space gauges are being manufactured by JGS and Clymer. Dies are available from RCBS, Hornady, and Tombstone. Starline is now manufacturing 400 Corbon brass. You can also get a $45 cannulure tool from CH Tool & Die to make sure you have the strongest possible crimp.

11. Advantages: a. added velocity and power for encounters on the open highway.
c. IPSC shooters claim that the added velocity and lighter bullets.
increases scores by reducing the reaction time.

(Call Corbon if you want your name added to their list)

Barrels and conversions:

Accu-Match
Les Baer Custom Inc.
Nowlin
Bar-Sto Precision Machine
Jarvis Gunsmithing
Clark Custom Guns
SSK Industries
Olympic Arms
CH Tool & Die -- cannulure tool

Die sets:

RCBS
SSK IND
Hornady
Tombstone -- Carbide die set - PH: 602-905-7013

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RELOADING:

I received some 400 Corbon reloading data in the mail from Corbon. I'm printing it here, but I take NO responsibility for typos or inaccurate data. Use at your own risk. Call Corbon to get an official copy for yourself (800-626-7266).

With a 5" barrel, even the starting loads are close to, or exceed, the IPSC Major Power Factor of 175. The Power Factor for the Enhanced Service Pistol Division of IDPA is only 125.

TEST gun: Les Baer - Premier II 5" barrel, Brass: Starline, Primer: CCI primer

135 JHP                  Starting                 Maximum           
-------                  grains   velocity  P.F.  grains   velocity  P.F.
-------                  -------- -------- -----  -------  -------- -----
Winchester WAP           10.0     1260     170    11.0     1400     189
Winchester WSF            8.5     1200             9.8     1325
Winchester 540           12.0     1300     176    12.7     1400     189
Hodgdon HS-6             11.5     1240            12.5     1350
Hodgdon Universal Clays   8.2     1260             9.0     1400 
Vihtavuori N-340          8.5     1300             9.7     1400

150/155 JHP              Starting                 Maximum           
-------                  grains   velocity *P.F.  grains   velocity *P.F.
-------                  -------- -------- -----  -------  -------- -----
Winchester WAP            9.8     1225     184    10.5     1310     197
Winchester WSF            7.8     1150             8.2     125
Accurate Arms AA #7      13.0     1250     187    14.0     1300     195
Vihtavuori N-105         11.2     1150            12.0     1250 
*Power factors in this section are based on the lighter 150 grain bullet.

165 JHP                  Starting                 Maximum           
-------                  grains   velocity  P.F.  grains   velocity  P.F.
-------                  -------- -------- -----  -------  -------- -----
Winchester WSF            7.6     1050     173     8.2     1150     190
Vihtavuori N-105         10.5     1125     186    11.2     1250     206
Accurate Arms AA #5       9.0     1025            10.0     1200

Corbon states that they use powders that are NOT available in canisters for reloading. So their factory loads have slightly higher velocities:

  Corbon 135 gr jhp  1450 fps   630 ft/lbs   195 P.F.
  Corbon 155 gr jhp  1330 fps   608 ft/lbs   206 P.F.
  Corbon 165 gr jhp  1300 fps   581 ft/lbs   214 P.F.
  Corbon 180 gr jhp  1200 fps   (not advertised by Corbon anymore)

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The Following Quotes are from the Corbon brochure:

It was the goal of designer Peter Pi to make this cartridge design simple and functional. For most guns a simple drop-in barrel is all that is needed to convert a .45ACP to the 400 Corbon. It is possible to make the 400 Corbon from existing .45ACP brass, however formed brass with the correct headstamp is available from Starline and is recommended. This is especially true since the newer beefed up 400 Corbon brass from Starline is now available.

"Because the 400 Corbon headspaces off the shoulder, it is important to maintain a distance from the base to shoulder midpoint (datum line), of min .717", max .725". This dimension should be monitored carefully throughout the forming or sizing process. We suggest that a tight bullet crimp be used. A roll crimp gives a much more effective hold than a taper crimp and is highly recommended. It is usually not necessary to bell out the case mouth for bullet seating. Excessive belling of the case mouth may make it difficult to maintain a strong tension on the bullet when crimping. Overall length of finished cartridge should be no longer than 1.225".

If you're not into the above method of measuring the base to shoulder midpoint, the overall brass length should stay within the range of .895 to .900 in length. One person stated that he fired the 400 Corbon brass nine times without needing to trim the brass. Never reuse brass beyond safe limits. One reloding book I read stated that you should check the brass after each firing and that you can possibly use it up to eight times, but to throw it away if you are in doubt. Picking up brass on the range can be hazardous since you don't know the history of that brass. The brass is the weak part of the gun and it is always best to use caution when reloading.

A little extra work is required since the 400 Corbon is bottle necked. You must first do a quick light spray lube of the brass, before starting the reloading process. And at the end of the process, you must wipe off the lube, or as an alternative, tumble dry the brass for about 10 minutes. The bright side of lubing is that my Dillon press runs smoother and the Over-All-Length of the cartridges have much tighter specs -- usually within 5/1000 deviation, instead of the normal 5/1000 to 12/1000 deviation when using unlubed cases, although inconsistent bullet shapes can also cause deviations.

For bottle necked cases, you have to always check for trim length as well as lube the brass before reloading; this is generally blasphemy for straight- walled pistol reloaders, but a true art form for the initiated. Gun companies who don't like reloaded ammo in their guns, should flock to the new 400 Corbon and 357 Sig calibers since there is a better chance that not as many pistol shooters will want to reload bottle necked cartridges.

I also recommend expanding the brass as little as possible so the bullet just barely fits in. I found that a very light bell expansion is necessary or else there is a tendency to collapse the brass. Use a firm roll crimp to lightly indent the bullet with a very visible crimp ring. If a carbide resizer is used, you do not need any lube inside the neck, which will also help the bullet from slipping. You only have a little over 1/8" of case surface to grab the bullet. Make sure you use a bullet that can withstand supersonic speeds, such as full metal jacketed bullets.

Lastly, I like to do a thumb pressure test (pushing on the primer end with the thumb while the bullet end is on a hard surface). You want to make sure the bullet is well seated and does not slip into the case, which could cause severe over-pressure conditions. Another test you can do is to load a magazine and then use the full force of the slide going forward to cycle all the bullets through your gun, without pulling the trigger OF COURSE. Measure the before and after Over All Length, to make sure the bullets are not slipping into the case. Do this test a few times to really make sure.

Once your die set is set up, an occasional double check of your cartridge measurements and thumb pressure test is all that is necessary, to make sure the cartridges stay within specs.

Corbon recommends ordering a cannulure tool from CH Tool & Die (about $45) in order to assure a firm bullet crimp, although with the new improved 400 Corbon brass as of January '97, the cannulure tool is not necessarily needed. It's up to you. It might depend on the die set brand you are using. The Tombstone carbide die set I use, seems to get the bullet crimp tight enough, although the crimp die is screwed all the way down so it just barely touches the Dillon shell plate, which is the same exact setting for the resizer die!

"The 400 Corbon is a new cartridge design. While extensive testing has been done by Corbon Bullet Co., it has not been possible to test these loads in guns and/or barrels manufactured by all companies. It is extremely important that you begin with the starting loads and test these loads in your gun. Estimated chamber pressure for these loads was obtained by an Oehler Research Model 43 and appropriate test barrels." Note: A Corbon rep told me that they test all their ammo with actual production guns, like Glock, etc.

Calling Corbon, 800-626-7266, can give you information of where to buy die sets, brass, head space gauges, and reamers, as well as give you a listing of gunsmiths and custom gun manufacturers. I have personally ordered Starline brass, Tombstones's Carbide 3 die set, a Bar-Sto barrel.

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Summary

As mentioned above, the .45 pistol now has the flexibility of using big, fat subsonic bullets to produce maximum momentum or lighter supersonic bullets that produce a powerful energy sting. The 40S&W/357Sig combo is really excellent for small to medium size auto frames, while the 45/400 Corbon combo is excellent on medium to large frames.

The new ParaOrdnance P1045 is a new auto showing off a subcompact 45 (10 + 1 rounds; 24 oz alloy, 31 oz all-steel) in a package size somewhat equivalent to the Glock 26/27; and there is the even smaller AMT 45 and 400 Corbon Backup (5.7" long, 4.1" high, 1" thick; 5 + 1 rounds). So the .45 pistols seem to be encroaching on the small to medium pistol market now! Smith & Wesson has come out with the inexpensive compact 457 .45 caliber. The Glock 30 45 compact (6.77" long, 4.75" high standard or 4.45" high optional, 24 oz) is hitting the market in March of '97. And it looks like H&K will be coming out with a single stack compact .45 later in '97 or early '98. Glock will even start producing factory compensated pistols soon, which should alleviate the concern of perceived-recoil sensitive shooters. In fact, I can't tell much difference in recoil between a 40 and 45 in general; maybe it's because the 40's tend to be on slightly smaller frames, or that the 40 recoil has a kind of sharper intense feel to it.

As you can see from this 'yet another new cartridge', the 400 Corbon may prove to be just the ticket to make the venerable 45 ACP one of the most flexible pistols on the market, as it approaches its one hundreth birthday. Fuller states there are three ways to improve stopping power: increase muzzle energy; increase bullet diameter; and move the penetration to 8.4 to 12.4 inches. Manipulating these three factors, is what makes some rounds superior to others in any given caliber. The new .45/400 Corbon duo has tremendous flexibility to work the Fuller Formula to its fullest, using bullets from 135 grains to 300 grains!