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  #1  
Old 12-27-2019, 08:20 PM
5pins 5pins is offline
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Cor Bon .357 Sig 125gr JHP in Clear Ballistics Gel



Test Gun: Sig P229.
Barrel length: 3.9 inches.
Ammunition: Cor Bon .357 Sig 125gr JHP
Test media: 10% Clear Ballistics Gel. Distance: 10 feet. Chronograph: Caldwell Ballistic Precision Chronograph G2. Five shot velocity average: 1397fps
Gel Temperature 70 degrees.

Itís been a long time since I used Cor Bon ammo. Back in the late í80s, it was my load of choice in the 9mm. A lot has changed since then and ammo today is no exception. At the time their 115gr JHP +P was the cats meow so to speak. If my chronograph at the time was to be believed I was getting almost 1300fps out of my Glock 19.

This test was the first time I have shot any Cor Bon in forever but I decided to pick up some in my recent ammo buying spree. Itís also been a while since I tested any .357 Sig, so I got it in that caliber. As we will see, it was unfortunately wrought with problems.

I got a five-shot average velocity of 1397fps with a high of 1493 and a low of 1355fps. Thatís a 138fps extreme spread.


Five shot at ten yards offhand.

When picking up the fired cases I noticed that one of the cases had blown a primer. At that point, I decided to check every case as it came out of the gun.



The first round across the chronograph had a velocity of 1335fps, and when I picked up the case it had a noticeable crack around it about midway up the case. It was also visible on the inside of the case as well.





At this point, a smarter man would have stopped, but Iím not a smarter man and decided to move forward. There were no other blown primers or cracked cases for the rest of the four rounds.

The first round into the bare gel had a velocity of 1410fps and penetrated to 16 inches. The recovered weight was 91 grains and it expanded to .48 inches. Round two. Wait, what happened to round two. The round would not chamber and I discovered the previous round had a case head separation and the front portion was still in the chamber. I tried to find the case from the first shot before loading the second but I couldnít. I finally found the back portion the case after looking some more.





At this point, I became a smarter man and stopped. After getting the front half of the case out of the chamber I fired 20 rounds of some Sig FMJ and a few Sig V-Crown I had left over. There was no blown primes or cracked cases.
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  #2  
Old 12-28-2019, 09:56 AM
SA Inc SA Inc is offline
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Head space issue? Although blown primer may be pressure?
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  #3  
Old 12-28-2019, 10:58 AM
KCJeep KCJeep is offline
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Wow. Thanks for posting. What happened to Corbon????

I just bought my first Corbon ammo, 38 Super 115 jhp and they look and hand cycle fine. Extremely susceptible to bullet set back however.

I have not shot them yet, I'm not so sure I will now.

My preferred ammo carry brand has been Underwood for quite some time. However Underwood only loads .45 in +p stuff which I don't want in my allow framed 1911.
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Old 12-28-2019, 11:51 AM
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My department won't allow Cor-Boom in our guns for this very reason.
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  #5  
Old 12-28-2019, 03:25 PM
SuperMan SuperMan is offline
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I carried the CorBon 115s in my Commander for probably 10 years... Ended up switching to PowR'Ball and now Underwood Xtreme Defender.

The 115s ran from 1450-1495 out of the Commander depending on the lot...at the time they had EXTREMELY low velocity spread. Both PowR'Ball and the XD run in the 1560 fps area from a 4.25" barrel.

From what I have read, the original ower of CorBon sold the business in the last year or so. May explain some things...

Bob
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Old 12-28-2019, 03:28 PM
SuperMan SuperMan is offline
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5pins...if you have time, drop the barrel out of the SIG and drop a round into the chamber to see how the headspace is...my guess is there is something off and with a high pressure bottleneck case like that the case is stretching and separating...

Bob
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  #7  
Old 12-30-2019, 03:26 PM
5pins 5pins is offline
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I have a headspace gauge on the way and I will let everyone know what I find.
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Old 12-31-2019, 09:52 AM
slayer61 slayer61 is offline
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The neck on all those pieces of brass look awful long for 357 Sig, don't they? The neck length almost looks like 9X25. Maybe it's just the angle of the picture???
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Old 12-31-2019, 02:10 PM
5pins 5pins is offline
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Quote:
Originally Posted by slayer61 View Post
The neck on all those pieces of brass look awful long for 357 Sig, don't they? The neck length almost looks like 9X25. Maybe it's just the angle of the picture???
When held side by side with some other .357 Sig ammo the shoulder looks a little different. I tried taking a picture of it but it doesn't come out well enough.
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Old 12-31-2019, 02:15 PM
5pins 5pins is offline
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Well, the gauges came in and the pistol checks out fine. So it's not a headspace issue.
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Old 01-04-2020, 10:03 PM
SuperMan SuperMan is offline
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...not the gun...the ammo....

The SIG is supposed to headspace on the case mouth, not the shoulder. That's why I asked you to drop a round in the chamber to see if it is the correct length or does it drop down too far...

Bob
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Old 01-05-2020, 08:28 AM
hardluk1 hardluk1 is offline
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Clean pistol with a lubed barrel by chance for thos first couple rounds fired at least ? Big spread in velocity to . Hum Have not used corbon in years ether . Underwood guy when faster is wanted .
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  #13  
Old 01-05-2020, 09:47 AM
5pins 5pins is offline
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Quote:
Originally Posted by SuperMan View Post
...not the gun...the ammo....

The SIG is supposed to headspace on the case mouth, not the shoulder. That's why I asked you to drop a round in the chamber to see if it is the correct length or does it drop down too far...

Bob
I did drop a round in the chamber and it looked fine.
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Old 01-05-2020, 09:52 AM
5pins 5pins is offline
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Quote:
Originally Posted by hardluk1 View Post
Clean pistol with a lubed barrel by chance for thos first couple rounds fired at least ? Big spread in velocity to . Hum Have not used corbon in years ether . Underwood guy when faster is wanted .
It hadn't been cleaned recently and the first round's velocity was the lowest (1335) followed by the seconds which was the highest (1493). Also, the lowest velocity was the one with the cracked case.
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  #15  
Old 01-05-2020, 05:55 PM
Ed_Gordon Ed_Gordon is offline
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Caution Will Robinson! Never seen a crack like that even on warn out .357 magnum revolver brass.
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  #16  
Old 01-05-2020, 06:49 PM
PaperTarget PaperTarget is offline
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Very interesting. Thanks for posting this. (And thanks for posting info on other rounds too!) What is the lot code or date of manufacture. Has CorBon identified the cause?
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Old 01-06-2020, 06:39 AM
SuperMan SuperMan is offline
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I actually had some factory remanufactured .357 SIG from a big national company that blew the entire case heads off when fired in a G40.

Fortunately it was a radial failure like above instead of the typical case web blow out that directs all the pressure down into the frame usually cracking it... Blew the extractor off but that was it... Sent the ammo back and they refunded all my money.
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  #18  
Old 01-06-2020, 08:51 AM
hardluk1 hardluk1 is offline
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Contact corbon and send photos and get some feed back .
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Old 01-07-2020, 10:02 AM
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Quote:
Originally Posted by SuperMan View Post
...not the gun...the ammo....

The SIG is supposed to headspace on the case mouth, not the shoulder. That's why I asked you to drop a round in the chamber to see if it is the correct length or does it drop down too far...

Bob

Yeah, just like belted rifle cases are supposed to headspace on the belt. Anybody who has ever tried that has found out quickly that you'll get head separations doing it that way. Same with rimmed cases. If it has a shoulder then use the shoulder to headspace and only bump the shoulder back a couple thou. Most handguns using bottlenecked ammo have this problem until the owner figures out where to size the shoulder.
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