Thumbs down for the Cobra

Proofing your loaded ammuntion.
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62chevy
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Thumbs down for the Cobra

Post by 62chevy »

The Cobra CA 380 was stove piping and tearing the rims up on my reloads. 2.5 grains of TiteGroup. I figured the extractor was causing the problem as the it was not square but looked like a chipped tooth. Removed it and had to use a Dremel and made it square then ran some dummy rounds through the gun to test function, worked so off to the range. Shot 5 rounds with 2 failures to chamber and all five cases had damage to the rim just not as bad as before.

The first range of choice had the road to under 6 foot of water. I knew a back way in via a 2 track but half way down that muddy trail the flooding was even worse. You have to remember this 2 track is all dirt and half way up a mountain so it's up on hill and down the other side with few places to turn around, Thank Jeep for 4 wheel drive. :lol: So we headed to #2 about 50 miles away. It's nice when you have every day off and can do what you want.
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Re: Thumbs down for the Cobra

Post by Ranch Dog »

You didn't mention the specific load you are using but you might need to increase the charge of the TiteGroup to help with the stove piping. I use to own all the Jimenez Arms pistols and they only cycled well with near max loads.
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Re: Thumbs down for the Cobra

Post by 62chevy »

Thanks RD I'll keep that in mind next time I do some loading. Just not sure where that would be with the new Lee TL-356-95-RF, I'm thinking 2.8 to 3.0. I've shot 2.8 before I modified the extractor and that hurt a bit but if that is what it needs then so be it.
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Re: Thumbs down for the Cobra

Post by Ranch Dog »

62chevy wrote:Thanks RD I'll keep that in mind next time I do some loading. Just not sure where that would be with the new Lee TL-356-95-RF, I'm thinking 2.8 to 3.0. I've shot 2.8 before I modified the extractor and that hurt a bit but if that is what it needs then so be it.
What OAL are you using for the cartridge?
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Re: Thumbs down for the Cobra

Post by 62chevy »

OAL is .934 and the bullet weights 97 grains.
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Re: Thumbs down for the Cobra

Post by Ranch Dog »

I ran the numbers through QuickLoad…

Cobra CS 380 Auto
Barrel length: 2.8"
SAAMI groove: .355"

Lee TL356-95-RF
Bullet Length: .405"
Cartridge OAL: .934"

Max Charge of TiteGroup at 70°
Grains: 3.2
Case Fill: 55%
Velocity: 886 FPS
Pressure: 17.1K PSI
Recoil Energy: 2.33 Ft/Lbs
Powder Burnt: 97%

When loading for a semi-auto pistol, I usually consider recoil energy as much as anything else. The best way to determine what the innards of any given pistol was designed to operate at is to look at the SAAMI bullet weight vs. velocity chart for the cartridge. In the case of the 380 Auto, the weight/velocity calculations all work out to 2.50 Ft/Lbs of recoil energy.

Your 2.5-grain load of TiteGroup was only generating 1.52 Ft/Lbs. When handloads are used, most cycle problems with semi-autos are light load related.

Once you shoot and chronograph the load, you might be able to bump the charge .1-grain but that would be the absolute limit. Your ES velocity from a 10-shot string would need to remain within 5% of average (44 FPS) to take the increase. The extreme spread of the chronograph string is telling me how well the pressure extreme spread is behaving. Funny thing is that the bump to 3.4-grains of TiteGroup would produce 2.50 Ft/Lbs of recoil energy! Funny how the math always works out!
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Re: Thumbs down for the Cobra

Post by 62chevy »

Thanks RD I'll work up to the 3.2 grains and see what happens.

I wanted 2.4 because I'm a tight wad and just wanted to stretch my powder.
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Re: Thumbs down for the Cobra

Post by Ranch Dog »

62chevy wrote:Thanks RD I'll work up to the 3.2 grains and see what happens.

I wanted 2.4 because I'm a tight wad and just wanted to stretch my powder.
Well in that case, try 3.0-grains and see it that will work. In this small pistols with a SAAMI spec load, the #1 problem with feed issues is a less than positive grip. You have to give that little bit of recoil energy something to act against. This issue usually surfaces not with "small" shooters, but guys with big hands. They have problems holding the small stocks.

A cook that worked in a desert mule deer hunting camp I frequented carried the Cobra CS. No telling how many times in had been pointed at someone. You see as all the hunters left the camp, he was quite isolated throughout the day, with many of the hunters being up to 25 miles away. Those traveling north through this tough border country well knew there was food & water to be had at the ranch headquarters and the easiest approach was during the day. He shot the CS frequently while we were in camp.
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Re: Thumbs down for the Cobra

Post by 62chevy »

Limp wristting might be my problem as the darn slide has made me bleed more than once. I really need to find some thin leather gloves to shoot this gun with.
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